This is a note to let you know that I've just added the patch titled
netfs: Fix ceph copy to cache on write-begin
to the 6.12-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
netfs-fix-ceph-copy-to-cache-on-write-begin.patch
and it can be found in the queue-6.12 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 5a499cd36c28f96ffffe9d6e5cb5b6ac734b5e8e
Author: David Howells <dhowells@xxxxxxxxxx>
Date: Fri Dec 13 13:50:09 2024 +0000
netfs: Fix ceph copy to cache on write-begin
[ Upstream commit 38cf8e945721ffe708fa675507465da7f4f2a9f7 ]
At the end of netfs_unlock_read_folio() in which folios are marked
appropriately for copying to the cache (either with by being marked dirty
and having their private data set or by having PG_private_2 set) and then
unlocked, the folio_queue struct has the entry pointing to the folio
cleared. This presents a problem for netfs_pgpriv2_write_to_the_cache(),
which is used to write folios marked with PG_private_2 to the cache as it
expects to be able to trawl the folio_queue list thereafter to find the
relevant folios, leading to a hang.
Fix this by not clearing the folio_queue entry if we're going to do the
deprecated copy-to-cache. The clearance will be done instead as the folios
are written to the cache.
This can be reproduced by starting cachefiles, mounting a ceph filesystem
with "-o fsc" and writing to it.
Fixes: 796a4049640b ("netfs: In readahead, put the folio refs as soon extracted")
Reported-by: Max Kellermann <max.kellermann@xxxxxxxxx>
Closes: https://lore.kernel.org/r/CAKPOu+_4m80thNy5_fvROoxBm689YtA0dZ-=gcmkzwYSY4syqw@xxxxxxxxxxxxxx/
Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20241213135013.2964079-10-dhowells@xxxxxxxxxx
Fixes: ee4cdf7ba857 ("netfs: Speed up buffered reading")
cc: Jeff Layton <jlayton@xxxxxxxxxx>
cc: Ilya Dryomov <idryomov@xxxxxxxxx>
cc: Xiubo Li <xiubli@xxxxxxxxxx>
cc: netfs@xxxxxxxxxxxxxxx
cc: ceph-devel@xxxxxxxxxxxxxxx
cc: linux-fsdevel@xxxxxxxxxxxxxxx
Signed-off-by: Christian Brauner <brauner@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/fs/netfs/read_collect.c b/fs/netfs/read_collect.c
index d86fa02f68fb..e70eb4ea21c0 100644
--- a/fs/netfs/read_collect.c
+++ b/fs/netfs/read_collect.c
@@ -62,10 +62,14 @@ static void netfs_unlock_read_folio(struct netfs_io_subrequest *subreq,
} else {
trace_netfs_folio(folio, netfs_folio_trace_read_done);
}
+
+ folioq_clear(folioq, slot);
} else {
// TODO: Use of PG_private_2 is deprecated.
if (test_bit(NETFS_SREQ_COPY_TO_CACHE, &subreq->flags))
netfs_pgpriv2_mark_copy_to_cache(subreq, rreq, folioq, slot);
+ else
+ folioq_clear(folioq, slot);
}
if (!test_bit(NETFS_RREQ_DONT_UNLOCK_FOLIOS, &rreq->flags)) {
@@ -77,8 +81,6 @@ static void netfs_unlock_read_folio(struct netfs_io_subrequest *subreq,
folio_unlock(folio);
}
}
-
- folioq_clear(folioq, slot);
}
/*
