Messages in this thread Patch in this message | | | From | Minchan Kim <> | Subject | [PATCH v6 1/4] zram: Fix deadlock bug in partial read/write | Date | Wed, 30 Jan 2013 11:41:39 +0900 |
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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 Cc: Jerome Marchand <jmarchan@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> --- drivers/staging/zram/zram_drv.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-)
diff --git a/drivers/staging/zram/zram_drv.c b/drivers/staging/zram/zram_drv.c index 77a3f0d..5ff8749 100644 --- a/drivers/staging/zram/zram_drv.c +++ b/drivers/staging/zram/zram_drv.c @@ -217,11 +217,12 @@ static int zram_bvec_read(struct zram *zram, struct bio_vec *bvec, return 0; } - user_mem = kmap_atomic(page); if (is_partial_io(bvec)) /* Use a temporary buffer to decompress the page */ - uncmem = kmalloc(PAGE_SIZE, GFP_KERNEL); - else + uncmem = kmalloc(PAGE_SIZE, GFP_NOIO); + + user_mem = kmap_atomic(page); + if (!is_partial_io(bvec)) uncmem = user_mem; if (!uncmem) { @@ -268,7 +269,7 @@ static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index, * 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; -- 1.7.9.5
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