Btrfs: scrub: batch rebuild for raid56

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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 smarter by doing raid56 scrub/replace on stripe length.

Signed-off-by: Liu Bo <bo.li.liu@oracle.com>
Signed-off-by: David Sterba <dsterba@suse.com>

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This commit is contained in:

Liu Bo 2018-03-07 12:08:09 -07:00 • committed by David Sterba

parent 416a72022e

commit 6ca1765b36

1 changed files with 61 additions and 18 deletions

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fs/btrfs/scrub.c

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