Estimated time of removal of the functionality is 5.11, the option will
be still parsed but not doing anything.
Reasons for deprecation and removal:
- very poor naming choice of the mount option, it's supposed to cache
and reuse the inode _numbers_, but it sounds a some generic cache for
inodes
- the only known usecase where this option would make sense is on a
32bit architecture where inode numbers in one subvolume would be
exhausted due to 32bit inode::i_ino
- the cache is stored on disk, consumes space, needs to be loaded and
written back
- new inode number allocation is slower due to lookups into the cache
(compared to a simple increment which is the default)
- uses the free-space-cache code that is going to be deprecated as well
in the future
Known problems:
- since 2011, returning EEXIST when there's not enough space in a page
to store all checksums, see commit 4b9465cb9e38 ("Btrfs: add mount -o
inode_cache")
Remaining issues:
- if the option was enabled, new inodes created, the option disabled
again, the cache is still stored on the devices and there's currently
no way to remove it
Signed-off-by: David Sterba <dsterba@xxxxxxxx>
---
fs/btrfs/super.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index 98fe2a634c70..3f1abbeef66c 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -827,6 +827,8 @@ int btrfs_parse_options(struct btrfs_fs_info *info, char *options,
}
break;
case Opt_inode_cache:
+ btrfs_warn(info,
+ "the 'inode_cache' option is deprecated and will be stop working in 5.11");
btrfs_set_pending_and_info(info, INODE_MAP_CACHE,
"enabling inode map caching");
break;
--
2.25.0
