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

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Message-ID: <HE1P191MB021916F9655748D8322308B2A5AF0@HE1P191MB0219.EURP191.PROD.OUTLOOK.COM>
Date:   Thu, 7 Jan 2021 10:29:08 +0000
From:   Mikael Szreder <miksz574@...dent.liu.se>
To:     Phillip Lougher <phillip@...ashfs.org.uk>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: [PATCH] fs/squashfs: Remove caching of errors in squashfs.

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@...dent.liu.se>
---
 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