zram: Fix deadlock bug in partial read/write
authorMinchan Kim <minchan@kernel.org>
Wed, 30 Jan 2013 02:41:39 +0000 (11:41 +0900)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Mon, 4 Feb 2013 01:52:49 +0000 (17:52 -0800)
commit7e5a5104c6af709a8d97d5f4711e7c917761d464
tree0813b4b28b95db4547daaa60757c144cc4a1a77f
parent7f70410fe03f9f31a99bb5074b5e3c48f3b90541
zram: Fix deadlock bug in partial read/write

Now zram allocates new page with GFP_KERNEL in zram I/O path
if IO is partial. Unfortunately, It may cause deadlock with
reclaim path like below.

write_page from fs
fs_lock
allocation(GFP_KERNEL)
reclaim
pageout
write_page from fs
fs_lock <-- deadlock

This patch fixes it by using GFP_NOIO.  In read path, we
reorganize code flow so that kmap_atomic is called after the
GFP_NOIO allocation.

Cc: stable@vger.kernel.org
Acked-by: Jerome Marchand <jmarchand@redhat.com>
Acked-by: Nitin Gupta <ngupta@vflare.org>
[ penberg@kernel.org: don't use GFP_ATOMIC ]
Signed-off-by: Pekka Enberg <penberg@kernel.org>
Signed-off-by: Minchan Kim <minchan@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
drivers/staging/zram/zram_drv.c