On Fri, Mar 02, 2018 at 04:10:37PM -0700, Liu Bo wrote:
> In case of raid56, writes and rebuilds always take BTRFS_STRIPE_LEN(64K)
> as unit, however, scrub_extent() sets blocksize as unit, so rebuild
> process may be triggered on every block on a same stripe.
>
> A typical example would be that when we're replacing a disappeared disk,
> all reads on the disks get -EIO, every block (size is 4K if blocksize is
> 4K) would go thru these,
>
> scrub_handle_errored_block
> scrub_recheck_block # re-read pages one by one
> scrub_recheck_block # rebuild by calling raid56_parity_recover()
> page by page
>
> Although with raid56 stripe cache most of reads during rebuild can be
> avoided, the parity recover calculation(xor or raid6 algorithms) needs to
> be done $(BTRFS_STRIPE_LEN / blocksize) times.
>
> This makes it less stupid by doing raid56 scrub/replace on stripe length.
missing s-o-b
> ---
> fs/btrfs/scrub.c | 78
> +++++++++++++++++++++++++++++++++++++++++++-------------
> 1 file changed, 60 insertions(+), 18 deletions(-)
>
> diff --git a/fs/btrfs/scrub.c b/fs/btrfs/scrub.c
> index 9882513..e3203a1 100644
> --- a/fs/btrfs/scrub.c
> +++ b/fs/btrfs/scrub.c
> @@ -1718,6 +1718,44 @@ static int scrub_submit_raid56_bio_wait(struct
> btrfs_fs_info *fs_info,
> return blk_status_to_errno(bio->bi_status);
> }
>
> +static void scrub_recheck_block_on_raid56(struct btrfs_fs_info *fs_info,
> + struct scrub_block *sblock)
> +{
> + struct scrub_page *first_page = sblock->pagev[0];
> + struct bio *bio = btrfs_io_bio_alloc(BIO_MAX_PAGES);
nontrivial initializations (variable to variable) are better put into
the statement section.
> + int page_num;
> +
> + /* All pages in sblock belongs to the same stripe on the same device. */
> + ASSERT(first_page->dev);
> + if (first_page->dev->bdev == NULL)
> + goto out;
> +
> + bio_set_dev(bio, first_page->dev->bdev);
> +
> + for (page_num = 0; page_num < sblock->page_count; page_num++) {
> + struct scrub_page *page = sblock->pagev[page_num];
> +
> + WARN_ON(!page->page);
> + bio_add_page(bio, page->page, PAGE_SIZE, 0);
> + }
> +
> + if (scrub_submit_raid56_bio_wait(fs_info, bio, first_page)) {
> + bio_put(bio);
> + goto out;
> + }
> +
> + bio_put(bio);
> +
> + scrub_recheck_block_checksum(sblock);
> +
> + return;
> +out:
> + for (page_num = 0; page_num < sblock->page_count; page_num++)
> + sblock->pagev[page_num]->io_error = 1;
> +
> + sblock->no_io_error_seen = 0;
> +}
> +
> /*
> * this function will check the on disk data for checksum errors, header
> * errors and read I/O errors. If any I/O errors happen, the exact pages
> @@ -1733,6 +1771,10 @@ static void scrub_recheck_block(struct btrfs_fs_info
> *fs_info,
>
> sblock->no_io_error_seen = 1;
>
> + /* short cut for raid56 */
> + if (!retry_failed_mirror && scrub_is_page_on_raid56(sblock->pagev[0]))
> + return scrub_recheck_block_on_raid56(fs_info, sblock);
> +
> for (page_num = 0; page_num < sblock->page_count; page_num++) {
> struct bio *bio;
> struct scrub_page *page = sblock->pagev[page_num];
> @@ -1748,19 +1790,12 @@ static void scrub_recheck_block(struct btrfs_fs_info
> *fs_info,
> bio_set_dev(bio, page->dev->bdev);
>
> bio_add_page(bio, page->page, PAGE_SIZE, 0);
> - if (!retry_failed_mirror && scrub_is_page_on_raid56(page)) {
> - if (scrub_submit_raid56_bio_wait(fs_info, bio, page)) {
> - page->io_error = 1;
> - sblock->no_io_error_seen = 0;
> - }
> - } else {
> - bio->bi_iter.bi_sector = page->physical >> 9;
> - bio_set_op_attrs(bio, REQ_OP_READ, 0);
> + bio->bi_iter.bi_sector = page->physical >> 9;
> + bio_set_op_attrs(bio, REQ_OP_READ, 0);
https://elixir.bootlin.com/linux/latest/source/include/linux/blk_types.h#L270
bio_set_op_attrs should not be used
>
> - if (btrfsic_submit_bio_wait(bio)) {
> - page->io_error = 1;
> - sblock->no_io_error_seen = 0;
> - }
> + if (btrfsic_submit_bio_wait(bio)) {
> + page->io_error = 1;
> + sblock->no_io_error_seen = 0;
> }
>
> bio_put(bio);
> @@ -2728,7 +2763,8 @@ static int scrub_find_csum(struct scrub_ctx *sctx, u64
> logical, u8 *csum)
> }
>
> /* scrub extent tries to collect up to 64 kB for each bio */
> -static int scrub_extent(struct scrub_ctx *sctx, u64 logical, u64 len,
> +static int scrub_extent(struct scrub_ctx *sctx, struct map_lookup *map,
> + u64 logical, u64 len,
> u64 physical, struct btrfs_device *dev, u64 flags,
> u64 gen, int mirror_num, u64 physical_for_dev_replace)
> {
> @@ -2737,13 +2773,19 @@ static int scrub_extent(struct scrub_ctx *sctx, u64
> logical, u64 len,
> u32 blocksize;
>
> if (flags & BTRFS_EXTENT_FLAG_DATA) {
> - blocksize = sctx->fs_info->sectorsize;
> + if (map->type & BTRFS_BLOCK_GROUP_RAID56_MASK)
> + blocksize = map->stripe_len;
> + else
> + blocksize = sctx->fs_info->sectorsize;
> spin_lock(&sctx->stat_lock);
> sctx->stat.data_extents_scrubbed++;
> sctx->stat.data_bytes_scrubbed += len;
> spin_unlock(&sctx->stat_lock);
> } else if (flags & BTRFS_EXTENT_FLAG_TREE_BLOCK) {
> - blocksize = sctx->fs_info->nodesize;
> + if (map->type & BTRFS_BLOCK_GROUP_RAID56_MASK)
> + blocksize = map->stripe_len;
> + else
> + blocksize = sctx->fs_info->nodesize;
> spin_lock(&sctx->stat_lock);
> sctx->stat.tree_extents_scrubbed++;
> sctx->stat.tree_bytes_scrubbed += len;
> @@ -2883,9 +2925,9 @@ static int scrub_extent_for_parity(struct scrub_parity
> *sparity,
> }
>
> if (flags & BTRFS_EXTENT_FLAG_DATA) {
> - blocksize = sctx->fs_info->sectorsize;
> + blocksize = sparity->stripe_len;
> } else if (flags & BTRFS_EXTENT_FLAG_TREE_BLOCK) {
> - blocksize = sctx->fs_info->nodesize;
> + blocksize = sparity->stripe_len;
> } else {
> blocksize = sctx->fs_info->sectorsize;
> WARN_ON(1);
> @@ -3595,7 +3637,7 @@ static noinline_for_stack int scrub_stripe(struct
> scrub_ctx *sctx,
> if (ret)
> goto out;
>
> - ret = scrub_extent(sctx, extent_logical, extent_len,
> + ret = scrub_extent(sctx, map, extent_logical,
> extent_len,
> extent_physical, extent_dev, flags,
> generation, extent_mirror_num,
> extent_logical - logical + physical);
> --
> 2.9.4
>
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