[PATCH v6 8/9] btrfs: convert to multigrain timestamps

Jeff Layton
2024-07-15T12:49:34Z

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>
Signed-off-by: Jeff Layton <jlayton@kernel.org>
---
fs/btrfs/file.c | 25 ++++---------------------
fs/btrfs/super.c | 3 ++-
2 files changed, 6 insertions(+), 22 deletions(-)

diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index d90138683a0a..409628c0c3cc 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);
-}
-
static int btrfs_write_check(struct kiocb *iocb, struct iov_iter *from,
size_t count)
{
@@ -1171,7 +1151,10 @@ static int btrfs_write_check(struct kiocb *iocb, struct iov_iter *from,
* 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 f05cce7c8b8d..1cd50293b98d 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -2173,7 +2173,8 @@ 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");

--
2.45.2