From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Jerome Marchand , Nitin Gupta , Pekka Enberg , Minchan Kim Subject: [ 030/150] zram: Fix deadlock bug in partial read/write Date: Tue, 26 Feb 2013 15:54:47 -0800 Message-Id: <20130226235527.355720207@linuxfoundation.org> In-Reply-To: <20130226235523.930663721@linuxfoundation.org> References: <20130226235523.930663721@linuxfoundation.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: 3.8-stable review patch. If anyone has any objections, please let me know. ------------------ From: Minchan Kim 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 Acked-by: Nitin Gupta [ penberg@kernel.org: don't use GFP_ATOMIC ] Signed-off-by: Pekka Enberg Signed-off-by: Minchan Kim Signed-off-by: Greg Kroah-Hartman --- 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 @@ -228,11 +228,12 @@ static int zram_bvec_read(struct zram *z 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) { @@ -279,7 +280,7 @@ 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;