From: Minchan Kim minchan@kernel.org Subject: zram: fix broken page writeback
commit 0d8359620d9b ("zram: support page writeback") introduced two problems. It overwrites writeback_store's return value as kstrtol's return value, which makes return value zero so user could see zero as return value of write syscall even though it wrote data successfully.
It also breaks index value in the loop in that it doesn't increase the index any longer. It means it can write only first starting block index so user couldn't write all idle pages in the zram so lose memory saving chance.
This patch fixes those issues.
Link: https://lkml.kernel.org/r/20210312173949.2197662-2-minchan@kernel.org Fixes: 0d8359620d9b("zram: support page writeback") Signed-off-by: Minchan Kim minchan@kernel.org Reported-by: Amos Bianchi amosbianchi@google.com Cc: Sergey Senozhatsky sergey.senozhatsky@gmail.com Cc: John Dias joaodias@google.com Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org ---
drivers/block/zram/zram_drv.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)
--- a/drivers/block/zram/zram_drv.c~zram-fix-broken-page-writeback +++ a/drivers/block/zram/zram_drv.c @@ -638,8 +638,8 @@ static ssize_t writeback_store(struct de if (strncmp(buf, PAGE_WB_SIG, sizeof(PAGE_WB_SIG) - 1)) return -EINVAL;
- ret = kstrtol(buf + sizeof(PAGE_WB_SIG) - 1, 10, &index); - if (ret || index >= nr_pages) + if (kstrtol(buf + sizeof(PAGE_WB_SIG) - 1, 10, &index) || + index >= nr_pages) return -EINVAL;
nr_pages = 1; @@ -663,7 +663,7 @@ static ssize_t writeback_store(struct de goto release_init_lock; }
- while (nr_pages--) { + for (; nr_pages != 0; index++, nr_pages--) { struct bio_vec bvec;
bvec.bv_page = page; _