From: Jeff Layton <jlayton@kernel.org>
Date: Wed, 2 Oct 2024 21:27:26 +0000 (-0400)
Subject: btrfs: convert to multigrain timestamps
X-Git-Tag: v6.13-rc1~231^2~1^2~1
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=e2e801d6e62507c297ec2c102e24d09c90618e8b;p=thirdparty%2Fkernel%2Flinux.git

btrfs: convert to multigrain timestamps

Enable multigrain timestamps, which should ensure that there is an
apparent change to the timestamp whenever it has been written after
being actively observed via getattr.

Beyond enabling the FS_MGTIME flag, this patch eliminates
update_time_for_write, which goes to great pains to avoid in-memory
stores. Just have it overwrite the timestamps unconditionally.

Note that this also drops the IS_I_VERSION check and unconditionally
bumps the change attribute, since SB_I_VERSION is always set on btrfs.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Tested-by: Randy Dunlap <rdunlap@infradead.org> # documentation bits
Signed-off-by: Jeff Layton <jlayton@kernel.org>
Link: https://lore.kernel.org/r/20241002-mgtime-v10-11-d1c4717f5284@kernel.org
Signed-off-by: Christian Brauner <brauner@kernel.org>
---

diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index 2aeb8116549ca..1656ad7498b81 100644
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -1120,26 +1120,6 @@ void btrfs_check_nocow_unlock(struct btrfs_inode *inode)
 	btrfs_drew_write_unlock(&inode->root->snapshot_lock);
 }
 
-static void update_time_for_write(struct inode *inode)
-{
-	struct timespec64 now, ts;
-
-	if (IS_NOCMTIME(inode))
-		return;
-
-	now = current_time(inode);
-	ts = inode_get_mtime(inode);
-	if (!timespec64_equal(&ts, &now))
-		inode_set_mtime_to_ts(inode, now);
-
-	ts = inode_get_ctime(inode);
-	if (!timespec64_equal(&ts, &now))
-		inode_set_ctime_to_ts(inode, now);
-
-	if (IS_I_VERSION(inode))
-		inode_inc_iversion(inode);
-}
-
 int btrfs_write_check(struct kiocb *iocb, struct iov_iter *from, size_t count)
 {
 	struct file *file = iocb->ki_filp;
@@ -1170,7 +1150,10 @@ int btrfs_write_check(struct kiocb *iocb, struct iov_iter *from, size_t count)
 	 * need to start yet another transaction to update the inode as we will
 	 * update the inode when we finish writing whatever data we write.
 	 */
-	update_time_for_write(inode);
+	if (!IS_NOCMTIME(inode)) {
+		inode_set_mtime_to_ts(inode, inode_set_ctime_current(inode));
+		inode_inc_iversion(inode);
+	}
 
 	start_pos = round_down(pos, fs_info->sectorsize);
 	oldsize = i_size_read(inode);
diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index 98fa0f382480a..d423acfe11d0d 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -2198,7 +2198,8 @@ static struct file_system_type btrfs_fs_type = {
 	.init_fs_context	= btrfs_init_fs_context,
 	.parameters		= btrfs_fs_parameters,
 	.kill_sb		= btrfs_kill_super,
-	.fs_flags		= FS_REQUIRES_DEV | FS_BINARY_MOUNTDATA | FS_ALLOW_IDMAP,
+	.fs_flags		= FS_REQUIRES_DEV | FS_BINARY_MOUNTDATA |
+				  FS_ALLOW_IDMAP | FS_MGTIME,
  };
 
 MODULE_ALIAS_FS("btrfs");