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netfs: Fix ceph copy to cache on write-begin

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[ 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: 796a404964 ("netfs: In readahead, put the folio refs as soon extracted")
Reported-by: Max Kellermann <max.kellermann@ionos.com>
Closes: https://lore.kernel.org/r/CAKPOu+_4m80thNy5_fvROoxBm689YtA0dZ-=gcmkzwYSY4syqw@mail.gmail.com/
Signed-off-by: David Howells <dhowells@redhat.com>
Link: https://lore.kernel.org/r/20241213135013.2964079-10-dhowells@redhat.com
Fixes: ee4cdf7ba8 ("netfs: Speed up buffered reading")
cc: Jeff Layton <jlayton@kernel.org>
cc: Ilya Dryomov <idryomov@gmail.com>
cc: Xiubo Li <xiubli@redhat.com>
cc: netfs@lists.linux.dev
cc: ceph-devel@vger.kernel.org
cc: linux-fsdevel@vger.kernel.org
Signed-off-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
David Howells
2024-12-13 13:50:09 +00:00
committed by Greg Kroah-Hartman
parent 2c3348864a
commit 43b8d3249b
1 changed files with 4 additions and 2 deletions
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6
fs/netfs/read_collect.c
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@@ -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);
}
/*