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SubjectRe: [PATCH v6 1/4] zram: Fix deadlock bug in partial read/write
On 01/30/2013 03:41 AM, Minchan Kim wrote:
> 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.

For the all series:
Acked-by: Jerome Marchand <jmarchand@redhat.com>

>
> 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;
>



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