| Date | Mon, 04 Mar 2013 03:37:29 +0000 | From | Ben Hutchings <> | Subject | [ 022/153] zram: Fix deadlock bug in partial read/write |
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3.2-stable review patch. If anyone has any objections, please let me know.
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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> --- 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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