Using wait_for_completion() for waiting for a IO request to be executed results in wrong iowait time accounting. For example, a system having the only task doing write() and fdatasync() on a block device can be reported being idle instead of iowaiting as it should because blkdev_issue_flush() calls wait_for_completion() which in turn calls schedule() that does not increment the iowait proc counter and thus does not turn on iowait time accounting.
The patch makes block layer use wait_for_completion_io() instead of wait_for_completion() where appropriate to account iowait time correctly. Signed-off-by: Vladimir Davydov <[email protected]> --- block/blk-exec.c | 4 ++-- block/blk-flush.c | 2 +- block/blk-lib.c | 6 +++--- 3 files changed, 6 insertions(+), 6 deletions(-) diff --git a/block/blk-exec.c b/block/blk-exec.c index 74638ec..f634de7 100644 --- a/block/blk-exec.c +++ b/block/blk-exec.c @@ -120,9 +120,9 @@ int blk_execute_rq(struct request_queue *q, struct gendisk *bd_disk, /* Prevent hang_check timer from firing at us during very long I/O */ hang_check = sysctl_hung_task_timeout_secs; if (hang_check) - while (!wait_for_completion_timeout(&wait, hang_check * (HZ/2))); + while (!wait_for_completion_io_timeout(&wait, hang_check * (HZ/2))); else - wait_for_completion(&wait); + wait_for_completion_io(&wait); if (rq->errors) err = -EIO; diff --git a/block/blk-flush.c b/block/blk-flush.c index 720ad60..db8f1b5 100644 --- a/block/blk-flush.c +++ b/block/blk-flush.c @@ -436,7 +436,7 @@ int blkdev_issue_flush(struct block_device *bdev, gfp_t gfp_mask, bio_get(bio); submit_bio(WRITE_FLUSH, bio); - wait_for_completion(&wait); + wait_for_completion_io(&wait); /* * The driver must store the error location in ->bi_sector, if diff --git a/block/blk-lib.c b/block/blk-lib.c index b3a1f2b..d6f50d5 100644 --- a/block/blk-lib.c +++ b/block/blk-lib.c @@ -126,7 +126,7 @@ int blkdev_issue_discard(struct block_device *bdev, sector_t sector, /* Wait for bios in-flight */ if (!atomic_dec_and_test(&bb.done)) - wait_for_completion(&wait); + wait_for_completion_io(&wait); if (!test_bit(BIO_UPTODATE, &bb.flags)) ret = -EIO; @@ -200,7 +200,7 @@ int blkdev_issue_write_same(struct block_device *bdev, sector_t sector, /* Wait for bios in-flight */ if (!atomic_dec_and_test(&bb.done)) - wait_for_completion(&wait); + wait_for_completion_io(&wait); if (!test_bit(BIO_UPTODATE, &bb.flags)) ret = -ENOTSUPP; @@ -262,7 +262,7 @@ int __blkdev_issue_zeroout(struct block_device *bdev, sector_t sector, /* Wait for bios in-flight */ if (!atomic_dec_and_test(&bb.done)) - wait_for_completion(&wait); + wait_for_completion_io(&wait); if (!test_bit(BIO_UPTODATE, &bb.flags)) /* One of bios in the batch was completed with error.*/ -- 1.7.1 _______________________________________________ Devel mailing list [email protected] https://lists.openvz.org/mailman/listinfo/devel
