Re: Block layer projects that I haven't had time for

[Ming Lin]

On Thu, Dec 11, 2014 at 2:07 AM, Dongsu Park
<dongsu.park@xxxxxxxxxxxxxxxx> wrote:
> Hi Ming & Kent,
>
> On 10.12.2014 23:11, Ming Lin wrote:
>> > On Wed, Dec 10, 2014 at 02:42:14PM -0800, Ming Lin wrote:
>> > Try this fix:
>> Yes, it fixed ext4 problem.
>
> @kent: Thank you for the patch. Indeed it fixes the ext4 lockup I've seen.
> I've applied it to my tree, under the branch block-mpage-bvecs-for-next.
> See 0d2e05525a58 ("fs/ext4: fix a lockup when writing blocks into ext4
> rootfs") <https://github.com/dongsupark/linux/commit/0d2e05525a58>.
>
> After that of course, more bugs start to appear, e.g. crash with virtio-blk,
> like we'd have opened a can of worms. ;-)
>
>> Just tried to edit a btrfs file.
>>
>> [   45.216351] BTRFS error (device sdb1): partial page write in btrfs with
>> offset 0 and length 8192
>> [   45.217522] BTRFS critical (device sdb1): bad ordered accounting left 0
>> size 4096
>
> @ming: I guess you managed to see this error as you're testing with a
> SCSI device, not virtio-blk device like me.
> Are you seeing it without any back traces?
> Does the attached patch fix your issue?
> (This is already included in the branch block-mpage-bvecs-for-next.)

Hi Dongsu,

Yes, I'm testing with a SCSI device.
Tested your latest block-mpage-bvecs-for-next.
Same problem with BTRFS and no any back traces.

Thanks,
Ming

>
> Thanks,
> Dongsu
>
> ====
>
> From 7cef37e357b4fd636b3d4aa296e8b67ba8db66d1 Mon Sep 17 00:00:00 2001
> From: Dongsu Park <dongsu.park@xxxxxxxxxxxxxxxx>
> Date: Tue, 9 Dec 2014 18:10:10 +0100
> Subject: [PATCH] btrfs: use a correct function for bvec iteration in
>  btrfs_csum_one_bio()
>
> Commit 94607a8a("block: Convert various code to bio_for_each_page()")
> introduced a critical bug in btrfs_csum_one_bio() using
> bio_for_each_page_all() for iterating through each bvec.
> That should actually call bio_for_each_page() to take the current
> offset into account. Without this fix, xfstests/btrfs/012 would
> end up with lockup with warnings in btrfs_add_ordered_sum(), because
> iter.bi_size becomes < 0.
>
> Signed-off-by: Dongsu Park <dongsu.park@xxxxxxxxxxxxxxxx>
> ---
>  fs/btrfs/file-item.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/fs/btrfs/file-item.c b/fs/btrfs/file-item.c
> index 6a81176..c7ae23c 100644
> --- a/fs/btrfs/file-item.c
> +++ b/fs/btrfs/file-item.c
> @@ -447,7 +447,7 @@ int btrfs_csum_one_bio(struct btrfs_root *root, struct inode *inode,
>         sums->bytenr = (u64)bio->bi_iter.bi_sector << 9;
>         index = 0;
>
> -       bio_for_each_page_all(bvec, bio, iter) {
> +       bio_for_each_page(bvec, bio, iter) {
>                 if (!contig)
>                         offset = page_offset(bvec.bv_page) + bvec.bv_offset;
>
> --
> 1.9.3
>
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