[PATCH 3.4 102/214] zram: Fix deadlock bug in partial read/write

Greg Kroah-Hartman
2014-06-05T04:21:09Z

From: Minchan Kim <minchan@kernel.org>

commit 7e5a5104c6af709a8d97d5f4711e7c917761d464 upstream.

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.

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>
[bwh: Backported to 3.2: no reordering is needed in the read path]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Cc: Jianguo Wu <wujianguo@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/staging/zram/zram_drv.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

--- a/drivers/staging/zram/zram_drv.c
+++ b/drivers/staging/zram/zram_drv.c
@@ -235,7 +235,7 @@ static int zram_bvec_read(struct zram *z

if (is_partial_io(bvec)) {
/* Use a temporary buffer to decompress the page */
- uncmem = kmalloc(PAGE_SIZE, GFP_KERNEL);
+ uncmem = kmalloc(PAGE_SIZE, GFP_NOIO);
if (!uncmem) {
pr_info("Error allocating temp memory!\n");
return -ENOMEM;
@@ -330,7 +330,7 @@ static int zram_bvec_write(struct zram *
* This is a partial IO. We need to read the full page
* before to write the changes.
*/
- uncmem = kmalloc(PAGE_SIZE, GFP_KERNEL);
+ uncmem = kmalloc(PAGE_SIZE, GFP_NOIO);
if (!uncmem) {
pr_info("Error allocating temp memory!\n");
ret = -ENOMEM;