btrfs: reada: avoid undone reada extents in btrfs_reada_wait

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Reada background works is not designed to finish all jobs
completely, it will break in following case:
1: When a device reaches workload limit (MAX_IN_FLIGHT)
2: Total reads reach max limit (10000)
3: All devices don't have queued more jobs, often happened in DUP case

And if all background works exit with remaining jobs,
btrfs_reada_wait() will wait indefinetelly.

Above problem is rarely happened in old code, because:
1: Every work queues 2x new works
   So many works reduced chances of undone jobs.
2: One work will continue 10000 times loop in case of no-jobs
   It reduced no-thread window time.

But after we fixed above case, the "undone reada extents" frequently
happened.

Fix:
 Check to ensure we have at least one thread if there are undone jobs
 in btrfs_reada_wait().

Signed-off-by: Zhao Lei <zhaolei@cn.fujitsu.com>
Signed-off-by: David Sterba <dsterba@suse.com>

...

This commit is contained in:

Zhao Lei 2016-01-26 18:42:40 +08:00 • committed by David Sterba

parent 2fefd5583f

commit 4fe7a0e138

1 changed files with 8 additions and 1 deletions

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