From: Greg Kroah-Hartman gregkh@linuxfoundation.org
From: Minchan Kim minchan@kernel.org
commit 57e0076e6575a7b7cef620a0bd2ee2549ef77818 upstream.
writeback_store's return value is overwritten by submit_bio_wait's return value. Thus, writeback_store will return zero since there was no IO error. In the end, write syscall from userspace will see the zero as return value, which could make the process stall to keep trying the write until it will succeed.
Link: https://lkml.kernel.org/r/20210312173949.2197662-1-minchan@kernel.org Fixes: 3b82a051c101("drivers/block/zram/zram_drv.c: fix error return codes not being returned in writeback_store") Signed-off-by: Minchan Kim minchan@kernel.org Cc: Sergey Senozhatsky sergey.senozhatsky@gmail.com Cc: Colin Ian King colin.king@canonical.com Cc: John Dias joaodias@google.com Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/block/zram/zram_drv.c | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-)
--- a/drivers/block/zram/zram_drv.c +++ b/drivers/block/zram/zram_drv.c @@ -628,7 +628,7 @@ static ssize_t writeback_store(struct de struct bio_vec bio_vec; struct page *page; ssize_t ret = len; - int mode; + int mode, err; unsigned long blk_idx = 0;
if (sysfs_streq(buf, "idle")) @@ -729,12 +729,17 @@ static ssize_t writeback_store(struct de * XXX: A single page IO would be inefficient for write * but it would be not bad as starter. */ - ret = submit_bio_wait(&bio); - if (ret) { + err = submit_bio_wait(&bio); + if (err) { zram_slot_lock(zram, index); zram_clear_flag(zram, index, ZRAM_UNDER_WB); zram_clear_flag(zram, index, ZRAM_IDLE); zram_slot_unlock(zram, index); + /* + * Return last IO error unless every IO were + * not suceeded. + */ + ret = err; continue; }