On Thu, Jan 07, 2016 at 04:03:04PM +0100, Jan Kara wrote:
> Currently we dropped freeze protection of aio writes just after IO was
> submitted. Thus aio write could be in flight while the filesystem was
> frozen and that could result in unexpected situation like aio completion
> wanting to convert extent type on frozen filesystem. Testcase from
> Dmitry triggering this is like:
>
> for ((i=0;i<60;i++));do fsfreeze -f /mnt ;sleep 1;fsfreeze -u /mnt;done &
> fio --bs=4k --ioengine=libaio --iodepth=128 --size=1g --direct=1 \
> --runtime=60 --filename=/mnt/file --name=rand-write --rw=randwrite
>
> Fix the problem by dropping freeze protection only once IO is completed
> in aio_complete().
Why isn't this code placed in file_start_write() and file_end_write()?
That makes more sense to me than sprinkling it in the aio code.
-ben
> Reported-by: Dmitry Monakhov <dmonakhov@xxxxxxxxxx>
> Signed-off-by: Jan Kara <jack@xxxxxxx>
> ---
> fs/aio.c | 31 ++++++++++++++++++++++++++++---
> include/linux/fs.h | 1 +
> 2 files changed, 29 insertions(+), 3 deletions(-)
>
> This patch seems to have fallen through the cracks. Al / Ben, can you please
> merge it? Thanks!
>
> diff --git a/fs/aio.c b/fs/aio.c
> index 155f84253f33..ee0871cb4677 100644
> --- a/fs/aio.c
> +++ b/fs/aio.c
> @@ -1065,6 +1065,19 @@ static void aio_complete(struct kiocb *kiocb, long res, long res2)
> unsigned tail, pos, head;
> unsigned long flags;
>
> + if (kiocb->ki_flags & IOCB_WRITE) {
> + struct file *f = kiocb->ki_filp;
> +
> + /*
> + * Tell lockdep we inherited freeze protection from submission
> + * thread.
> + */
> + percpu_rwsem_acquire(
> + &f->f_inode->i_sb->s_writers.rw_sem[SB_FREEZE_WRITE-1],
> + 1, _THIS_IP_);
> + file_end_write(f);
> + }
> +
> /*
> * Special case handling for sync iocbs:
> * - events go directly into the iocb for fast handling
> @@ -1449,13 +1462,25 @@ rw_common:
>
> len = ret;
>
> - if (rw == WRITE)
> + if (rw == WRITE) {
> file_start_write(file);
> + req->ki_flags |= IOCB_WRITE;
> + }
>
> ret = iter_op(req, &iter);
>
> - if (rw == WRITE)
> - file_end_write(file);
> + if (rw == WRITE) {
> + /*
> + * We release freeze protection in aio_complete(). Fool
> + * lockdep by telling it the lock got released so that
> + * it doesn't complain about held lock when we return
> + * to userspace.
> + */
> + percpu_rwsem_release(
> + &file->f_inode->i_sb->s_writers.rw_sem[SB_FREEZE_WRITE-1],
> + 1, _THIS_IP_);
> + }
> +
> kfree(iovec);
> break;
>
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index 3aa514254161..54af40ed6a26 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -319,6 +319,7 @@ struct writeback_control;
> #define IOCB_EVENTFD (1 << 0)
> #define IOCB_APPEND (1 << 1)
> #define IOCB_DIRECT (1 << 2)
> +#define IOCB_WRITE (1 << 3)
>
> struct kiocb {
> struct file *ki_filp;
> --
> 2.6.2
--
"Thought is the essence of where you are now."
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