From: David Howells <dhowells@redhat.com>
Date: Fri, 7 Jan 2022 10:51:13 +0000
Subject: cachefiles: Explain checks in a comment
Git-commit: 14b9d0902dfa25dac9c41bf346aa655fdeafe5b2
Patch-mainline: v5.17-rc1
References: jsc#SES-1880
Add a comment to explain the checks that cachefiles is making of the
backing filesystem[1].
Suggested-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
cc: linux-cachefs@redhat.com
Link: https://lore.kernel.org/r/568749bd7cc02908ecf6f3d6a611b6f9cf5c4afd.camel@kernel.org/ [1]
Link: https://lore.kernel.org/r/164251405621.3435901.771439791811515914.stgit@warthog.procyon.org.uk/ # v1
Acked-by: Luis Henriques <lhenriques@suse.com>
---
fs/cachefiles/cache.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)
diff --git a/fs/cachefiles/cache.c b/fs/cachefiles/cache.c
index 1e9c71666c6a..2b2879c5d1d2 100644
--- a/fs/cachefiles/cache.c
+++ b/fs/cachefiles/cache.c
@@ -49,7 +49,13 @@ int cachefiles_add_cache(struct cachefiles_cache *cache)
goto error_unsupported;
}
- /* check parameters */
+ /* Check features of the backing filesystem:
+ * - Directories must support looking up and directory creation
+ * - We use xattrs to store metadata
+ * - We need to be able to query the amount of space available
+ * - We want to be able to sync the filesystem when stopping the cache
+ * - We use DIO to/from pages, so the blocksize mustn't be too big.
+ */
ret = -EOPNOTSUPP;
if (d_is_negative(root) ||
!d_backing_inode(root)->i_op->lookup ||