[PATCH 004 of 5] md: Improve detection of lack of barrier support in raid1
From: NeilBrown <hidden>
Date: 2006-04-28 02:52:13
Also in:
lkml
Move the test for 'do barrier work' down a bit so that if the first write to a raid1 is a BIO_RW_BARRIER write, the checking done by superblock writes will cause the right thing to happen. Signed-off-by: Neil Brown <redacted> ### Diffstat output ./drivers/md/raid1.c | 16 +++++++++++----- 1 file changed, 11 insertions(+), 5 deletions(-) diff ./drivers/md/raid1.c~current~ ./drivers/md/raid1.c
--- ./drivers/md/raid1.c~current~ 2006-04-28 12:17:27.000000000 +1000
+++ ./drivers/md/raid1.c 2006-04-28 12:17:40.000000000 +1000@@ -753,18 +753,24 @@ static int make_request(request_queue_t const int rw = bio_data_dir(bio); int do_barriers; - if (unlikely(!mddev->barriers_work && bio_barrier(bio))) { - bio_endio(bio, bio->bi_size, -EOPNOTSUPP); - return 0; - } - /* * Register the new request and wait if the reconstruction * thread has put up a bar for new requests. * Continue immediately if no resync is active currently. + * We test barriers_work *after* md_write_start as md_write_start + * may cause the first superblock write, and that will check out + * if barriers work. */ + md_write_start(mddev, bio); /* wait on superblock update early */ + if (unlikely(!mddev->barriers_work && bio_barrier(bio))) { + if (rw == WRITE) + md_write_end(mddev); + bio_endio(bio, bio->bi_size, -EOPNOTSUPP); + return 0; + } + wait_barrier(conf); disk_stat_inc(mddev->gendisk, ios[rw]);