cachefiles: Explain checks in a comment

Add a comment to explain the checks that cachefiles is making of the backing filesystem[1]. Suggested-by: Jeff Layton <[email protected]> Signed-off-by: David Howells <[email protected]> Reviewed-by: Jeff Layton <[email protected]> cc: [email protected] Link: https://lore.kernel.org/r/[email protected]/ [1] Link: https://lore.kernel.org/r/164251405621.3435901.771439791811515914.stgit@warthog.procyon.org.uk/ # v1
wafgo · Jan 21, 2022 · 14b9d09 · 14b9d09
1 parent b64a331
commit 14b9d09
Showing 1 changed file with 7 additions and 1 deletion.
diff --git 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 ||