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Message-Id: <20130304033709.738060965@decadent.org.uk>
Date: Mon, 04 Mar 2013 03:37:29 +0000
From: Ben Hutchings <ben@...adent.org.uk>
To: linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc: akpm@...ux-foundation.org, Minchan Kim <minchan@...nel.org>,
Jerome Marchand <jmarchand@...hat.com>,
Nitin Gupta <ngupta@...are.org>,
Pekka Enberg <penberg@...nel.org>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: [ 022/153] zram: Fix deadlock bug in partial read/write
3.2-stable review patch. If anyone has any objections, please let me know.
------------------
From: Minchan Kim <minchan@...nel.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@...hat.com>
Acked-by: Nitin Gupta <ngupta@...are.org>
[ penberg@...nel.org: don't use GFP_ATOMIC ]
Signed-off-by: Pekka Enberg <penberg@...nel.org>
Signed-off-by: Minchan Kim <minchan@...nel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
[bwh: Backported to 3.2: no reordering is needed in the read path]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
drivers/staging/zram/zram_drv.c | 9 +++++----
1 file changed, 5 insertions(+), 4 deletions(-)
--- a/drivers/staging/zram/zram_drv.c
+++ b/drivers/staging/zram/zram_drv.c
@@ -242,7 +242,7 @@ 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;
@@ -338,7 +338,7 @@ 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;
--
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