linux/fs/btrfs/tree-mod-log.c

// SPDX-License-Identifier: GPL-2.0

#include "messages.h"
#include "tree-mod-log.h"
#include "disk-io.h"
#include "fs.h"
#include "accessors.h"
#include "tree-checker.h"

struct tree_mod_root { … };

struct tree_mod_elem { … };

/*
 * Pull a new tree mod seq number for our operation.
 */
static u64 btrfs_inc_tree_mod_seq(struct btrfs_fs_info *fs_info)
{ … }

/*
 * This adds a new blocker to the tree mod log's blocker list if the @elem
 * passed does not already have a sequence number set. So when a caller expects
 * to record tree modifications, it should ensure to set elem->seq to zero
 * before calling btrfs_get_tree_mod_seq.
 * Returns a fresh, unused tree log modification sequence number, even if no new
 * blocker was added.
 */
u64 btrfs_get_tree_mod_seq(struct btrfs_fs_info *fs_info,
			   struct btrfs_seq_list *elem)
{ … }

void btrfs_put_tree_mod_seq(struct btrfs_fs_info *fs_info,
			    struct btrfs_seq_list *elem)
{ … }

/*
 * Key order of the log:
 *       node/leaf start address -> sequence
 *
 * The 'start address' is the logical address of the *new* root node for root
 * replace operations, or the logical address of the affected block for all
 * other operations.
 */
static noinline int tree_mod_log_insert(struct btrfs_fs_info *fs_info,
					struct tree_mod_elem *tm)
{ … }

/*
 * Determines if logging can be omitted. Returns true if it can. Otherwise, it
 * returns false with the tree_mod_log_lock acquired. The caller must hold
 * this until all tree mod log insertions are recorded in the rb tree and then
 * write unlock fs_info::tree_mod_log_lock.
 */
static bool tree_mod_dont_log(struct btrfs_fs_info *fs_info, struct extent_buffer *eb)
{ … }

/* Similar to tree_mod_dont_log, but doesn't acquire any locks. */
static bool tree_mod_need_log(const struct btrfs_fs_info *fs_info,
				    struct extent_buffer *eb)
{ … }

static struct tree_mod_elem *alloc_tree_mod_elem(struct extent_buffer *eb,
						 int slot,
						 enum btrfs_mod_log_op op)
{ … }

int btrfs_tree_mod_log_insert_key(struct extent_buffer *eb, int slot,
				  enum btrfs_mod_log_op op)
{ … }

static struct tree_mod_elem *tree_mod_log_alloc_move(struct extent_buffer *eb,
						     int dst_slot, int src_slot,
						     int nr_items)
{ … }

int btrfs_tree_mod_log_insert_move(struct extent_buffer *eb,
				   int dst_slot, int src_slot,
				   int nr_items)
{ … }

static int tree_mod_log_free_eb(struct btrfs_fs_info *fs_info,
				struct tree_mod_elem **tm_list,
				int nritems)
{ … }

int btrfs_tree_mod_log_insert_root(struct extent_buffer *old_root,
				   struct extent_buffer *new_root,
				   bool log_removal)
{ … }

static struct tree_mod_elem *__tree_mod_log_search(struct btrfs_fs_info *fs_info,
						   u64 start, u64 min_seq,
						   bool smallest)
{ … }

/*
 * This returns the element from the log with the smallest time sequence
 * value that's in the log (the oldest log item). Any element with a time
 * sequence lower than min_seq will be ignored.
 */
static struct tree_mod_elem *tree_mod_log_search_oldest(struct btrfs_fs_info *fs_info,
							u64 start, u64 min_seq)
{ … }

/*
 * This returns the element from the log with the largest time sequence
 * value that's in the log (the most recent log item). Any element with
 * a time sequence lower than min_seq will be ignored.
 */
static struct tree_mod_elem *tree_mod_log_search(struct btrfs_fs_info *fs_info,
						 u64 start, u64 min_seq)
{ … }

int btrfs_tree_mod_log_eb_copy(struct extent_buffer *dst,
			       struct extent_buffer *src,
			       unsigned long dst_offset,
			       unsigned long src_offset,
			       int nr_items)
{ … }

int btrfs_tree_mod_log_free_eb(struct extent_buffer *eb)
{ … }

/*
 * Returns the logical address of the oldest predecessor of the given root.
 * Entries older than time_seq are ignored.
 */
static struct tree_mod_elem *tree_mod_log_oldest_root(struct extent_buffer *eb_root,
						      u64 time_seq)
{ … }


/*
 * tm is a pointer to the first operation to rewind within eb. Then, all
 * previous operations will be rewound (until we reach something older than
 * time_seq).
 */
static void tree_mod_log_rewind(struct btrfs_fs_info *fs_info,
				struct extent_buffer *eb,
				u64 time_seq,
				struct tree_mod_elem *first_tm)
{ … }

/*
 * Called with eb read locked. If the buffer cannot be rewound, the same buffer
 * is returned. If rewind operations happen, a fresh buffer is returned. The
 * returned buffer is always read-locked. If the returned buffer is not the
 * input buffer, the lock on the input buffer is released and the input buffer
 * is freed (its refcount is decremented).
 */
struct extent_buffer *btrfs_tree_mod_log_rewind(struct btrfs_fs_info *fs_info,
						struct btrfs_path *path,
						struct extent_buffer *eb,
						u64 time_seq)
{ … }

/*
 * Rewind the state of @root's root node to the given @time_seq value.
 * If there are no changes, the current root->root_node is returned. If anything
 * changed in between, there's a fresh buffer allocated on which the rewind
 * operations are done. In any case, the returned buffer is read locked.
 * Returns NULL on error (with no locks held).
 */
struct extent_buffer *btrfs_get_old_root(struct btrfs_root *root, u64 time_seq)
{ … }

int btrfs_old_root_level(struct btrfs_root *root, u64 time_seq)
{ … }

/*
 * Return the lowest sequence number in the tree modification log.
 *
 * Return the sequence number of the oldest tree modification log user, which
 * corresponds to the lowest sequence number of all existing users. If there are
 * no users it returns 0.
 */
u64 btrfs_tree_mod_log_lowest_seq(struct btrfs_fs_info *fs_info)
{ … }