fs: Remove inode lock from __generic_file_fsync()

Inode lock in __generic_file_fsync() protects sync_mapping_buffers() and
sync_inode_metadata() calls. Neither sync_mapping_buffers() nor
sync_inode_metadata() themselves need the protection by inode_lock and
both metadata buffer head writeback and inode writeback can happen
without inode lock (either in case of background writeback or sync(2)
calls). The only protection inode_lock can possibly provide is that
write(2) or other inode modifying calls cannot happen in the middle of
bh+inode writeout and thus result in writeout of inconsistent metadata.
However if writes and fsyncs race, background writeback can submit
inconsistent metadata just after fsync completed even with inode_lock
protecting fsync so this seems moot as well. So let's remove the
apparently pointless inode_lock protection.

Signed-off-by: Jan Kara <jack@suse.cz>
Link: https://patch.msgid.link/20260326095354.16340-50-jack@suse.cz
Signed-off-by: Christian Brauner <brauner@kernel.org>

diff --git a/fs/libfs.c b/fs/libfs.c
index 74134ba2e8d1e67b88b3a07841f927a4a411988f..ed7242d614fe2737755c2edd3f64930cb19d4da4 100644 (file)
--- a/fs/libfs.c
+++ b/fs/libfs.c
@@ -1561,7 +1561,6 @@ int __generic_file_fsync(struct file *file, loff_t start, loff_t end,
        if (err)
                return err;
 
-       inode_lock(inode);
        ret = sync_mapping_buffers(inode->i_mapping);
        if (!(inode_state_read_once(inode) & I_DIRTY_ALL))
                goto out;
@@ -1573,7 +1572,6 @@ int __generic_file_fsync(struct file *file, loff_t start, loff_t end,
                ret = err;
 
 out:
-       inode_unlock(inode);
        /* check and advance again to catch errors after syncing out buffers */
        err = file_check_and_advance_wb_err(file);
        if (ret == 0)