// SPDX-License-Identifier: GPL-2.0-only
/*
* linux/fs/locks.c
*
* We implement four types of file locks: BSD locks, posix locks, open
* file description locks, and leases. For details about BSD locks,
* see the flock(2) man page; for details about the other three, see
* fcntl(2).
*
*
* Locking conflicts and dependencies:
* If multiple threads attempt to lock the same byte (or flock the same file)
* only one can be granted the lock, and other must wait their turn.
* The first lock has been "applied" or "granted", the others are "waiting"
* and are "blocked" by the "applied" lock..
*
* Waiting and applied locks are all kept in trees whose properties are:
*
* - the root of a tree may be an applied or waiting lock.
* - every other node in the tree is a waiting lock that
* conflicts with every ancestor of that node.
*
* Every such tree begins life as a waiting singleton which obviously
* satisfies the above properties.
*
* The only ways we modify trees preserve these properties:
*
* 1. We may add a new leaf node, but only after first verifying that it
* conflicts with all of its ancestors.
* 2. We may remove the root of a tree, creating a new singleton
* tree from the root and N new trees rooted in the immediate
* children.
* 3. If the root of a tree is not currently an applied lock, we may
* apply it (if possible).
* 4. We may upgrade the root of the tree (either extend its range,
* or upgrade its entire range from read to write).
*
* When an applied lock is modified in a way that reduces or downgrades any
* part of its range, we remove all its children (2 above). This particularly
* happens when a lock is unlocked.
*
* For each of those child trees we "wake up" the thread which is
* waiting for the lock so it can continue handling as follows: if the
* root of the tree applies, we do so (3). If it doesn't, it must
* conflict with some applied lock. We remove (wake up) all of its children
* (2), and add it is a new leaf to the tree rooted in the applied
* lock (1). We then repeat the process recursively with those
* children.
*
*/
#include <linux/capability.h>
#include <linux/file.h>
#include <linux/fdtable.h>
#include <linux/filelock.h>
#include <linux/fs.h>
#include <linux/init.h>
#include <linux/security.h>
#include <linux/slab.h>
#include <linux/syscalls.h>
#include <linux/time.h>
#include <linux/rcupdate.h>
#include <linux/pid_namespace.h>
#include <linux/hashtable.h>
#include <linux/percpu.h>
#include <linux/sysctl.h>
#define CREATE_TRACE_POINTS
#include <trace/events/filelock.h>
#include <linux/uaccess.h>
static struct file_lock *file_lock(struct file_lock_core *flc)
{
return container_of(flc, struct file_lock, c);
}
static struct file_lease *file_lease(struct file_lock_core *flc)
{
return container_of(flc, struct file_lease, c);
}
static bool lease_breaking(struct file_lease *fl)
{
return fl->c.flc_flags & (FL_UNLOCK_PENDING | FL_DOWNGRADE_PENDING);
}
static int target_leasetype(struct file_lease *fl)
{
if (fl->c.flc_flags & FL_UNLOCK_PENDING)
return F_UNLCK;
if (fl->c.flc_flags & FL_DOWNGRADE_PENDING)
return F_RDLCK;
return fl->c.flc_type;
}
static int leases_enable = 1;
static int lease_break_time = 45;
#ifdef CONFIG_SYSCTL
static struct ctl_table locks_sysctls[] = {
{
.procname = "leases-enable",
.data = &leases_enable,
.maxlen = sizeof(int),
.mode = 0644,
.proc_handler = proc_dointvec,
},
#ifdef CONFIG_MMU
{
.procname = "lease-break-time",
.data = &lease_break_time,
.maxlen = sizeof(int),
.mode = 0644,
.proc_handler = proc_dointvec,
},
#endif /* CONFIG_MMU */
};
static int __init init_fs_locks_sysctls(void)
{
register_sysctl_init("fs", locks_sysctls);
return 0;
}
early_initcall(init_fs_locks_sysctls);
#endif /* CONFIG_SYSCTL */
/*
* The global file_lock_list is only used for displaying /proc/locks, so we
* keep a list on each CPU, with each list protected by its own spinlock.
* Global serialization is done using file_rwsem.
*
* Note that alterations to the list also require that the relevant flc_lock is
* held.
*/
struct file_lock_list_struct {
spinlock_t lock;
struct hlist_head hlist;
};
static DEFINE_PER_CPU(struct file_lock_list_struct, file_lock_list);
DEFINE_STATIC_PERCPU_RWSEM(file_rwsem);
/*
* The blocked_hash is used to find POSIX lock loops for deadlock detection.
* It is protected by blocked_lock_lock.
*
* We hash locks by lockowner in order to optimize searching for the lock a
* particular lockowner is waiting on.
*
* FIXME: make this value scale via some heuristic? We generally will want more
* buckets when we have more lockowners holding locks, but that's a little
* difficult to determine without knowing what the workload will look like.
*/
#define BLOCKED_HASH_BITS 7
static DEFINE_HASHTABLE(blocked_hash, BLOCKED_HASH_BITS);
/*
* This lock protects the blocked_hash. Generally, if you're accessing it, you
* want to be holding this lock.
*
* In addition, it also protects the fl->fl_blocked_requests list, and the
* fl->fl_blocker pointer for file_lock structures that are acting as lock
* requests (in contrast to those that are acting as records of acquired locks).
*
* Note that when we acquire this lock in order to change the above fields,
* we often hold the flc_lock as well. In certain cases, when reading the fields
* protected by this lock, we can skip acquiring it iff we already hold the
* flc_lock.
*/
static DEFINE_SPINLOCK(blocked_lock_lock);
static struct kmem_cache *flctx_cache __ro_after_init;
static struct kmem_cache *filelock_cache __ro_after_init;
static struct kmem_cache *filelease_cache __ro_after_init;
static struct file_lock_context *
locks_get_lock_context(struct inode *inode, int type)
{
struct file_lock_context *ctx;
/* paired with cmpxchg() below */
ctx = locks_inode_context(inode);
if (likely(ctx) || type == F_UNLCK)
goto out;
ctx = kmem_cache_alloc(flctx_cache, GFP_KERNEL);
if (!ctx)
goto out;
spin_lock_init(&ctx->flc_lock);
INIT_LIST_HEAD(&ctx->flc_flock);
INIT_LIST_HEAD(&ctx->flc_posix);
INIT_LIST_HEAD(&ctx->flc_lease);
/*
* Assign the pointer if it's not already assigned. If it is, then
* free the context we just allocated.
*/
if (cmpxchg(&inode->i_flctx, NULL, ctx)) {
kmem_cache_free(flctx_cache, ctx);
ctx = locks_inode_context(inode);
}
out:
trace_locks_get_lock_context(inode, type, ctx);
return ctx;
}
static void
locks_dump_ctx_list(struct list_head *list, char *list_type)
{
struct file_lock_core *flc;
list_for_each_entry(flc, list, flc_list)
pr_warn("%s: fl_owner=%p fl_flags=0x%x fl_type=0x%x fl_pid=%u\n",
list_type, flc->flc_owner, flc->flc_flags,
flc->flc_type, flc->flc_pid);
}
static void
locks_check_ctx_lists(struct inode *inode)
{
struct file_lock_context *ctx = inode->i_flctx;
if (unlikely(!list_empty(&ctx->flc_flock) ||
!list_empty(&ctx->flc_posix) ||
!list_empty(&ctx->flc_lease))) {
pr_warn("Leaked locks on dev=0x%x:0x%x ino=0x%lx:\n",
MAJOR(inode->i_sb->s_dev), MINOR(inode->i_sb->s_dev),
inode->i_ino);
locks_dump_ctx_list(&ctx->flc_flock, "FLOCK");
locks_dump_ctx_list(&ctx->flc_posix, "POSIX");
locks_dump_ctx_list(&ctx->flc_lease, "LEASE");
}
}
static void
locks_check_ctx_file_list(struct file *filp, struct list_head *list, char *list_type)
{
struct file_lock_core *flc;
struct inode *inode = file_inode(filp);
list_for_each_entry(flc, list, flc_list)
if (flc->flc_file == filp)
pr_warn("Leaked %s lock on dev=0x%x:0x%x ino=0x%lx "
" fl_owner=%p fl_flags=0x%x fl_type=0x%x fl_pid=%u\n",
list_type, MAJOR(inode->i_sb->s_dev),
MINOR(inode->i_sb->s_dev), inode->i_ino,
flc->flc_owner, flc->flc_flags,
flc->flc_type, flc->flc_pid);
}
void
locks_free_lock_context(struct inode *inode)
{
struct file_lock_context *ctx = locks_inode_context(inode);
if (unlikely(ctx)) {
locks_check_ctx_lists(inode);
kmem_cache_free(flctx_cache, ctx);
}
}
static void locks_init_lock_heads(struct file_lock_core *flc)
{
INIT_HLIST_NODE(&flc->flc_link);
INIT_LIST_HEAD(&flc->flc_list);
INIT_LIST_HEAD(&flc->flc_blocked_requests);
INIT_LIST_HEAD(&flc->flc_blocked_member);
init_waitqueue_head(&flc->flc_wait);
}
/* Allocate an empty lock structure. */
struct file_lock *locks_alloc_lock(void)
{
struct file_lock *fl = kmem_cache_zalloc(filelock_cache, GFP_KERNEL);
if (fl)
locks_init_lock_heads(&fl->c);
return fl;
}
EXPORT_SYMBOL_GPL(locks_alloc_lock);
/* Allocate an empty lock structure. */
struct file_lease *locks_alloc_lease(void)
{
struct file_lease *fl = kmem_cache_zalloc(filelease_cache, GFP_KERNEL);
if (fl)
locks_init_lock_heads(&fl->c);
return fl;
}
EXPORT_SYMBOL_GPL(locks_alloc_lease);
void locks_release_private(struct file_lock *fl)
{
struct file_lock_core *flc = &fl->c;
BUG_ON(waitqueue_active(&flc->flc_wait));
BUG_ON(!list_empty(&flc->flc_list));
BUG_ON(!list_empty(&flc->flc_blocked_requests));
BUG_ON(!list_empty(&flc->flc_blocked_member));
BUG_ON(!hlist_unhashed(&flc->flc_link));
if (fl->fl_ops) {
if (fl->fl_ops->fl_release_private)
fl->fl_ops->fl_release_private(fl);
fl->fl_ops = NULL;
}
if (fl->fl_lmops) {
if (fl->fl_lmops->lm_put_owner) {
fl->fl_lmops->lm_put_owner(flc->flc_owner);
flc->flc_owner = NULL;
}
fl->fl_lmops = NULL;
}
}
EXPORT_SYMBOL_GPL(locks_release_private);
/**
* locks_owner_has_blockers - Check for blocking lock requests
* @flctx: file lock context
* @owner: lock owner
*
* Return values:
* %true: @owner has at least one blocker
* %false: @owner has no blockers
*/
bool locks_owner_has_blockers(struct file_lock_context *flctx, fl_owner_t owner)
{
struct file_lock_core *flc;
spin_lock(&flctx->flc_lock);
list_for_each_entry(flc, &flctx->flc_posix, flc_list) {
if (flc->flc_owner != owner)
continue;
if (!list_empty(&flc->flc_blocked_requests)) {
spin_unlock(&flctx->flc_lock);
return true;
}
}
spin_unlock(&flctx->flc_lock);
return false;
}
EXPORT_SYMBOL_GPL(locks_owner_has_blockers);
/* Free a lock which is not in use. */
void locks_free_lock(struct file_lock *fl)
{
locks_release_private(fl);
kmem_cache_free(filelock_cache, fl);
}
EXPORT_SYMBOL(locks_free_lock);
/* Free a lease which is not in use. */
void locks_free_lease(struct file_lease *fl)
{
kmem_cache_free(filelease_cache, fl);
}
EXPORT_SYMBOL(locks_free_lease);
static void
locks_dispose_list(struct list_head *dispose)
{
struct file_lock_core *flc;
while (!list_empty(dispose)) {
flc = list_first_entry(dispose, struct file_lock_core, flc_list);
list_del_init(&flc->flc_list);
if (flc->flc_flags & (FL_LEASE|FL_DELEG|FL_LAYOUT))
locks_free_lease(file_lease(flc));
else
locks_free_lock(file_lock(flc));
}
}
void locks_init_lock(struct file_lock *fl)
{
memset(fl, 0, sizeof(struct file_lock));
locks_init_lock_heads(&fl->c);
}
EXPORT_SYMBOL(locks_init_lock);
void locks_init_lease(struct file_lease *fl)
{
memset(fl, 0, sizeof(*fl));
locks_init_lock_heads(&fl->c);
}
EXPORT_SYMBOL(locks_init_lease);
/*
* Initialize a new lock from an existing file_lock structure.
*/
void locks_copy_conflock(struct file_lock *new, struct file_lock *fl)
{
new->c.flc_owner = fl->c.flc_owner;
new->c.flc_pid = fl->c.flc_pid;
new->c.flc_file = NULL;
new->c.flc_flags = fl->c.flc_flags;
new->c.flc_type = fl->c.flc_type;
new->fl_start = fl->fl_start;
new->fl_end = fl->fl_end;
new->fl_lmops = fl->fl_lmops;
new->fl_ops = NULL;
if (fl->fl_lmops) {
if (fl->fl_lmops->lm_get_owner)
fl->fl_lmops->lm_get_owner(fl->c.flc_owner);
}
}
EXPORT_SYMBOL(locks_copy_conflock);
void locks_copy_lock(struct file_lock *new, struct file_lock *fl)
{
/* "new" must be a freshly-initialized lock */
WARN_ON_ONCE(new->fl_ops);
locks_copy_conflock(new, fl);
new->c.flc_file = fl->c.flc_file;
new->fl_ops = fl->fl_ops;
if (fl->fl_ops) {
if (fl->fl_ops->fl_copy_lock)
fl->fl_ops->fl_copy_lock(new, fl);
}
}
EXPORT_SYMBOL(locks_copy_lock);
static void locks_move_blocks(struct file_lock *new, struct file_lock *fl)
{
struct file_lock *f;
/*
* As ctx->flc_lock is held, new requests cannot be added to
* ->flc_blocked_requests, so we don't need a lock to check if it
* is empty.
*/
if (list_empty(&fl->c.flc_blocked_requests))
return;
spin_lock(&blocked_lock_lock);
list_splice_init(&fl->c.flc_blocked_requests,
&new->c.flc_blocked_requests);
list_for_each_entry(f, &new->c.flc_blocked_requests,
c.flc_blocked_member)
f->c.flc_blocker = &new->c;
spin_unlock(&blocked_lock_lock);
}
static inline int flock_translate_cmd(int cmd) {
switch (cmd) {
case LOCK_SH:
return F_RDLCK;
case LOCK_EX:
return F_WRLCK;
case LOCK_UN:
return F_UNLCK;
}
return -EINVAL;
}
/* Fill in a file_lock structure with an appropriate FLOCK lock. */
static void flock_make_lock(struct file *filp, struct file_lock *fl, int type)
{
locks_init_lock(fl);
fl->c.flc_file = filp;
fl->c.flc_owner = filp;
fl->c.flc_pid = current->tgid;
fl->c.flc_flags = FL_FLOCK;
fl->c.flc_type = type;
fl->fl_end = OFFSET_MAX;
}
static int assign_type(struct file_lock_core *flc, int type)
{
switch (type) {
case F_RDLCK:
case F_WRLCK:
case F_UNLCK:
flc->flc_type = type;
break;
default:
return -EINVAL;
}
return 0;
}
static int flock64_to_posix_lock(struct file *filp, struct file_lock *fl,
struct flock64 *l)
{
switch (l->l_whence) {
case SEEK_SET:
fl->fl_start = 0;
break;
case SEEK_CUR:
fl->fl_start = filp->f_pos;
break;
case SEEK_END:
fl->fl_start = i_size_read(file_inode(filp));
break;
default:
return -EINVAL;
}
if (l->l_start > OFFSET_MAX - fl->fl_start)
return -EOVERFLOW;
fl->fl_start += l->l_start;
if (fl->fl_start < 0)
return -EINVAL;
/* POSIX-1996 leaves the case l->l_len < 0 undefined;
POSIX-2001 defines it. */
if (l->l_len > 0) {
if (l->l_len - 1 > OFFSET_MAX - fl->fl_start)
return -EOVERFLOW;
fl->fl_end = fl->fl_start + (l->l_len - 1);
} else if (l->l_len < 0) {
if (fl->fl_start + l->l_len < 0)
return -EINVAL;
fl->fl_end = fl->fl_start - 1;
fl->fl_start += l->l_len;
} else
fl->fl_end = OFFSET_MAX;
fl->c.flc_owner = current->files;
fl->c.flc_pid = current->tgid;
fl->c.flc_file = filp;
fl->c.flc_flags = FL_POSIX;
fl->fl_ops = NULL;
fl->fl_lmops = NULL;
return assign_type(&fl->c, l->l_type);
}
/* Verify a "struct flock" and copy it to a "struct file_lock" as a POSIX
* style lock.
*/
static int flock_to_posix_lock(struct file *filp, struct file_lock *fl,
struct flock *l)
{
struct flock64 ll = {
.l_type = l->l_type,
.l_whence = l->l_whence,
.l_start = l->l_start,
.l_len = l->l_len,
};
return flock64_to_posix_lock(filp, fl, &ll);
}
/* default lease lock manager operations */
static bool
lease_break_callback(struct file_lease *fl)
{
kill_fasync(&fl->fl_fasync, SIGIO, POLL_MSG);
return false;
}
static void
lease_setup(struct file_lease *fl, void **priv)
{
struct file *filp = fl->c.flc_file;
struct fasync_struct *fa = *priv;
/*
* fasync_insert_entry() returns the old entry if any. If there was no
* old entry, then it used "priv" and inserted it into the fasync list.
* Clear the pointer to indicate that it shouldn't be freed.
*/
if (!fasync_insert_entry(fa->fa_fd, filp, &fl->fl_fasync, fa))
*priv = NULL;
__f_setown(filp, task_pid(current), PIDTYPE_TGID, 0);
}
static const struct lease_manager_operations lease_manager_ops = {
.lm_break = lease_break_callback,
.lm_change = lease_modify,
.lm_setup = lease_setup,
};
/*
* Initialize a lease, use the default lock manager operations
*/
static int lease_init(struct file *filp, int type, struct file_lease *fl)
{
if (assign_type(&fl->c, type) != 0)
return -EINVAL;
fl->c.flc_owner = filp;
fl->c.flc_pid = current->tgid;
fl->c.flc_file = filp;
fl->c.flc_flags = FL_LEASE;
fl->fl_lmops = &lease_manager_ops;
return 0;
}
/* Allocate a file_lock initialised to this type of lease */
static struct file_lease *lease_alloc(struct file *filp, int type)
{
struct file_lease *fl = locks_alloc_lease();
int error = -ENOMEM;
if (fl == NULL)
return ERR_PTR(error);
error = lease_init(filp, type, fl);
if (error) {
locks_free_lease(fl);
return ERR_PTR(error);
}
return fl;
}
/* Check if two locks overlap each other.
*/
static inline int locks_overlap(struct file_lock *fl1, struct file_lock *fl2)
{
return ((fl1->fl_end >= fl2->fl_start) &&
(fl2->fl_end >= fl1->fl_start));
}
/*
* Check whether two locks have the same owner.
*/
static int posix_same_owner(struct file_lock_core *fl1, struct file_lock_core *fl2)
{
return fl1->flc_owner == fl2->flc_owner;
}
/* Must be called with the flc_lock held! */
static void locks_insert_global_locks(struct file_lock_core *flc)
{
struct file_lock_list_struct *fll = this_cpu_ptr(&file_lock_list);
percpu_rwsem_assert_held(&file_rwsem);
spin_lock(&fll->lock);
flc->flc_link_cpu = smp_processor_id();
hlist_add_head(&flc->flc_link, &fll->hlist);
spin_unlock(&fll->lock);
}
/* Must be called with the flc_lock held! */
static void locks_delete_global_locks(struct file_lock_core *flc)
{
struct file_lock_list_struct *fll;
percpu_rwsem_assert_held(&file_rwsem);
/*
* Avoid taking lock if already unhashed. This is safe since this check
* is done while holding the flc_lock, and new insertions into the list
* also require that it be held.
*/
if (hlist_unhashed(&flc->flc_link))
return;
fll = per_cpu_ptr(&file_lock_list, flc->flc_link_cpu);
spin_lock(&fll->lock);
hlist_del_init(&flc->flc_link);
spin_unlock(&fll->lock);
}
static unsigned long
posix_owner_key(struct file_lock_core *flc)
{
return (unsigned long) flc->flc_owner;
}
static void locks_insert_global_blocked(struct file_lock_core *waiter)
{
lockdep_assert_held(&blocked_lock_lock);
hash_add(blocked_hash, &waiter->flc_link, posix_owner_key(waiter));
}
static void locks_delete_global_blocked(struct file_lock_core *waiter)
{
lockdep_assert_held(&blocked_lock_lock);
hash_del(&waiter->flc_link);
}
/* Remove waiter from blocker's block list.
* When blocker ends up pointing to itself then the list is empty.
*
* Must be called with blocked_lock_lock held.
*/
static void __locks_unlink_block(struct file_lock_core *waiter)
{
locks_delete_global_blocked(waiter);
list_del_init(&waiter->flc_blocked_member);
}
static void __locks_wake_up_blocks(struct file_lock_core *blocker)
{
while (!list_empty(&blocker->flc_blocked_requests)) {
struct file_lock_core *waiter;
struct file_lock *fl;
waiter = list_first_entry(&blocker->flc_blocked_requests,
struct file_lock_core, flc_blocked_member);
fl = file_lock(waiter);
__locks_unlink_block(waiter);
if ((waiter->flc_flags & (FL_POSIX | FL_FLOCK)) &&
fl->fl_lmops && fl->fl_lmops->lm_notify)
fl->fl_lmops->lm_notify(fl);
else
locks_wake_up(fl);
/*
* The setting of flc_blocker to NULL marks the "done"
* point in deleting a block. Paired with acquire at the top
* of locks_delete_block().
*/
smp_store_release(&waiter->flc_blocker, NULL);
}
}
static int __locks_delete_block(struct file_lock_core *waiter)
{
int status = -ENOENT;
/*
* If fl_blocker is NULL, it won't be set again as this thread "owns"
* the lock and is the only one that might try to claim the lock.
*
* We use acquire/release to manage fl_blocker so that we can
* optimize away taking the blocked_lock_lock in many cases.
*
* The smp_load_acquire guarantees two things:
*
* 1/ that fl_blocked_requests can be tested locklessly. If something
* was recently added to that list it must have been in a locked region
* *before* the locked region when fl_blocker was set to NULL.
*
* 2/ that no other thread is accessing 'waiter', so it is safe to free
* it. __locks_wake_up_blocks is careful not to touch waiter after
* fl_blocker is released.
*
* If a lockless check of fl_blocker shows it to be NULL, we know that
* no new locks can be inserted into its fl_blocked_requests list, and
* can avoid doing anything further if the list is empty.
*/
if (!smp_load_acquire(&waiter->flc_blocker) &&
list_empty(&waiter->flc_blocked_requests))
return status;
spin_lock(&blocked_lock_lock);
if (waiter->flc_blocker)
status = 0;
__locks_wake_up_blocks(waiter);
__locks_unlink_block(waiter);
/*
* The setting of fl_blocker to NULL marks the "done" point in deleting
* a block. Paired with acquire at the top of this function.
*/
smp_store_release(&waiter->flc_blocker, NULL);
spin_unlock(&blocked_lock_lock);
return status;
}
/**
* locks_delete_block - stop waiting for a file lock
* @waiter: the lock which was waiting
*
* lockd/nfsd need to disconnect the lock while working on it.
*/
int locks_delete_block(struct file_lock *waiter)
{
return __locks_delete_block(&waiter->c);
}
EXPORT_SYMBOL(locks_delete_block);
/* Insert waiter into blocker's block list.
* We use a circular list so that processes can be easily woken up in
* the order they blocked. The documentation doesn't require this but
* it seems like the reasonable thing to do.
*
* Must be called with both the flc_lock and blocked_lock_lock held. The
* fl_blocked_requests list itself is protected by the blocked_lock_lock,
* but by ensuring that the flc_lock is also held on insertions we can avoid
* taking the blocked_lock_lock in some cases when we see that the
* fl_blocked_requests list is empty.
*
* Rather than just adding to the list, we check for conflicts with any existing
* waiters, and add beneath any waiter that blocks the new waiter.
* Thus wakeups don't happen until needed.
*/
static void __locks_insert_block(struct file_lock_core *blocker,
struct file_lock_core *waiter,
bool conflict(struct file_lock_core *,
struct file_lock_core *))
{
struct file_lock_core *flc;
BUG_ON(!list_empty(&waiter->flc_blocked_member));
new_blocker:
list_for_each_entry(flc, &blocker->flc_blocked_requests, flc_blocked_member)
if (conflict(flc, waiter)) {
blocker = flc;
goto new_blocker;
}
waiter->flc_blocker = blocker;
list_add_tail(&waiter->flc_blocked_member,
&blocker->flc_blocked_requests);
if ((blocker->flc_flags & (FL_POSIX|FL_OFDLCK)) == FL_POSIX)
locks_insert_global_blocked(waiter);
/* The requests in waiter->flc_blocked are known to conflict with
* waiter, but might not conflict with blocker, or the requests
* and lock which block it. So they all need to be woken.
*/
__locks_wake_up_blocks(waiter);
}
/* Must be called with flc_lock held. */
static void locks_insert_block(struct file_lock_core *blocker,
struct file_lock_core *waiter,
bool conflict(struct file_lock_core *,
struct file_lock_core *))
{
spin_lock(&blocked_lock_lock);
__locks_insert_block(blocker, waiter, conflict);
spin_unlock(&blocked_lock_lock);
}
/*
* Wake up processes blocked waiting for blocker.
*
* Must be called with the inode->flc_lock held!
*/
static void locks_wake_up_blocks(struct file_lock_core *blocker)
{
/*
* Avoid taking global lock if list is empty. This is safe since new
* blocked requests are only added to the list under the flc_lock, and
* the flc_lock is always held here. Note that removal from the
* fl_blocked_requests list does not require the flc_lock, so we must
* recheck list_empty() after acquiring the blocked_lock_lock.
*/
if (list_empty(&blocker->flc_blocked_requests))
return;
spin_lock(&blocked_lock_lock);
__locks_wake_up_blocks(blocker);
spin_unlock(&blocked_lock_lock);
}
static void
locks_insert_lock_ctx(struct file_lock_core *fl, struct list_head *before)
{
list_add_tail(&fl->flc_list, before);
locks_insert_global_locks(fl);
}
static void
locks_unlink_lock_ctx(struct file_lock_core *fl)
{
locks_delete_global_locks(fl);
list_del_init(&fl->flc_list);
locks_wake_up_blocks(fl);
}
static void
locks_delete_lock_ctx(struct file_lock_core *fl, struct list_head *dispose)
{
locks_unlink_lock_ctx(fl);
if (dispose)
list_add(&fl->flc_list, dispose);
else
locks_free_lock(file_lock(fl));
}
/* Determine if lock sys_fl blocks lock caller_fl. Common functionality
* checks for shared/exclusive status of overlapping locks.
*/
static bool locks_conflict(struct file_lock_core *caller_flc,
struct file_lock_core *sys_flc)
{
if (sys_flc->flc_type == F_WRLCK)
return true;
if (caller_flc->flc_type == F_WRLCK)
return true;
return false;
}
/* Determine if lock sys_fl blocks lock caller_fl. POSIX specific
* checking before calling the locks_conflict().
*/
static bool posix_locks_conflict(struct file_lock_core *caller_flc,
struct file_lock_core *sys_flc)
{
struct file_lock *caller_fl = file_lock(caller_flc);
struct file_lock *sys_fl = file_lock(sys_flc);
/* POSIX locks owned by the same process do not conflict with
* each other.
*/
if (posix_same_owner(caller_flc, sys_flc))
return false;
/* Check whether they overlap */
if (!locks_overlap(caller_fl, sys_fl))
return false;
return locks_conflict(caller_flc, sys_flc);
}
/* Determine if lock sys_fl blocks lock caller_fl. Used on xx_GETLK
* path so checks for additional GETLK-specific things like F_UNLCK.
*/
static bool posix_test_locks_conflict(struct file_lock *caller_fl,
struct file_lock *sys_fl)
{
struct file_lock_core *caller = &caller_fl->c;
struct file_lock_core *sys = &sys_fl->c;
/* F_UNLCK checks any locks on the same fd. */
if (lock_is_unlock(caller_fl)) {
if (!posix_same_owner(caller, sys))
return false;
return locks_overlap(caller_fl, sys_fl);
}
return posix_locks_conflict(caller, sys);
}
/* Determine if lock sys_fl blocks lock caller_fl. FLOCK specific
* checking before calling the locks_conflict().
*/
static bool flock_locks_conflict(struct file_lock_core *caller_flc,
struct file_lock_core *sys_flc)
{
/* FLOCK locks referring to the same filp do not conflict with
* each other.
*/
if (caller_flc->flc_file == sys_flc->flc_file)
return false;
return locks_conflict(caller_flc, sys_flc);
}
void
posix_test_lock(struct file *filp, struct file_lock *fl)
{
struct file_lock *cfl;
struct file_lock_context *ctx;
struct inode *inode = file_inode(filp);
void *owner;
void (*func)(void);
ctx = locks_inode_context(inode);
if (!ctx || list_empty_careful(&ctx->flc_posix)) {
fl->c.flc_type = F_UNLCK;
return;
}
retry:
spin_lock(&ctx->flc_lock);
list_for_each_entry(cfl, &ctx->flc_posix, c.flc_list) {
if (!posix_test_locks_conflict(fl, cfl))
continue;
if (cfl->fl_lmops && cfl->fl_lmops->lm_lock_expirable
&& (*cfl->fl_lmops->lm_lock_expirable)(cfl)) {
owner = cfl->fl_lmops->lm_mod_owner;
func = cfl->fl_lmops->lm_expire_lock;
__module_get(owner);
spin_unlock(&ctx->flc_lock);
(*func)();
module_put(owner);
goto retry;
}
locks_copy_conflock(fl, cfl);
goto out;
}
fl->c.flc_type = F_UNLCK;
out:
spin_unlock(&ctx->flc_lock);
return;
}
EXPORT_SYMBOL(posix_test_lock);
/*
* Deadlock detection:
*
* We attempt to detect deadlocks that are due purely to posix file
* locks.
*
* We assume that a task can be waiting for at most one lock at a time.
* So for any acquired lock, the process holding that lock may be
* waiting on at most one other lock. That lock in turns may be held by
* someone waiting for at most one other lock. Given a requested lock
* caller_fl which is about to wait for a conflicting lock block_fl, we
* follow this chain of waiters to ensure we are not about to create a
* cycle.
*
* Since we do this before we ever put a process to sleep on a lock, we
* are ensured that there is never a cycle; that is what guarantees that
* the while() loop in posix_locks_deadlock() eventually completes.
*
* Note: the above assumption may not be true when handling lock
* requests from a broken NFS client. It may also fail in the presence
* of tasks (such as posix threads) sharing the same open file table.
* To handle those cases, we just bail out after a few iterations.
*
* For FL_OFDLCK locks, the owner is the filp, not the files_struct.
* Because the owner is not even nominally tied to a thread of
* execution, the deadlock detection below can't reasonably work well. Just
* skip it for those.
*
* In principle, we could do a more limited deadlock detection on FL_OFDLCK
* locks that just checks for the case where two tasks are attempting to
* upgrade from read to write locks on the same inode.
*/
#define MAX_DEADLK_ITERATIONS 10
/* Find a lock that the owner of the given @blocker is blocking on. */
static struct file_lock_core *what_owner_is_waiting_for(struct file_lock_core *blocker)
{
struct file_lock_core *flc;
hash_for_each_possible(blocked_hash, flc, flc_link, posix_owner_key(blocker)) {
if (posix_same_owner(flc, blocker)) {
while (flc->flc_blocker)
flc = flc->flc_blocker;
return flc;
}
}
return NULL;
}
/* Must be called with the blocked_lock_lock held! */
static bool posix_locks_deadlock(struct file_lock *caller_fl,
struct file_lock *block_fl)
{
struct file_lock_core *caller = &caller_fl->c;
struct file_lock_core *blocker = &block_fl->c;
int i = 0;
lockdep_assert_held(&blocked_lock_lock);
/*
* This deadlock detector can't reasonably detect deadlocks with
* FL_OFDLCK locks, since they aren't owned by a process, per-se.
*/
if (caller->flc_flags & FL_OFDLCK)
return false;
while ((blocker = what_owner_is_waiting_for(blocker))) {
if (i++ > MAX_DEADLK_ITERATIONS)
return false;
if (posix_same_owner(caller, blocker))
return true;
}
return false;
}
/* Try to create a FLOCK lock on filp. We always insert new FLOCK locks
* after any leases, but before any posix locks.
*
* Note that if called with an FL_EXISTS argument, the caller may determine
* whether or not a lock was successfully freed by testing the return
* value for -ENOENT.
*/
static int flock_lock_inode(struct inode *inode, struct file_lock *request)
{
struct file_lock *new_fl = NULL;
struct file_lock *fl;
struct file_lock_context *ctx;
int error = 0;
bool found = false;
LIST_HEAD(dispose);
ctx = locks_get_lock_context(inode, request->c.flc_type);
if (!ctx) {
if (request->c.flc_type != F_UNLCK)
return -ENOMEM;
return (request->c.flc_flags & FL_EXISTS) ? -ENOENT : 0;
}
if (!(request->c.flc_flags & FL_ACCESS) && (request->c.flc_type != F_UNLCK)) {
new_fl = locks_alloc_lock();
if (!new_fl)
return -ENOMEM;
}
percpu_down_read(&file_rwsem);
spin_lock(&ctx->flc_lock);
if (request->c.flc_flags & FL_ACCESS)
goto find_conflict;
list_for_each_entry(fl, &ctx->flc_flock, c.flc_list) {
if (request->c.flc_file != fl->c.flc_file)
continue;
if (request->c.flc_type == fl->c.flc_type)
goto out;
found = true;
locks_delete_lock_ctx(&fl->c, &dispose);
break;
}
if (lock_is_unlock(request)) {
if ((request->c.flc_flags & FL_EXISTS) && !found)
error = -ENOENT;
goto out;
}
find_conflict:
list_for_each_entry(fl, &ctx->flc_flock, c.flc_list) {
if (!flock_locks_conflict(&request->c, &fl->c))
continue;
error = -EAGAIN;
if (!(request->c.flc_flags & FL_SLEEP))
goto out;
error = FILE_LOCK_DEFERRED;
locks_insert_block(&fl->c, &request->c, flock_locks_conflict);
goto out;
}
if (request->c.flc_flags & FL_ACCESS)
goto out;
locks_copy_lock(new_fl, request);
locks_move_blocks(new_fl, request);
locks_insert_lock_ctx(&new_fl->c, &ctx->flc_flock);
new_fl = NULL;
error = 0;
out:
spin_unlock(&ctx->flc_lock);
percpu_up_read(&file_rwsem);
if (new_fl)
locks_free_lock(new_fl);
locks_dispose_list(&dispose);
trace_flock_lock_inode(inode, request, error);
return error;
}
static int posix_lock_inode(struct inode *inode, struct file_lock *request,
struct file_lock *conflock)
{
struct file_lock *fl, *tmp;
struct file_lock *new_fl = NULL;
struct file_lock *new_fl2 = NULL;
struct file_lock *left = NULL;
struct file_lock *right = NULL;
struct file_lock_context *ctx;
int error;
bool added = false;
LIST_HEAD(dispose);
void *owner;
void (*func)(void);
ctx = locks_get_lock_context(inode, request->c.flc_type);
if (!ctx)
return lock_is_unlock(request) ? 0 : -ENOMEM;
/*
* We may need two file_lock structures for this operation,
* so we get them in advance to avoid races.
*
* In some cases we can be sure, that no new locks will be needed
*/
if (!(request->c.flc_flags & FL_ACCESS) &&
(request->c.flc_type != F_UNLCK ||
request->fl_start != 0 || request->fl_end != OFFSET_MAX)) {
new_fl = locks_alloc_lock();
new_fl2 = locks_alloc_lock();
}
retry:
percpu_down_read(&file_rwsem);
spin_lock(&ctx->flc_lock);
/*
* New lock request. Walk all POSIX locks and look for conflicts. If
* there are any, either return error or put the request on the
* blocker's list of waiters and the global blocked_hash.
*/
if (request->c.flc_type != F_UNLCK) {
list_for_each_entry(fl, &ctx->flc_posix, c.flc_list) {
if (!posix_locks_conflict(&request->c, &fl->c))
continue;
if (fl->fl_lmops && fl->fl_lmops->lm_lock_expirable
&& (*fl->fl_lmops->lm_lock_expirable)(fl)) {
owner = fl->fl_lmops->lm_mod_owner;
func = fl->fl_lmops->lm_expire_lock;
__module_get(owner);
spin_unlock(&ctx->flc_lock);
percpu_up_read(&file_rwsem);
(*func)();
module_put(owner);
goto retry;
}
if (conflock)
locks_copy_conflock(conflock, fl);
error = -EAGAIN;
if (!(request->c.flc_flags & FL_SLEEP))
goto out;
/*
* Deadlock detection and insertion into the blocked
* locks list must be done while holding the same lock!
*/
error = -EDEADLK;
spin_lock(&blocked_lock_lock);
/*
* Ensure that we don't find any locks blocked on this
* request during deadlock detection.
*/
__locks_wake_up_blocks(&request->c);
if (likely(!posix_locks_deadlock(request, fl))) {
error = FILE_LOCK_DEFERRED;
__locks_insert_block(&fl->c, &request->c,
posix_locks_conflict);
}
spin_unlock(&blocked_lock_lock);
goto out;
}
}
/* If we're just looking for a conflict, we're done. */
error = 0;
if (request->c.flc_flags & FL_ACCESS)
goto out;
/* Find the first old lock with the same owner as the new lock */
list_for_each_entry(fl, &ctx->flc_posix, c.flc_list) {
if (posix_same_owner(&request->c, &fl->c))
break;
}
/* Process locks with this owner. */
list_for_each_entry_safe_from(fl, tmp, &ctx->flc_posix, c.flc_list) {
if (!posix_same_owner(&request->c, &fl->c))
break;
/* Detect adjacent or overlapping regions (if same lock type) */
if (request->c.flc_type == fl->c.flc_type) {
/* In all comparisons of start vs end, use
* "start - 1" rather than "end + 1". If end
* is OFFSET_MAX, end + 1 will become negative.
*/
if (fl->fl_end < request->fl_start - 1)
continue;
/* If the next lock in the list has entirely bigger
* addresses than the new one, insert the lock here.
*/
if (fl->fl_start - 1 > request->fl_end)
break;
/* If we come here, the new and old lock are of the
* same type and adjacent or overlapping. Make one
* lock yielding from the lower start address of both
* locks to the higher end address.
*/
if (fl->fl_start > request->fl_start)
fl->fl_start = request->fl_start;
else
request->fl_start = fl->fl_start;
if (fl->fl_end < request->fl_end)
fl->fl_end = request->fl_end;
else
request->fl_end = fl->fl_end;
if (added) {
locks_delete_lock_ctx(&fl->c, &dispose);
continue;
}
request = fl;
added = true;
} else {
/* Processing for different lock types is a bit
* more complex.
*/
if (fl->fl_end < request->fl_start)
continue;
if (fl->fl_start > request->fl_end)
break;
if (lock_is_unlock(request))
added = true;
if (fl->fl_start < request->fl_start)
left = fl;
/* If the next lock in the list has a higher end
* address than the new one, insert the new one here.
*/
if (fl->fl_end > request->fl_end) {
right = fl;
break;
}
if (fl->fl_start >= request->fl_start) {
/* The new lock completely replaces an old
* one (This may happen several times).
*/
if (added) {
locks_delete_lock_ctx(&fl->c, &dispose);
continue;
}
/*
* Replace the old lock with new_fl, and
* remove the old one. It's safe to do the
* insert here since we know that we won't be
* using new_fl later, and that the lock is
* just replacing an existing lock.
*/
error = -ENOLCK;
if (!new_fl)
goto out;
locks_copy_lock(new_fl, request);
locks_move_blocks(new_fl, request);
request = new_fl;
new_fl = NULL;
locks_insert_lock_ctx(&request->c,
&fl->c.flc_list);
locks_delete_lock_ctx(&fl->c, &dispose);
added = true;
}
}
}
/*
* The above code only modifies existing locks in case of merging or
* replacing. If new lock(s) need to be inserted all modifications are
* done below this, so it's safe yet to bail out.
*/
error = -ENOLCK; /* "no luck" */
if (right && left == right && !new_fl2)
goto out;
error = 0;
if (!added) {
if (lock_is_unlock(request)) {
if (request->c.flc_flags & FL_EXISTS)
error = -ENOENT;
goto out;
}
if (!new_fl) {
error = -ENOLCK;
goto out;
}
locks_copy_lock(new_fl, request);
locks_move_blocks(new_fl, request);
locks_insert_lock_ctx(&new_fl->c, &fl->c.flc_list);
fl = new_fl;
new_fl = NULL;
}
if (right) {
if (left == right) {
/* The new lock breaks the old one in two pieces,
* so we have to use the second new lock.
*/
left = new_fl2;
new_fl2 = NULL;
locks_copy_lock(left, right);
locks_insert_lock_ctx(&left->c, &fl->c.flc_list);
}
right->fl_start = request->fl_end + 1;
locks_wake_up_blocks(&right->c);
}
if (left) {
left->fl_end = request->fl_start - 1;
locks_wake_up_blocks(&left->c);
}
out:
trace_posix_lock_inode(inode, request, error);
spin_unlock(&ctx->flc_lock);
percpu_up_read(&file_rwsem);
/*
* Free any unused locks.
*/
if (new_fl)
locks_free_lock(new_fl);
if (new_fl2)
locks_free_lock(new_fl2);
locks_dispose_list(&dispose);
return error;
}
/**
* posix_lock_file - Apply a POSIX-style lock to a file
* @filp: The file to apply the lock to
* @fl: The lock to be applied
* @conflock: Place to return a copy of the conflicting lock, if found.
*
* Add a POSIX style lock to a file.
* We merge adjacent & overlapping locks whenever possible.
* POSIX locks are sorted by owner task, then by starting address
*
* Note that if called with an FL_EXISTS argument, the caller may determine
* whether or not a lock was successfully freed by testing the return
* value for -ENOENT.
*/
int posix_lock_file(struct file *filp, struct file_lock *fl,
struct file_lock *conflock)
{
return posix_lock_inode(file_inode(filp), fl, conflock);
}
EXPORT_SYMBOL(posix_lock_file);
/**
* posix_lock_inode_wait - Apply a POSIX-style lock to a file
* @inode: inode of file to which lock request should be applied
* @fl: The lock to be applied
*
* Apply a POSIX style lock request to an inode.
*/
static int posix_lock_inode_wait(struct inode *inode, struct file_lock *fl)
{
int error;
might_sleep ();
for (;;) {
error = posix_lock_inode(inode, fl, NULL);
if (error != FILE_LOCK_DEFERRED)
break;
error = wait_event_interruptible(fl->c.flc_wait,
list_empty(&fl->c.flc_blocked_member));
if (error)
break;
}
locks_delete_block(fl);
return error;
}
static void lease_clear_pending(struct file_lease *fl, int arg)
{
switch (arg) {
case F_UNLCK:
fl->c.flc_flags &= ~FL_UNLOCK_PENDING;
fallthrough;
case F_RDLCK:
fl->c.flc_flags &= ~FL_DOWNGRADE_PENDING;
}
}
/* We already had a lease on this file; just change its type */
int lease_modify(struct file_lease *fl, int arg, struct list_head *dispose)
{
int error = assign_type(&fl->c, arg);
if (error)
return error;
lease_clear_pending(fl, arg);
locks_wake_up_blocks(&fl->c);
if (arg == F_UNLCK) {
struct file *filp = fl->c.flc_file;
f_delown(filp);
file_f_owner(filp)->signum = 0;
fasync_helper(0, fl->c.flc_file, 0, &fl->fl_fasync);
if (fl->fl_fasync != NULL) {
printk(KERN_ERR "locks_delete_lock: fasync == %p\n", fl->fl_fasync);
fl->fl_fasync = NULL;
}
locks_delete_lock_ctx(&fl->c, dispose);
}
return 0;
}
EXPORT_SYMBOL(lease_modify);
static bool past_time(unsigned long then)
{
if (!then)
/* 0 is a special value meaning "this never expires": */
return false;
return time_after(jiffies, then);
}
static void time_out_leases(struct inode *inode, struct list_head *dispose)
{
struct file_lock_context *ctx = inode->i_flctx;
struct file_lease *fl, *tmp;
lockdep_assert_held(&ctx->flc_lock);
list_for_each_entry_safe(fl, tmp, &ctx->flc_lease, c.flc_list) {
trace_time_out_leases(inode, fl);
if (past_time(fl->fl_downgrade_time))
lease_modify(fl, F_RDLCK, dispose);
if (past_time(fl->fl_break_time))
lease_modify(fl, F_UNLCK, dispose);
}
}
static bool leases_conflict(struct file_lock_core *lc, struct file_lock_core *bc)
{
bool rc;
struct file_lease *lease = file_lease(lc);
struct file_lease *breaker = file_lease(bc);
if (lease->fl_lmops->lm_breaker_owns_lease
&& lease->fl_lmops->lm_breaker_owns_lease(lease))
return false;
if ((bc->flc_flags & FL_LAYOUT) != (lc->flc_flags & FL_LAYOUT)) {
rc = false;
goto trace;
}
if ((bc->flc_flags & FL_DELEG) && (lc->flc_flags & FL_LEASE)) {
rc = false;
goto trace;
}
rc = locks_conflict(bc, lc);
trace:
trace_leases_conflict(rc, lease, breaker);
return rc;
}
static bool
any_leases_conflict(struct inode *inode, struct file_lease *breaker)
{
struct file_lock_context *ctx = inode->i_flctx;
struct file_lock_core *flc;
lockdep_assert_held(&ctx->flc_lock);
list_for_each_entry(flc, &ctx->flc_lease, flc_list) {
if (leases_conflict(flc, &breaker->c))
return true;
}
return false;
}
/**
* __break_lease - revoke all outstanding leases on file
* @inode: the inode of the file to return
* @mode: O_RDONLY: break only write leases; O_WRONLY or O_RDWR:
* break all leases
* @type: FL_LEASE: break leases and delegations; FL_DELEG: break
* only delegations
*
* break_lease (inlined for speed) has checked there already is at least
* some kind of lock (maybe a lease) on this file. Leases are broken on
* a call to open() or truncate(). This function can sleep unless you
* specified %O_NONBLOCK to your open().
*/
int __break_lease(struct inode *inode, unsigned int mode, unsigned int type)
{
int error = 0;
struct file_lock_context *ctx;
struct file_lease *new_fl, *fl, *tmp;
unsigned long break_time;
int want_write = (mode & O_ACCMODE) != O_RDONLY;
LIST_HEAD(dispose);
new_fl = lease_alloc(NULL, want_write ? F_WRLCK : F_RDLCK);
if (IS_ERR(new_fl))
return PTR_ERR(new_fl);
new_fl->c.flc_flags = type;
/* typically we will check that ctx is non-NULL before calling */
ctx = locks_inode_context(inode);
if (!ctx) {
WARN_ON_ONCE(1);
goto free_lock;
}
percpu_down_read(&file_rwsem);
spin_lock(&ctx->flc_lock);
time_out_leases(inode, &dispose);
if (!any_leases_conflict(inode, new_fl))
goto out;
break_time = 0;
if (lease_break_time > 0) {
break_time = jiffies + lease_break_time * HZ;
if (break_time == 0)
break_time++; /* so that 0 means no break time */
}
list_for_each_entry_safe(fl, tmp, &ctx->flc_lease, c.flc_list) {
if (!leases_conflict(&fl->c, &new_fl->c))
continue;
if (want_write) {
if (fl->c.flc_flags & FL_UNLOCK_PENDING)
continue;
fl->c.flc_flags |= FL_UNLOCK_PENDING;
fl->fl_break_time = break_time;
} else {
if (lease_breaking(fl))
continue;
fl->c.flc_flags |= FL_DOWNGRADE_PENDING;
fl->fl_downgrade_time = break_time;
}
if (fl->fl_lmops->lm_break(fl))
locks_delete_lock_ctx(&fl->c, &dispose);
}
if (list_empty(&ctx->flc_lease))
goto out;
if (mode & O_NONBLOCK) {
trace_break_lease_noblock(inode, new_fl);
error = -EWOULDBLOCK;
goto out;
}
restart:
fl = list_first_entry(&ctx->flc_lease, struct file_lease, c.flc_list);
break_time = fl->fl_break_time;
if (break_time != 0)
break_time -= jiffies;
if (break_time == 0)
break_time++;
locks_insert_block(&fl->c, &new_fl->c, leases_conflict);
trace_break_lease_block(inode, new_fl);
spin_unlock(&ctx->flc_lock);
percpu_up_read(&file_rwsem);
locks_dispose_list(&dispose);
error = wait_event_interruptible_timeout(new_fl->c.flc_wait,
list_empty(&new_fl->c.flc_blocked_member),
break_time);
percpu_down_read(&file_rwsem);
spin_lock(&ctx->flc_lock);
trace_break_lease_unblock(inode, new_fl);
__locks_delete_block(&new_fl->c);
if (error >= 0) {
/*
* Wait for the next conflicting lease that has not been
* broken yet
*/
if (error == 0)
time_out_leases(inode, &dispose);
if (any_leases_conflict(inode, new_fl))
goto restart;
error = 0;
}
out:
spin_unlock(&ctx->flc_lock);
percpu_up_read(&file_rwsem);
locks_dispose_list(&dispose);
free_lock:
locks_free_lease(new_fl);
return error;
}
EXPORT_SYMBOL(__break_lease);
/**
* lease_get_mtime - update modified time of an inode with exclusive lease
* @inode: the inode
* @time: pointer to a timespec which contains the last modified time
*
* This is to force NFS clients to flush their caches for files with
* exclusive leases. The justification is that if someone has an
* exclusive lease, then they could be modifying it.
*/
void lease_get_mtime(struct inode *inode, struct timespec64 *time)
{
bool has_lease = false;
struct file_lock_context *ctx;
struct file_lock_core *flc;
ctx = locks_inode_context(inode);
if (ctx && !list_empty_careful(&ctx->flc_lease)) {
spin_lock(&ctx->flc_lock);
flc = list_first_entry_or_null(&ctx->flc_lease,
struct file_lock_core, flc_list);
if (flc && flc->flc_type == F_WRLCK)
has_lease = true;
spin_unlock(&ctx->flc_lock);
}
if (has_lease)
*time = current_time(inode);
}
EXPORT_SYMBOL(lease_get_mtime);
/**
* fcntl_getlease - Enquire what lease is currently active
* @filp: the file
*
* The value returned by this function will be one of
* (if no lease break is pending):
*
* %F_RDLCK to indicate a shared lease is held.
*
* %F_WRLCK to indicate an exclusive lease is held.
*
* %F_UNLCK to indicate no lease is held.
*
* (if a lease break is pending):
*
* %F_RDLCK to indicate an exclusive lease needs to be
* changed to a shared lease (or removed).
*
* %F_UNLCK to indicate the lease needs to be removed.
*
* XXX: sfr & willy disagree over whether F_INPROGRESS
* should be returned to userspace.
*/
int fcntl_getlease(struct file *filp)
{
struct file_lease *fl;
struct inode *inode = file_inode(filp);
struct file_lock_context *ctx;
int type = F_UNLCK;
LIST_HEAD(dispose);
ctx = locks_inode_context(inode);
if (ctx && !list_empty_careful(&ctx->flc_lease)) {
percpu_down_read(&file_rwsem);
spin_lock(&ctx->flc_lock);
time_out_leases(inode, &dispose);
list_for_each_entry(fl, &ctx->flc_lease, c.flc_list) {
if (fl->c.flc_file != filp)
continue;
type = target_leasetype(fl);
break;
}
spin_unlock(&ctx->flc_lock);
percpu_up_read(&file_rwsem);
locks_dispose_list(&dispose);
}
return type;
}
/**
* check_conflicting_open - see if the given file points to an inode that has
* an existing open that would conflict with the
* desired lease.
* @filp: file to check
* @arg: type of lease that we're trying to acquire
* @flags: current lock flags
*
* Check to see if there's an existing open fd on this file that would
* conflict with the lease we're trying to set.
*/
static int
check_conflicting_open(struct file *filp, const int arg, int flags)
{
struct inode *inode = file_inode(filp);
int self_wcount = 0, self_rcount = 0;
if (flags & FL_LAYOUT)
return 0;
if (flags & FL_DELEG)
/* We leave these checks to the caller */
return 0;
if (arg == F_RDLCK)
return inode_is_open_for_write(inode) ? -EAGAIN : 0;
else if (arg != F_WRLCK)
return 0;
/*
* Make sure that only read/write count is from lease requestor.
* Note that this will result in denying write leases when i_writecount
* is negative, which is what we want. (We shouldn't grant write leases
* on files open for execution.)
*/
if (filp->f_mode & FMODE_WRITE)
self_wcount = 1;
else if (filp->f_mode & FMODE_READ)
self_rcount = 1;
if (atomic_read(&inode->i_writecount) != self_wcount ||
atomic_read(&inode->i_readcount) != self_rcount)
return -EAGAIN;
return 0;
}
static int
generic_add_lease(struct file *filp, int arg, struct file_lease **flp, void **priv)
{
struct file_lease *fl, *my_fl = NULL, *lease;
struct inode *inode = file_inode(filp);
struct file_lock_context *ctx;
bool is_deleg = (*flp)->c.flc_flags & FL_DELEG;
int error;
LIST_HEAD(dispose);
lease = *flp;
trace_generic_add_lease(inode, lease);
error = file_f_owner_allocate(filp);
if (error)
return error;
/* Note that arg is never F_UNLCK here */
ctx = locks_get_lock_context(inode, arg);
if (!ctx)
return -ENOMEM;
/*
* In the delegation case we need mutual exclusion with
* a number of operations that take the i_mutex. We trylock
* because delegations are an optional optimization, and if
* there's some chance of a conflict--we'd rather not
* bother, maybe that's a sign this just isn't a good file to
* hand out a delegation on.
*/
if (is_deleg && !inode_trylock(inode))
return -EAGAIN;
percpu_down_read(&file_rwsem);
spin_lock(&ctx->flc_lock);
time_out_leases(inode, &dispose);
error = check_conflicting_open(filp, arg, lease->c.flc_flags);
if (error)
goto out;
/*
* At this point, we know that if there is an exclusive
* lease on this file, then we hold it on this filp
* (otherwise our open of this file would have blocked).
* And if we are trying to acquire an exclusive lease,
* then the file is not open by anyone (including us)
* except for this filp.
*/
error = -EAGAIN;
list_for_each_entry(fl, &ctx->flc_lease, c.flc_list) {
if (fl->c.flc_file == filp &&
fl->c.flc_owner == lease->c.flc_owner) {
my_fl = fl;
continue;
}
/*
* No exclusive leases if someone else has a lease on
* this file:
*/
if (arg == F_WRLCK)
goto out;
/*
* Modifying our existing lease is OK, but no getting a
* new lease if someone else is opening for write:
*/
if (fl->c.flc_flags & FL_UNLOCK_PENDING)
goto out;
}
if (my_fl != NULL) {
lease = my_fl;
error = lease->fl_lmops->lm_change(lease, arg, &dispose);
if (error)
goto out;
goto out_setup;
}
error = -EINVAL;
if (!leases_enable)
goto out;
locks_insert_lock_ctx(&lease->c, &ctx->flc_lease);
/*
* The check in break_lease() is lockless. It's possible for another
* open to race in after we did the earlier check for a conflicting
* open but before the lease was inserted. Check again for a
* conflicting open and cancel the lease if there is one.
*
* We also add a barrier here to ensure that the insertion of the lock
* precedes these checks.
*/
smp_mb();
error = check_conflicting_open(filp, arg, lease->c.flc_flags);
if (error) {
locks_unlink_lock_ctx(&lease->c);
goto out;
}
out_setup:
if (lease->fl_lmops->lm_setup)
lease->fl_lmops->lm_setup(lease, priv);
out:
spin_unlock(&ctx->flc_lock);
percpu_up_read(&file_rwsem);
locks_dispose_list(&dispose);
if (is_deleg)
inode_unlock(inode);
if (!error && !my_fl)
*flp = NULL;
return error;
}
static int generic_delete_lease(struct file *filp, void *owner)
{
int error = -EAGAIN;
struct file_lease *fl, *victim = NULL;
struct inode *inode = file_inode(filp);
struct file_lock_context *ctx;
LIST_HEAD(dispose);
ctx = locks_inode_context(inode);
if (!ctx) {
trace_generic_delete_lease(inode, NULL);
return error;
}
percpu_down_read(&file_rwsem);
spin_lock(&ctx->flc_lock);
list_for_each_entry(fl, &ctx->flc_lease, c.flc_list) {
if (fl->c.flc_file == filp &&
fl->c.flc_owner == owner) {
victim = fl;
break;
}
}
trace_generic_delete_lease(inode, victim);
if (victim)
error = fl->fl_lmops->lm_change(victim, F_UNLCK, &dispose);
spin_unlock(&ctx->flc_lock);
percpu_up_read(&file_rwsem);
locks_dispose_list(&dispose);
return error;
}
/**
* generic_setlease - sets a lease on an open file
* @filp: file pointer
* @arg: type of lease to obtain
* @flp: input - file_lock to use, output - file_lock inserted
* @priv: private data for lm_setup (may be NULL if lm_setup
* doesn't require it)
*
* The (input) flp->fl_lmops->lm_break function is required
* by break_lease().
*/
int generic_setlease(struct file *filp, int arg, struct file_lease **flp,
void **priv)
{
switch (arg) {
case F_UNLCK:
return generic_delete_lease(filp, *priv);
case F_RDLCK:
case F_WRLCK:
if (!(*flp)->fl_lmops->lm_break) {
WARN_ON_ONCE(1);
return -ENOLCK;
}
return generic_add_lease(filp, arg, flp, priv);
default:
return -EINVAL;
}
}
EXPORT_SYMBOL(generic_setlease);
/*
* Kernel subsystems can register to be notified on any attempt to set
* a new lease with the lease_notifier_chain. This is used by (e.g.) nfsd
* to close files that it may have cached when there is an attempt to set a
* conflicting lease.
*/
static struct srcu_notifier_head lease_notifier_chain;
static inline void
lease_notifier_chain_init(void)
{
srcu_init_notifier_head(&lease_notifier_chain);
}
static inline void
setlease_notifier(int arg, struct file_lease *lease)
{
if (arg != F_UNLCK)
srcu_notifier_call_chain(&lease_notifier_chain, arg, lease);
}
int lease_register_notifier(struct notifier_block *nb)
{
return srcu_notifier_chain_register(&lease_notifier_chain, nb);
}
EXPORT_SYMBOL_GPL(lease_register_notifier);
void lease_unregister_notifier(struct notifier_block *nb)
{
srcu_notifier_chain_unregister(&lease_notifier_chain, nb);
}
EXPORT_SYMBOL_GPL(lease_unregister_notifier);
int
kernel_setlease(struct file *filp, int arg, struct file_lease **lease, void **priv)
{
if (lease)
setlease_notifier(arg, *lease);
if (filp->f_op->setlease)
return filp->f_op->setlease(filp, arg, lease, priv);
else
return generic_setlease(filp, arg, lease, priv);
}
EXPORT_SYMBOL_GPL(kernel_setlease);
/**
* vfs_setlease - sets a lease on an open file
* @filp: file pointer
* @arg: type of lease to obtain
* @lease: file_lock to use when adding a lease
* @priv: private info for lm_setup when adding a lease (may be
* NULL if lm_setup doesn't require it)
*
* Call this to establish a lease on the file. The "lease" argument is not
* used for F_UNLCK requests and may be NULL. For commands that set or alter
* an existing lease, the ``(*lease)->fl_lmops->lm_break`` operation must be
* set; if not, this function will return -ENOLCK (and generate a scary-looking
* stack trace).
*
* The "priv" pointer is passed directly to the lm_setup function as-is. It
* may be NULL if the lm_setup operation doesn't require it.
*/
int
vfs_setlease(struct file *filp, int arg, struct file_lease **lease, void **priv)
{
struct inode *inode = file_inode(filp);
vfsuid_t vfsuid = i_uid_into_vfsuid(file_mnt_idmap(filp), inode);
int error;
if ((!vfsuid_eq_kuid(vfsuid, current_fsuid())) && !capable(CAP_LEASE))
return -EACCES;
if (!S_ISREG(inode->i_mode))
return -EINVAL;
error = security_file_lock(filp, arg);
if (error)
return error;
return kernel_setlease(filp, arg, lease, priv);
}
EXPORT_SYMBOL_GPL(vfs_setlease);
static int do_fcntl_add_lease(unsigned int fd, struct file *filp, int arg)
{
struct file_lease *fl;
struct fasync_struct *new;
int error;
fl = lease_alloc(filp, arg);
if (IS_ERR(fl))
return PTR_ERR(fl);
new = fasync_alloc();
if (!new) {
locks_free_lease(fl);
return -ENOMEM;
}
new->fa_fd = fd;
error = vfs_setlease(filp, arg, &fl, (void **)&new);
if (fl)
locks_free_lease(fl);
if (new)
fasync_free(new);
return error;
}
/**
* fcntl_setlease - sets a lease on an open file
* @fd: open file descriptor
* @filp: file pointer
* @arg: type of lease to obtain
*
* Call this fcntl to establish a lease on the file.
* Note that you also need to call %F_SETSIG to
* receive a signal when the lease is broken.
*/
int fcntl_setlease(unsigned int fd, struct file *filp, int arg)
{
if (arg == F_UNLCK)
return vfs_setlease(filp, F_UNLCK, NULL, (void **)&filp);
return do_fcntl_add_lease(fd, filp, arg);
}
/**
* flock_lock_inode_wait - Apply a FLOCK-style lock to a file
* @inode: inode of the file to apply to
* @fl: The lock to be applied
*
* Apply a FLOCK style lock request to an inode.
*/
static int flock_lock_inode_wait(struct inode *inode, struct file_lock *fl)
{
int error;
might_sleep();
for (;;) {
error = flock_lock_inode(inode, fl);
if (error != FILE_LOCK_DEFERRED)
break;
error = wait_event_interruptible(fl->c.flc_wait,
list_empty(&fl->c.flc_blocked_member));
if (error)
break;
}
locks_delete_block(fl);
return error;
}
/**
* locks_lock_inode_wait - Apply a lock to an inode
* @inode: inode of the file to apply to
* @fl: The lock to be applied
*
* Apply a POSIX or FLOCK style lock request to an inode.
*/
int locks_lock_inode_wait(struct inode *inode, struct file_lock *fl)
{
int res = 0;
switch (fl->c.flc_flags & (FL_POSIX|FL_FLOCK)) {
case FL_POSIX:
res = posix_lock_inode_wait(inode, fl);
break;
case FL_FLOCK:
res = flock_lock_inode_wait(inode, fl);
break;
default:
BUG();
}
return res;
}
EXPORT_SYMBOL(locks_lock_inode_wait);
/**
* sys_flock: - flock() system call.
* @fd: the file descriptor to lock.
* @cmd: the type of lock to apply.
*
* Apply a %FL_FLOCK style lock to an open file descriptor.
* The @cmd can be one of:
*
* - %LOCK_SH -- a shared lock.
* - %LOCK_EX -- an exclusive lock.
* - %LOCK_UN -- remove an existing lock.
* - %LOCK_MAND -- a 'mandatory' flock. (DEPRECATED)
*
* %LOCK_MAND support has been removed from the kernel.
*/
SYSCALL_DEFINE2(flock, unsigned int, fd, unsigned int, cmd)
{
int can_sleep, error, type;
struct file_lock fl;
struct fd f;
/*
* LOCK_MAND locks were broken for a long time in that they never
* conflicted with one another and didn't prevent any sort of open,
* read or write activity.
*
* Just ignore these requests now, to preserve legacy behavior, but
* throw a warning to let people know that they don't actually work.
*/
if (cmd & LOCK_MAND) {
pr_warn_once("%s(%d): Attempt to set a LOCK_MAND lock via flock(2). This support has been removed and the request ignored.\n", current->comm, current->pid);
return 0;
}
type = flock_translate_cmd(cmd & ~LOCK_NB);
if (type < 0)
return type;
error = -EBADF;
f = fdget(fd);
if (!fd_file(f))
return error;
if (type != F_UNLCK && !(fd_file(f)->f_mode & (FMODE_READ | FMODE_WRITE)))
goto out_putf;
flock_make_lock(fd_file(f), &fl, type);
error = security_file_lock(fd_file(f), fl.c.flc_type);
if (error)
goto out_putf;
can_sleep = !(cmd & LOCK_NB);
if (can_sleep)
fl.c.flc_flags |= FL_SLEEP;
if (fd_file(f)->f_op->flock)
error = fd_file(f)->f_op->flock(fd_file(f),
(can_sleep) ? F_SETLKW : F_SETLK,
&fl);
else
error = locks_lock_file_wait(fd_file(f), &fl);
locks_release_private(&fl);
out_putf:
fdput(f);
return error;
}
/**
* vfs_test_lock - test file byte range lock
* @filp: The file to test lock for
* @fl: The lock to test; also used to hold result
*
* Returns -ERRNO on failure. Indicates presence of conflicting lock by
* setting conf->fl_type to something other than F_UNLCK.
*/
int vfs_test_lock(struct file *filp, struct file_lock *fl)
{
WARN_ON_ONCE(filp != fl->c.flc_file);
if (filp->f_op->lock)
return filp->f_op->lock(filp, F_GETLK, fl);
posix_test_lock(filp, fl);
return 0;
}
EXPORT_SYMBOL_GPL(vfs_test_lock);
/**
* locks_translate_pid - translate a file_lock's fl_pid number into a namespace
* @fl: The file_lock who's fl_pid should be translated
* @ns: The namespace into which the pid should be translated
*
* Used to translate a fl_pid into a namespace virtual pid number
*/
static pid_t locks_translate_pid(struct file_lock_core *fl, struct pid_namespace *ns)
{
pid_t vnr;
struct pid *pid;
if (fl->flc_flags & FL_OFDLCK)
return -1;
/* Remote locks report a negative pid value */
if (fl->flc_pid <= 0)
return fl->flc_pid;
/*
* If the flock owner process is dead and its pid has been already
* freed, the translation below won't work, but we still want to show
* flock owner pid number in init pidns.
*/
if (ns == &init_pid_ns)
return (pid_t) fl->flc_pid;
rcu_read_lock();
pid = find_pid_ns(fl->flc_pid, &init_pid_ns);
vnr = pid_nr_ns(pid, ns);
rcu_read_unlock();
return vnr;
}
static int posix_lock_to_flock(struct flock *flock, struct file_lock *fl)
{
flock->l_pid = locks_translate_pid(&fl->c, task_active_pid_ns(current));
#if BITS_PER_LONG == 32
/*
* Make sure we can represent the posix lock via
* legacy 32bit flock.
*/
if (fl->fl_start > OFFT_OFFSET_MAX)
return -EOVERFLOW;
if (fl->fl_end != OFFSET_MAX && fl->fl_end > OFFT_OFFSET_MAX)
return -EOVERFLOW;
#endif
flock->l_start = fl->fl_start;
flock->l_len = fl->fl_end == OFFSET_MAX ? 0 :
fl->fl_end - fl->fl_start + 1;
flock->l_whence = 0;
flock->l_type = fl->c.flc_type;
return 0;
}
#if BITS_PER_LONG == 32
static void posix_lock_to_flock64(struct flock64 *flock, struct file_lock *fl)
{
flock->l_pid = locks_translate_pid(&fl->c, task_active_pid_ns(current));
flock->l_start = fl->fl_start;
flock->l_len = fl->fl_end == OFFSET_MAX ? 0 :
fl->fl_end - fl->fl_start + 1;
flock->l_whence = 0;
flock->l_type = fl->c.flc_type;
}
#endif
/* Report the first existing lock that would conflict with l.
* This implements the F_GETLK command of fcntl().
*/
int fcntl_getlk(struct file *filp, unsigned int cmd, struct flock *flock)
{
struct file_lock *fl;
int error;
fl = locks_alloc_lock();
if (fl == NULL)
return -ENOMEM;
error = -EINVAL;
if (cmd != F_OFD_GETLK && flock->l_type != F_RDLCK
&& flock->l_type != F_WRLCK)
goto out;
error = flock_to_posix_lock(filp, fl, flock);
if (error)
goto out;
if (cmd == F_OFD_GETLK) {
error = -EINVAL;
if (flock->l_pid != 0)
goto out;
fl->c.flc_flags |= FL_OFDLCK;
fl->c.flc_owner = filp;
}
error = vfs_test_lock(filp, fl);
if (error)
goto out;
flock->l_type = fl->c.flc_type;
if (fl->c.flc_type != F_UNLCK) {
error = posix_lock_to_flock(flock, fl);
if (error)
goto out;
}
out:
locks_free_lock(fl);
return error;
}
/**
* vfs_lock_file - file byte range lock
* @filp: The file to apply the lock to
* @cmd: type of locking operation (F_SETLK, F_GETLK, etc.)
* @fl: The lock to be applied
* @conf: Place to return a copy of the conflicting lock, if found.
*
* A caller that doesn't care about the conflicting lock may pass NULL
* as the final argument.
*
* If the filesystem defines a private ->lock() method, then @conf will
* be left unchanged; so a caller that cares should initialize it to
* some acceptable default.
*
* To avoid blocking kernel daemons, such as lockd, that need to acquire POSIX
* locks, the ->lock() interface may return asynchronously, before the lock has
* been granted or denied by the underlying filesystem, if (and only if)
* lm_grant is set. Additionally EXPORT_OP_ASYNC_LOCK in export_operations
* flags need to be set.
*
* Callers expecting ->lock() to return asynchronously will only use F_SETLK,
* not F_SETLKW; they will set FL_SLEEP if (and only if) the request is for a
* blocking lock. When ->lock() does return asynchronously, it must return
* FILE_LOCK_DEFERRED, and call ->lm_grant() when the lock request completes.
* If the request is for non-blocking lock the file system should return
* FILE_LOCK_DEFERRED then try to get the lock and call the callback routine
* with the result. If the request timed out the callback routine will return a
* nonzero return code and the file system should release the lock. The file
* system is also responsible to keep a corresponding posix lock when it
* grants a lock so the VFS can find out which locks are locally held and do
* the correct lock cleanup when required.
* The underlying filesystem must not drop the kernel lock or call
* ->lm_grant() before returning to the caller with a FILE_LOCK_DEFERRED
* return code.
*/
int vfs_lock_file(struct file *filp, unsigned int cmd, struct file_lock *fl, struct file_lock *conf)
{
WARN_ON_ONCE(filp != fl->c.flc_file);
if (filp->f_op->lock)
return filp->f_op->lock(filp, cmd, fl);
else
return posix_lock_file(filp, fl, conf);
}
EXPORT_SYMBOL_GPL(vfs_lock_file);
static int do_lock_file_wait(struct file *filp, unsigned int cmd,
struct file_lock *fl)
{
int error;
error = security_file_lock(filp, fl->c.flc_type);
if (error)
return error;
for (;;) {
error = vfs_lock_file(filp, cmd, fl, NULL);
if (error != FILE_LOCK_DEFERRED)
break;
error = wait_event_interruptible(fl->c.flc_wait,
list_empty(&fl->c.flc_blocked_member));
if (error)
break;
}
locks_delete_block(fl);
return error;
}
/* Ensure that fl->fl_file has compatible f_mode for F_SETLK calls */
static int
check_fmode_for_setlk(struct file_lock *fl)
{
switch (fl->c.flc_type) {
case F_RDLCK:
if (!(fl->c.flc_file->f_mode & FMODE_READ))
return -EBADF;
break;
case F_WRLCK:
if (!(fl->c.flc_file->f_mode & FMODE_WRITE))
return -EBADF;
}
return 0;
}
/* Apply the lock described by l to an open file descriptor.
* This implements both the F_SETLK and F_SETLKW commands of fcntl().
*/
int fcntl_setlk(unsigned int fd, struct file *filp, unsigned int cmd,
struct flock *flock)
{
struct file_lock *file_lock = locks_alloc_lock();
struct inode *inode = file_inode(filp);
struct file *f;
int error;
if (file_lock == NULL)
return -ENOLCK;
error = flock_to_posix_lock(filp, file_lock, flock);
if (error)
goto out;
error = check_fmode_for_setlk(file_lock);
if (error)
goto out;
/*
* If the cmd is requesting file-private locks, then set the
* FL_OFDLCK flag and override the owner.
*/
switch (cmd) {
case F_OFD_SETLK:
error = -EINVAL;
if (flock->l_pid != 0)
goto out;
cmd = F_SETLK;
file_lock->c.flc_flags |= FL_OFDLCK;
file_lock->c.flc_owner = filp;
break;
case F_OFD_SETLKW:
error = -EINVAL;
if (flock->l_pid != 0)
goto out;
cmd = F_SETLKW;
file_lock->c.flc_flags |= FL_OFDLCK;
file_lock->c.flc_owner = filp;
fallthrough;
case F_SETLKW:
file_lock->c.flc_flags |= FL_SLEEP;
}
error = do_lock_file_wait(filp, cmd, file_lock);
/*
* Detect close/fcntl races and recover by zapping all POSIX locks
* associated with this file and our files_struct, just like on
* filp_flush(). There is no need to do that when we're
* unlocking though, or for OFD locks.
*/
if (!error && file_lock->c.flc_type != F_UNLCK &&
!(file_lock->c.flc_flags & FL_OFDLCK)) {
struct files_struct *files = current->files;
/*
* We need that spin_lock here - it prevents reordering between
* update of i_flctx->flc_posix and check for it done in
* close(). rcu_read_lock() wouldn't do.
*/
spin_lock(&files->file_lock);
f = files_lookup_fd_locked(files, fd);
spin_unlock(&files->file_lock);
if (f != filp) {
locks_remove_posix(filp, files);
error = -EBADF;
}
}
out:
trace_fcntl_setlk(inode, file_lock, error);
locks_free_lock(file_lock);
return error;
}
#if BITS_PER_LONG == 32
/* Report the first existing lock that would conflict with l.
* This implements the F_GETLK command of fcntl().
*/
int fcntl_getlk64(struct file *filp, unsigned int cmd, struct flock64 *flock)
{
struct file_lock *fl;
int error;
fl = locks_alloc_lock();
if (fl == NULL)
return -ENOMEM;
error = -EINVAL;
if (cmd != F_OFD_GETLK && flock->l_type != F_RDLCK
&& flock->l_type != F_WRLCK)
goto out;
error = flock64_to_posix_lock(filp, fl, flock);
if (error)
goto out;
if (cmd == F_OFD_GETLK) {
error = -EINVAL;
if (flock->l_pid != 0)
goto out;
fl->c.flc_flags |= FL_OFDLCK;
fl->c.flc_owner = filp;
}
error = vfs_test_lock(filp, fl);
if (error)
goto out;
flock->l_type = fl->c.flc_type;
if (fl->c.flc_type != F_UNLCK)
posix_lock_to_flock64(flock, fl);
out:
locks_free_lock(fl);
return error;
}
/* Apply the lock described by l to an open file descriptor.
* This implements both the F_SETLK and F_SETLKW commands of fcntl().
*/
int fcntl_setlk64(unsigned int fd, struct file *filp, unsigned int cmd,
struct flock64 *flock)
{
struct file_lock *file_lock = locks_alloc_lock();
struct file *f;
int error;
if (file_lock == NULL)
return -ENOLCK;
error = flock64_to_posix_lock(filp, file_lock, flock);
if (error)
goto out;
error = check_fmode_for_setlk(file_lock);
if (error)
goto out;
/*
* If the cmd is requesting file-private locks, then set the
* FL_OFDLCK flag and override the owner.
*/
switch (cmd) {
case F_OFD_SETLK:
error = -EINVAL;
if (flock->l_pid != 0)
goto out;
cmd = F_SETLK64;
file_lock->c.flc_flags |= FL_OFDLCK;
file_lock->c.flc_owner = filp;
break;
case F_OFD_SETLKW:
error = -EINVAL;
if (flock->l_pid != 0)
goto out;
cmd = F_SETLKW64;
file_lock->c.flc_flags |= FL_OFDLCK;
file_lock->c.flc_owner = filp;
fallthrough;
case F_SETLKW64:
file_lock->c.flc_flags |= FL_SLEEP;
}
error = do_lock_file_wait(filp, cmd, file_lock);
/*
* Detect close/fcntl races and recover by zapping all POSIX locks
* associated with this file and our files_struct, just like on
* filp_flush(). There is no need to do that when we're
* unlocking though, or for OFD locks.
*/
if (!error && file_lock->c.flc_type != F_UNLCK &&
!(file_lock->c.flc_flags & FL_OFDLCK)) {
struct files_struct *files = current->files;
/*
* We need that spin_lock here - it prevents reordering between
* update of i_flctx->flc_posix and check for it done in
* close(). rcu_read_lock() wouldn't do.
*/
spin_lock(&files->file_lock);
f = files_lookup_fd_locked(files, fd);
spin_unlock(&files->file_lock);
if (f != filp) {
locks_remove_posix(filp, files);
error = -EBADF;
}
}
out:
locks_free_lock(file_lock);
return error;
}
#endif /* BITS_PER_LONG == 32 */
/*
* This function is called when the file is being removed
* from the task's fd array. POSIX locks belonging to this task
* are deleted at this time.
*/
void locks_remove_posix(struct file *filp, fl_owner_t owner)
{
int error;
struct inode *inode = file_inode(filp);
struct file_lock lock;
struct file_lock_context *ctx;
/*
* If there are no locks held on this file, we don't need to call
* posix_lock_file(). Another process could be setting a lock on this
* file at the same time, but we wouldn't remove that lock anyway.
*/
ctx = locks_inode_context(inode);
if (!ctx || list_empty(&ctx->flc_posix))
return;
locks_init_lock(&lock);
lock.c.flc_type = F_UNLCK;
lock.c.flc_flags = FL_POSIX | FL_CLOSE;
lock.fl_start = 0;
lock.fl_end = OFFSET_MAX;
lock.c.flc_owner = owner;
lock.c.flc_pid = current->tgid;
lock.c.flc_file = filp;
lock.fl_ops = NULL;
lock.fl_lmops = NULL;
error = vfs_lock_file(filp, F_SETLK, &lock, NULL);
if (lock.fl_ops && lock.fl_ops->fl_release_private)
lock.fl_ops->fl_release_private(&lock);
trace_locks_remove_posix(inode, &lock, error);
}
EXPORT_SYMBOL(locks_remove_posix);
/* The i_flctx must be valid when calling into here */
static void
locks_remove_flock(struct file *filp, struct file_lock_context *flctx)
{
struct file_lock fl;
struct inode *inode = file_inode(filp);
if (list_empty(&flctx->flc_flock))
return;
flock_make_lock(filp, &fl, F_UNLCK);
fl.c.flc_flags |= FL_CLOSE;
if (filp->f_op->flock)
filp->f_op->flock(filp, F_SETLKW, &fl);
else
flock_lock_inode(inode, &fl);
if (fl.fl_ops && fl.fl_ops->fl_release_private)
fl.fl_ops->fl_release_private(&fl);
}
/* The i_flctx must be valid when calling into here */
static void
locks_remove_lease(struct file *filp, struct file_lock_context *ctx)
{
struct file_lease *fl, *tmp;
LIST_HEAD(dispose);
if (list_empty(&ctx->flc_lease))
return;
percpu_down_read(&file_rwsem);
spin_lock(&ctx->flc_lock);
list_for_each_entry_safe(fl, tmp, &ctx->flc_lease, c.flc_list)
if (filp == fl->c.flc_file)
lease_modify(fl, F_UNLCK, &dispose);
spin_unlock(&ctx->flc_lock);
percpu_up_read(&file_rwsem);
locks_dispose_list(&dispose);
}
/*
* This function is called on the last close of an open file.
*/
void locks_remove_file(struct file *filp)
{
struct file_lock_context *ctx;
ctx = locks_inode_context(file_inode(filp));
if (!ctx)
return;
/* remove any OFD locks */
locks_remove_posix(filp, filp);
/* remove flock locks */
locks_remove_flock(filp, ctx);
/* remove any leases */
locks_remove_lease(filp, ctx);
spin_lock(&ctx->flc_lock);
locks_check_ctx_file_list(filp, &ctx->flc_posix, "POSIX");
locks_check_ctx_file_list(filp, &ctx->flc_flock, "FLOCK");
locks_check_ctx_file_list(filp, &ctx->flc_lease, "LEASE");
spin_unlock(&ctx->flc_lock);
}
/**
* vfs_cancel_lock - file byte range unblock lock
* @filp: The file to apply the unblock to
* @fl: The lock to be unblocked
*
* Used by lock managers to cancel blocked requests
*/
int vfs_cancel_lock(struct file *filp, struct file_lock *fl)
{
WARN_ON_ONCE(filp != fl->c.flc_file);
if (filp->f_op->lock)
return filp->f_op->lock(filp, F_CANCELLK, fl);
return 0;
}
EXPORT_SYMBOL_GPL(vfs_cancel_lock);
/**
* vfs_inode_has_locks - are any file locks held on @inode?
* @inode: inode to check for locks
*
* Return true if there are any FL_POSIX or FL_FLOCK locks currently
* set on @inode.
*/
bool vfs_inode_has_locks(struct inode *inode)
{
struct file_lock_context *ctx;
bool ret;
ctx = locks_inode_context(inode);
if (!ctx)
return false;
spin_lock(&ctx->flc_lock);
ret = !list_empty(&ctx->flc_posix) || !list_empty(&ctx->flc_flock);
spin_unlock(&ctx->flc_lock);
return ret;
}
EXPORT_SYMBOL_GPL(vfs_inode_has_locks);
#ifdef CONFIG_PROC_FS
#include <linux/proc_fs.h>
#include <linux/seq_file.h>
struct locks_iterator {
int li_cpu;
loff_t li_pos;
};
static void lock_get_status(struct seq_file *f, struct file_lock_core *flc,
loff_t id, char *pfx, int repeat)
{
struct inode *inode = NULL;
unsigned int pid;
struct pid_namespace *proc_pidns = proc_pid_ns(file_inode(f->file)->i_sb);
int type = flc->flc_type;
struct file_lock *fl = file_lock(flc);
pid = locks_translate_pid(flc, proc_pidns);
/*
* If lock owner is dead (and pid is freed) or not visible in current
* pidns, zero is shown as a pid value. Check lock info from
* init_pid_ns to get saved lock pid value.
*/
if (flc->flc_file != NULL)
inode = file_inode(flc->flc_file);
seq_printf(f, "%lld: ", id);
if (repeat)
seq_printf(f, "%*s", repeat - 1 + (int)strlen(pfx), pfx);
if (flc->flc_flags & FL_POSIX) {
if (flc->flc_flags & FL_ACCESS)
seq_puts(f, "ACCESS");
else if (flc->flc_flags & FL_OFDLCK)
seq_puts(f, "OFDLCK");
else
seq_puts(f, "POSIX ");
seq_printf(f, " %s ",
(inode == NULL) ? "*NOINODE*" : "ADVISORY ");
} else if (flc->flc_flags & FL_FLOCK) {
seq_puts(f, "FLOCK ADVISORY ");
} else if (flc->flc_flags & (FL_LEASE|FL_DELEG|FL_LAYOUT)) {
struct file_lease *lease = file_lease(flc);
type = target_leasetype(lease);
if (flc->flc_flags & FL_DELEG)
seq_puts(f, "DELEG ");
else
seq_puts(f, "LEASE ");
if (lease_breaking(lease))
seq_puts(f, "BREAKING ");
else if (flc->flc_file)
seq_puts(f, "ACTIVE ");
else
seq_puts(f, "BREAKER ");
} else {
seq_puts(f, "UNKNOWN UNKNOWN ");
}
seq_printf(f, "%s ", (type == F_WRLCK) ? "WRITE" :
(type == F_RDLCK) ? "READ" : "UNLCK");
if (inode) {
/* userspace relies on this representation of dev_t */
seq_printf(f, "%d %02x:%02x:%lu ", pid,
MAJOR(inode->i_sb->s_dev),
MINOR(inode->i_sb->s_dev), inode->i_ino);
} else {
seq_printf(f, "%d <none>:0 ", pid);
}
if (flc->flc_flags & FL_POSIX) {
if (fl->fl_end == OFFSET_MAX)
seq_printf(f, "%Ld EOF\n", fl->fl_start);
else
seq_printf(f, "%Ld %Ld\n", fl->fl_start, fl->fl_end);
} else {
seq_puts(f, "0 EOF\n");
}
}
static struct file_lock_core *get_next_blocked_member(struct file_lock_core *node)
{
struct file_lock_core *tmp;
/* NULL node or root node */
if (node == NULL || node->flc_blocker == NULL)
return NULL;
/* Next member in the linked list could be itself */
tmp = list_next_entry(node, flc_blocked_member);
if (list_entry_is_head(tmp, &node->flc_blocker->flc_blocked_requests,
flc_blocked_member)
|| tmp == node) {
return NULL;
}
return tmp;
}
static int locks_show(struct seq_file *f, void *v)
{
struct locks_iterator *iter = f->private;
struct file_lock_core *cur, *tmp;
struct pid_namespace *proc_pidns = proc_pid_ns(file_inode(f->file)->i_sb);
int level = 0;
cur = hlist_entry(v, struct file_lock_core, flc_link);
if (locks_translate_pid(cur, proc_pidns) == 0)
return 0;
/* View this crossed linked list as a binary tree, the first member of flc_blocked_requests
* is the left child of current node, the next silibing in flc_blocked_member is the
* right child, we can alse get the parent of current node from flc_blocker, so this
* question becomes traversal of a binary tree
*/
while (cur != NULL) {
if (level)
lock_get_status(f, cur, iter->li_pos, "-> ", level);
else
lock_get_status(f, cur, iter->li_pos, "", level);
if (!list_empty(&cur->flc_blocked_requests)) {
/* Turn left */
cur = list_first_entry_or_null(&cur->flc_blocked_requests,
struct file_lock_core,
flc_blocked_member);
level++;
} else {
/* Turn right */
tmp = get_next_blocked_member(cur);
/* Fall back to parent node */
while (tmp == NULL && cur->flc_blocker != NULL) {
cur = cur->flc_blocker;
level--;
tmp = get_next_blocked_member(cur);
}
cur = tmp;
}
}
return 0;
}
static void __show_fd_locks(struct seq_file *f,
struct list_head *head, int *id,
struct file *filp, struct files_struct *files)
{
struct file_lock_core *fl;
list_for_each_entry(fl, head, flc_list) {
if (filp != fl->flc_file)
continue;
if (fl->flc_owner != files && fl->flc_owner != filp)
continue;
(*id)++;
seq_puts(f, "lock:\t");
lock_get_status(f, fl, *id, "", 0);
}
}
void show_fd_locks(struct seq_file *f,
struct file *filp, struct files_struct *files)
{
struct inode *inode = file_inode(filp);
struct file_lock_context *ctx;
int id = 0;
ctx = locks_inode_context(inode);
if (!ctx)
return;
spin_lock(&ctx->flc_lock);
__show_fd_locks(f, &ctx->flc_flock, &id, filp, files);
__show_fd_locks(f, &ctx->flc_posix, &id, filp, files);
__show_fd_locks(f, &ctx->flc_lease, &id, filp, files);
spin_unlock(&ctx->flc_lock);
}
static void *locks_start(struct seq_file *f, loff_t *pos)
__acquires(&blocked_lock_lock)
{
struct locks_iterator *iter = f->private;
iter->li_pos = *pos + 1;
percpu_down_write(&file_rwsem);
spin_lock(&blocked_lock_lock);
return seq_hlist_start_percpu(&file_lock_list.hlist, &iter->li_cpu, *pos);
}
static void *locks_next(struct seq_file *f, void *v, loff_t *pos)
{
struct locks_iterator *iter = f->private;
++iter->li_pos;
return seq_hlist_next_percpu(v, &file_lock_list.hlist, &iter->li_cpu, pos);
}
static void locks_stop(struct seq_file *f, void *v)
__releases(&blocked_lock_lock)
{
spin_unlock(&blocked_lock_lock);
percpu_up_write(&file_rwsem);
}
static const struct seq_operations locks_seq_operations = {
.start = locks_start,
.next = locks_next,
.stop = locks_stop,
.show = locks_show,
};
static int __init proc_locks_init(void)
{
proc_create_seq_private("locks", 0, NULL, &locks_seq_operations,
sizeof(struct locks_iterator), NULL);
return 0;
}
fs_initcall(proc_locks_init);
#endif
static int __init filelock_init(void)
{
int i;
flctx_cache = kmem_cache_create("file_lock_ctx",
sizeof(struct file_lock_context), 0, SLAB_PANIC, NULL);
filelock_cache = kmem_cache_create("file_lock_cache",
sizeof(struct file_lock), 0, SLAB_PANIC, NULL);
filelease_cache = kmem_cache_create("file_lease_cache",
sizeof(struct file_lease), 0, SLAB_PANIC, NULL);
for_each_possible_cpu(i) {
struct file_lock_list_struct *fll = per_cpu_ptr(&file_lock_list, i);
spin_lock_init(&fll->lock);
INIT_HLIST_HEAD(&fll->hlist);
}
lease_notifier_chain_init();
return 0;
}
core_initcall(filelock_init);
Codebase Browser
linux