[PATCH] fs/squashfs: Remove caching of errors in squashfs.

[Mikael Szreder]

This is a resubmit of this patch, originally sent on the 19 Oct 2020.

If squashfs encounters a read error when reading a block this error will
be cached. When the underlying problem that caused this error is fixed,
squashfs will still report the previous error, even though, a re-read
would now be successful.

This patch fixes this by setting the block field of the cache entry to
SQUASHFS_INVALID_BLK if an error was encountered. This prevents the cache
entry lookup from simply returning the cache entry with the previous error.

With this patch a mounted squashfs file system can recover from read
errors. Whereas previously this would have required a full remount.

Signed-off-by: Mikael Szreder <miksz574@xxxxxxxxxxxxxx>
---
 fs/squashfs/cache.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/fs/squashfs/cache.c b/fs/squashfs/cache.c
index 5062326d0efb..020fded42a6b 100644
--- a/fs/squashfs/cache.c
+++ b/fs/squashfs/cache.c
@@ -112,8 +112,10 @@ struct squashfs_cache_entry *squashfs_cache_get(struct super_block *sb,
 
                         spin_lock(&cache->lock);
 
-                       if (entry->length < 0)
+                       if (entry->length < 0) {
+                               entry->block = SQUASHFS_INVALID_BLK;
                                 entry->error = entry->length;
+                       }
 
                         entry->pending = 0;
 
-- 
2.28.0