Btrfs: fix fsync data loss after a ranged fsync
While we're doing a full fsync (when the inode has the flag
BTRFS_INODE_NEEDS_FULL_SYNC set) that is ranged too (covers only a
portion of the file), we might have ordered operations that are started
before or while we're logging the inode and that fall outside the fsync
range.
Therefore when a full ranged fsync finishes don't remove every extent
map from the list of modified extent maps - as for some of them, that
fall outside our fsync range, their respective ordered operation hasn't
finished yet, meaning the corresponding file extent item wasn't inserted
into the fs/subvol tree yet and therefore we didn't log it, and we must
let the next fast fsync (one that checks only the modified list) see this
extent map and log a matching file extent item to the log btree and wait
for its ordered operation to finish (if it's still ongoing).
A test case for xfstests follows.
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Chris Mason <clm@fb.com>
diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index 36861b7..ff1cc03 100644
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -1966,7 +1966,7 @@
btrfs_init_log_ctx(&ctx);
- ret = btrfs_log_dentry_safe(trans, root, dentry, &ctx);
+ ret = btrfs_log_dentry_safe(trans, root, dentry, start, end, &ctx);
if (ret < 0) {
/* Fallthrough and commit/free transaction. */
ret = 1;
diff --git a/fs/btrfs/tree-log.c b/fs/btrfs/tree-log.c
index 7e0e6e3..d296efe 100644
--- a/fs/btrfs/tree-log.c
+++ b/fs/btrfs/tree-log.c
@@ -94,8 +94,10 @@
#define LOG_WALK_REPLAY_ALL 3
static int btrfs_log_inode(struct btrfs_trans_handle *trans,
- struct btrfs_root *root, struct inode *inode,
- int inode_only);
+ struct btrfs_root *root, struct inode *inode,
+ int inode_only,
+ const loff_t start,
+ const loff_t end);
static int link_to_fixup_dir(struct btrfs_trans_handle *trans,
struct btrfs_root *root,
struct btrfs_path *path, u64 objectid);
@@ -3858,8 +3860,10 @@
* This handles both files and directories.
*/
static int btrfs_log_inode(struct btrfs_trans_handle *trans,
- struct btrfs_root *root, struct inode *inode,
- int inode_only)
+ struct btrfs_root *root, struct inode *inode,
+ int inode_only,
+ const loff_t start,
+ const loff_t end)
{
struct btrfs_path *path;
struct btrfs_path *dst_path;
@@ -3876,6 +3880,7 @@
int ins_nr;
bool fast_search = false;
u64 ino = btrfs_ino(inode);
+ struct extent_map_tree *em_tree = &BTRFS_I(inode)->extent_tree;
path = btrfs_alloc_path();
if (!path)
@@ -4049,13 +4054,35 @@
goto out_unlock;
}
} else if (inode_only == LOG_INODE_ALL) {
- struct extent_map_tree *tree = &BTRFS_I(inode)->extent_tree;
struct extent_map *em, *n;
- write_lock(&tree->lock);
- list_for_each_entry_safe(em, n, &tree->modified_extents, list)
- list_del_init(&em->list);
- write_unlock(&tree->lock);
+ write_lock(&em_tree->lock);
+ /*
+ * We can't just remove every em if we're called for a ranged
+ * fsync - that is, one that doesn't cover the whole possible
+ * file range (0 to LLONG_MAX). This is because we can have
+ * em's that fall outside the range we're logging and therefore
+ * their ordered operations haven't completed yet
+ * (btrfs_finish_ordered_io() not invoked yet). This means we
+ * didn't get their respective file extent item in the fs/subvol
+ * tree yet, and need to let the next fast fsync (one which
+ * consults the list of modified extent maps) find the em so
+ * that it logs a matching file extent item and waits for the
+ * respective ordered operation to complete (if it's still
+ * running).
+ *
+ * Removing every em outside the range we're logging would make
+ * the next fast fsync not log their matching file extent items,
+ * therefore making us lose data after a log replay.
+ */
+ list_for_each_entry_safe(em, n, &em_tree->modified_extents,
+ list) {
+ const u64 mod_end = em->mod_start + em->mod_len - 1;
+
+ if (em->mod_start >= start && mod_end <= end)
+ list_del_init(&em->list);
+ }
+ write_unlock(&em_tree->lock);
}
if (inode_only == LOG_INODE_ALL && S_ISDIR(inode->i_mode)) {
@@ -4065,8 +4092,19 @@
goto out_unlock;
}
}
- BTRFS_I(inode)->logged_trans = trans->transid;
- BTRFS_I(inode)->last_log_commit = BTRFS_I(inode)->last_sub_trans;
+
+ write_lock(&em_tree->lock);
+ /*
+ * If we're doing a ranged fsync and there are still modified extents
+ * in the list, we must run on the next fsync call as it might cover
+ * those extents (a full fsync or an fsync for other range).
+ */
+ if (list_empty(&em_tree->modified_extents)) {
+ BTRFS_I(inode)->logged_trans = trans->transid;
+ BTRFS_I(inode)->last_log_commit =
+ BTRFS_I(inode)->last_sub_trans;
+ }
+ write_unlock(&em_tree->lock);
out_unlock:
if (unlikely(err))
btrfs_put_logged_extents(&logged_list);
@@ -4161,7 +4199,10 @@
*/
static int btrfs_log_inode_parent(struct btrfs_trans_handle *trans,
struct btrfs_root *root, struct inode *inode,
- struct dentry *parent, int exists_only,
+ struct dentry *parent,
+ const loff_t start,
+ const loff_t end,
+ int exists_only,
struct btrfs_log_ctx *ctx)
{
int inode_only = exists_only ? LOG_INODE_EXISTS : LOG_INODE_ALL;
@@ -4207,7 +4248,7 @@
if (ret)
goto end_no_trans;
- ret = btrfs_log_inode(trans, root, inode, inode_only);
+ ret = btrfs_log_inode(trans, root, inode, inode_only, start, end);
if (ret)
goto end_trans;
@@ -4235,7 +4276,8 @@
if (BTRFS_I(inode)->generation >
root->fs_info->last_trans_committed) {
- ret = btrfs_log_inode(trans, root, inode, inode_only);
+ ret = btrfs_log_inode(trans, root, inode, inode_only,
+ 0, LLONG_MAX);
if (ret)
goto end_trans;
}
@@ -4269,13 +4311,15 @@
*/
int btrfs_log_dentry_safe(struct btrfs_trans_handle *trans,
struct btrfs_root *root, struct dentry *dentry,
+ const loff_t start,
+ const loff_t end,
struct btrfs_log_ctx *ctx)
{
struct dentry *parent = dget_parent(dentry);
int ret;
ret = btrfs_log_inode_parent(trans, root, dentry->d_inode, parent,
- 0, ctx);
+ start, end, 0, ctx);
dput(parent);
return ret;
@@ -4512,6 +4556,7 @@
root->fs_info->last_trans_committed))
return 0;
- return btrfs_log_inode_parent(trans, root, inode, parent, 1, NULL);
+ return btrfs_log_inode_parent(trans, root, inode, parent, 0,
+ LLONG_MAX, 1, NULL);
}
diff --git a/fs/btrfs/tree-log.h b/fs/btrfs/tree-log.h
index 7f5b41b..e2e798a 100644
--- a/fs/btrfs/tree-log.h
+++ b/fs/btrfs/tree-log.h
@@ -59,6 +59,8 @@
int btrfs_recover_log_trees(struct btrfs_root *tree_root);
int btrfs_log_dentry_safe(struct btrfs_trans_handle *trans,
struct btrfs_root *root, struct dentry *dentry,
+ const loff_t start,
+ const loff_t end,
struct btrfs_log_ctx *ctx);
int btrfs_del_dir_entries_in_log(struct btrfs_trans_handle *trans,
struct btrfs_root *root,