ext4: mark FC as ineligible using an handle

Hi!

Changes since v1:
* only the second patch has been changed to drop the call to ext4_fc_mark_ineligible() in the error path. Commit text has also been adjusted accordingly.

And here's the original cover-letter:

The following patches were suggested by Jan Kara[1] some time ago. Basically, they try to address a race that exists in several places, where function ext4_fc_mark_ineligible() is called with a NULL handle: in these cases, marking the filesystem as ineligible may effectively happen _after_ the fast-commit is done.

There are several places where this happen, and the two patches that follow try to address some of them. The first patch fixes the calls that exist in __track_dentry_update().

The second patch _partially_ fixes the call in ext4_xattr_set() -- this is because it may fail to obtain an handle. And, to be honest, I'm not sure what to do in this case: try again to obtain a new handle just for marking the fc, with a lower value for credits? or leave it as-is, with the NULL?

The other two missing callers are the ioctl for filesystem resize and ext4_evict_inode().

[1] https://lore.kernel.org/all/20240724101504.e2t4pvgw6td7rrmm@quack3/

Luis Henriques (SUSE) (2):
ext4: use handle to mark fc as ineligible in __track_dentry_update()
ext4: mark fc as ineligible using an handle in ext4_xattr_set()

 fs/ext4/fast_commit.c | 19 +++++++++++--------
 fs/ext4/xattr.c       |  3 ++-
 2 files changed, 13 insertions(+), 9 deletions(-)