zswap: don't param_set_charp while holding spinlock
authorDan Streetman <ddstreet@ieee.org>
Mon, 27 Feb 2017 22:26:53 +0000 (14:26 -0800)
committerLinus Torvalds <torvalds@linux-foundation.org>
Tue, 28 Feb 2017 02:43:45 +0000 (18:43 -0800)
commitfd5bb66cd934987e49557455b6497fc006521940
treed238fc3900b464c335b8719703ee1bfd9743c719
parentbae21db88b7075662f28a0aa57e97016a2fdabfd
zswap: don't param_set_charp while holding spinlock

Change the zpool/compressor param callback function to release the
zswap_pools_lock spinlock before calling param_set_charp, since that
function may sleep when it calls kmalloc with GFP_KERNEL.

While this problem has existed for a while, I wasn't able to trigger it
using a tight loop changing either/both the zpool and compressor params; I
think it's very unlikely to be an issue on the stable kernels, especially
since most zswap users will change the compressor and/or zpool from sysfs
only one time each boot - or zero times, if they add the params to the
kernel boot.

Fixes: c99b42c3529e ("zswap: use charp for zswap param strings")
Link: http://lkml.kernel.org/r/20170126155821.4545-1-ddstreet@ieee.org
Signed-off-by: Dan Streetman <dan.streetman@canonical.com>
Reported-by: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Minchan Kim <minchan@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
mm/zswap.c