netfs: Fix ceph copy to cache on write-begin

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 <[email protected]>
Closes: https://lore.kernel.org/r/CAKPOu+_4m80thNy5_fvROoxBm689YtA0dZ-=gcmkzwYSY4syqw@mail.gmail.com/
Signed-off-by: David Howells <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Fixes: ee4cdf7ba857 ("netfs: Speed up buffered reading")
cc: Jeff Layton <[email protected]>
cc: Ilya Dryomov <[email protected]>
cc: Xiubo Li <[email protected]>
cc: [email protected]
cc: [email protected]
cc: [email protected]
Signed-off-by: Christian Brauner <[email protected]>

0 files changed, 0 insertions, 0 deletions