kernel/git/stable/linux.git/drivers/md/raid10.c, branch linux-2.6.25.y

md: Ensure interrupted recovery completed properly (v1 metadata plus bitmap)

2008-07-24T16:14:03+00:00

commit 8c2e870a625bd336b2e7a65a97c1836acef07322 upstream If, while assembling an array, we find a device which is not fully in-sync with the array, it is important to set the "fullsync" flags. This is an exact analog to the setting of this flag in hot_add_disk methods. Currently, only v1.x metadata supports having devices in an array which are not fully in-sync (it keep track of how in sync they are). The 'fullsync' flag only makes a difference when a write-intent bitmap is being used. In this case it tells recovery to ignore the bitmap and recovery all blocks. This fix is already in place for raid1, but not raid5/6 or raid10. So without this fix, a raid1 ir raid4/5/6 array with version 1.x metadata and a write intent bitmaps, that is stopped in the middle of a recovery, will appear to complete the recovery instantly after it is reassembled, but the recovery will not be correct. If you might have an array like that, issueing echo repair > /sys/block/mdXX/md/sync_action will make sure recovery completes properly. Signed-off-by: Neil Brown Signed-off-by: Greg Kroah-Hartman

md: the md RAID10 resync thread could cause a md RAID10 array deadlock

2008-03-05T00:35:18+00:00

This message describes another issue about md RAID10 found by testing the 2.6.24 md RAID10 using new scsi fault injection framework. Abstract: When a scsi error results in disabling a disk during RAID10 recovery, the resync threads of md RAID10 could stall. This case, the raid array has already been broken and it may not matter. But I think stall is not preferable. If it occurs, even shutdown or reboot will fail because of resource busy. The deadlock mechanism: The r10bio_s structure has a "remaining" member to keep track of BIOs yet to be handled when recovering. The "remaining" counter is incremented when building a BIO in sync_request() and is decremented when finish a BIO in end_sync_write(). If building a BIO fails for some reasons in sync_request(), the "remaining" should be decremented if it has already been incremented. I found a case where this decrement is forgotten. This causes a md_do_sync() deadlock because md_do_sync() waits for md_done_sync() called by end_sync_write(), but end_sync_write() never calls md_done_sync() because of the "remaining" counter mismatch. For example, this problem would be reproduced in the following case: Personalities : [raid10] md0 : active raid10 sdf1[4] sde1[5](F) sdd1[2] sdc1[1] sdb1[6](F) 3919616 blocks 64K chunks 2 near-copies [4/2] [_UU_] [>....................] recovery = 2.2% (45376/1959808) finish=0.7min speed=45376K/sec This case, sdf1 is recovering, sdb1 and sde1 are disabled. An additional error with detaching sdd will cause a deadlock. md0 : active raid10 sdf1[4] sde1[5](F) sdd1[6](F) sdc1[1] sdb1[7](F) 3919616 blocks 64K chunks 2 near-copies [4/1] [_U__] [=>...................] recovery = 5.0% (99520/1959808) finish=5.9min speed=5237K/sec 2739 ? S< 0:17 [md0_raid10] 28608 ? D< 0:00 [md0_resync] 28629 pts/1 Ss 0:00 bash 28830 pts/1 R+ 0:00 ps ax 31819 ? D< 0:00 [kjournald] The resync thread keeps working, but actually it is deadlocked. Patch: By this patch, the remaining counter will be decremented if needed. Signed-off-by: Neil Brown Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

md: fix possible raid1/raid10 deadlock on read error during resync

2008-03-05T00:35:18+00:00

Thanks to K.Tanaka and the scsi fault injection framework, here is a fix for another possible deadlock in raid1/raid10 error handing. If a read request returns an error while a resync is happening and a resync request is pending, the attempt to fix the error will block until the resync progresses, and the resync will block until the read request completes. Thus a deadlock. This patch fixes the problem. Cc: "K.Tanaka" Signed-off-by: Neil Brown Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

md: don't attempt read-balancing for raid10 'far' layouts

2008-03-05T00:35:18+00:00

This patch changes the disk to be read for layout "far > 1" to always be the disk with the lowest block address. Thus the chunks to be read will always be (for a fully functioning array) from the first band of stripes, and the raid will then work as a raid0 consisting of the first band of stripes. Some advantages: The fastest part which is the outer sectors of the disks involved will be used. The outer blocks of a disk may be as much as 100 % faster than the inner blocks. Average seek time will be smaller, as seeks will always be confined to the first part of the disks. Mixed disks with different performance characteristics will work better, as they will work as raid0, the sequential read rate will be number of disks involved times the IO rate of the slowest disk. If a disk is malfunctioning, the first disk which is working, and has the lowest block address for the logical block will be used. Signed-off-by: Keld Simonsen Signed-off-by: Neil Brown Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

md: fix deadlock in md/raid1 and md/raid10 when handling a read error

2008-03-05T00:35:17+00:00

When handling a read error, we freeze the array to stop any other IO while attempting to over-write with correct data. This is done in the raid1d(raid10d) thread and must wait for all submitted IO to complete (except for requests that failed and are sitting in the retry queue - these are counted in ->nr_queue and will stay there during a freeze). However write requests need attention from raid1d as bitmap updates might be required. This can cause a deadlock as raid1 is waiting for requests to finish that themselves need attention from raid1d. So we create a new function 'flush_pending_writes' to give that attention, and call it in freeze_array to be sure that we aren't waiting on raid1d. Thanks to "K.Tanaka" for finding and reporting this problem. Cc: "K.Tanaka" Signed-off-by: Neil Brown Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

md: change ITERATE_RDEV to rdev_for_each

2008-02-06T18:41:19+00:00

As this is more in line with common practice in the kernel. Also swap the args around to be more like list_for_each. Signed-off-by: Neil Brown Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

md: allow a maximum extent to be set for resyncing

2008-02-06T18:41:18+00:00

This allows userspace to control resync/reshape progress and synchronise it with other activities, such as shared access in a SAN, or backing up critical sections during a tricky reshape. Writing a number of sectors (which must be a multiple of the chunk size if such is meaningful) causes a resync to pause when it gets to that point. Signed-off-by: Neil Brown Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

md: Update md bitmap during resync.

2008-02-06T18:41:18+00:00

Currently an md array with a write-intent bitmap does not updated that bitmap to reflect successful partial resync. Rather the entire bitmap is updated when the resync completes. This is because there is no guarentee that resync requests will complete in order, and tracking each request individually is unnecessarily burdensome. However there is value in regularly updating the bitmap, so add code to periodically pause while all pending sync requests complete, then update the bitmap. Doing this only every few seconds (the same as the bitmap update time) does not notciably affect resync performance. [snitzer@gmail.com: export bitmap_cond_end_sync] Signed-off-by: Neil Brown Cc: "Mike Snitzer" Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

Add UNPLUG traces to all appropriate places

2007-11-09T12:41:32+00:00

Added blk_unplug interface, allowing all invocations of unplugs to result in a generated blktrace UNPLUG. Signed-off-by: Alan D. Brunelle Signed-off-by: Jens Axboe

block: convert blkdev_issue_flush() to use empty barriers

2007-10-16T09:05:02+00:00

Then we can get rid of ->issue_flush_fn() and all the driver private implementations of that. Signed-off-by: Jens Axboe