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Message-ID: <a0d0fa88-e67c-4b35-88b4-74c5b15a16bb@gmx.com>
Date: Fri, 13 Sep 2024 07:02:31 +0930
From: Qu Wenruo <quwenruo.btrfs@....com>
To: Johannes Thumshirn <jth@...nel.org>, Chris Mason <clm@...com>,
Josef Bacik <josef@...icpanda.com>, David Sterba <dsterba@...e.com>,
"open list:BTRFS FILE SYSTEM" <linux-btrfs@...r.kernel.org>,
open list <linux-kernel@...r.kernel.org>
Cc: Johannes Thumshirn <johannes.thumshirn@....com>, Qu Wenru <wqu@...e.com>
Subject: Re: [PATCH] btrfs: scrub: skip PREALLOC extents on RAID stripe-tree
在 2024/9/13 00:03, Johannes Thumshirn 写道:
> From: Johannes Thumshirn <johannes.thumshirn@....com>
>
> When scrubbing a RAID stripe-tree based filesystem with preallocated
> extents, the btrfs_map_block() called by
> scrub_submit_extent_sector_read() will return ENOENT, because there is
> no RAID stripe-tree entry for preallocated extents. This then causes
> the sector to be marked as a sector with an I/O error.
>
> To prevent this false alert don't mark secotors for that
> btrfs_map_block() returned an ENOENT as I/O errors but skip them.
>
> This results for example in errors in fstests' btrfs/060 .. btrfs/074
> which all perform fsstress and scrub operations. Whit this fix, these
> errors are gone and the tests pass again.
>
> Cc: Qu Wenru <wqu@...e.com>
My concern is, ENOENT can be some real problems other than PREALLOC.
I'd prefer this to be the last-resort method.
Would it be possible to create an RST entry for preallocated operations
manually? E.g. without creating a dummy OE, but just insert the needed
RST entries into RST tree at fallocate time?
Thanks,
Qu
> Signed-off-by: Johannes Thumshirn <johannes.thumshirn@....com>
> ---
> fs/btrfs/scrub.c | 15 +++++++++++++--
> 1 file changed, 13 insertions(+), 2 deletions(-)
>
> diff --git a/fs/btrfs/scrub.c b/fs/btrfs/scrub.c
> index 3a3427428074..b195c41676e3 100644
> --- a/fs/btrfs/scrub.c
> +++ b/fs/btrfs/scrub.c
> @@ -1657,7 +1657,7 @@ static u32 stripe_length(const struct scrub_stripe *stripe)
> }
>
> static void scrub_submit_extent_sector_read(struct scrub_ctx *sctx,
> - struct scrub_stripe *stripe)
> + struct scrub_stripe *stripe)
> {
> struct btrfs_fs_info *fs_info = stripe->bg->fs_info;
> struct btrfs_bio *bbio = NULL;
> @@ -1703,10 +1703,21 @@ static void scrub_submit_extent_sector_read(struct scrub_ctx *sctx,
> err = btrfs_map_block(fs_info, BTRFS_MAP_READ, logical,
> &stripe_len, &bioc, &io_stripe, &mirror);
> btrfs_put_bioc(bioc);
> - if (err < 0) {
> + if (err < 0 && err != -ENOENT) {
> set_bit(i, &stripe->io_error_bitmap);
> set_bit(i, &stripe->error_bitmap);
> continue;
> + } else if (err == -ENOENT) {
> + /*
> + * btrfs_map_block() returns -ENOENT if it can't
> + * find the logical address in the RAID stripe
> + * tree. This can happens on PREALLOC extents.
> + * As we know the extent tree has an extent
> + * recorded there, we can be sure this is a
> + * PREALLOC extent, so skip this sector and
> + * continue to the next.
> + */
> + continue;
> }
>
> bbio = btrfs_bio_alloc(stripe->nr_sectors, REQ_OP_READ,
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