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authorNeilBrown <neilb@cse.unsw.edu.au>2005-06-21 17:17:12 -0700
committerLinus Torvalds <torvalds@ppc970.osdl.org>2005-06-21 19:07:43 -0700
commit06d91a5fe0b50c9060e70bdf7786f8a3c66249db (patch)
tree95a8b9228534cebb12eb31c1cc9cc0c45f685410 /drivers/md/md.c
parentfca4d848f0e6fafdc2b25f8a0cf1e76935f13ac2 (diff)
downloadlwn-06d91a5fe0b50c9060e70bdf7786f8a3c66249db.tar.gz
lwn-06d91a5fe0b50c9060e70bdf7786f8a3c66249db.zip
[PATCH] md: improve locking on 'safemode' and move superblock writes
When md marks the superblock dirty before a write, it calls generic_make_request (to write the superblock) from within generic_make_request (to write the first dirty block), which could cause problems later. With this patch, the superblock write is always done by the helper thread, and write request are delayed until that write completes. Also, the locking around marking the array dirty and writing the superblock is improved to avoid possible races. Signed-off-by: Neil Brown <neilb@cse.unsw.edu.au> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'drivers/md/md.c')
-rw-r--r--drivers/md/md.c73
1 files changed, 59 insertions, 14 deletions
diff --git a/drivers/md/md.c b/drivers/md/md.c
index c842e34d850e..177d2a7d7cea 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -218,6 +218,8 @@ static mddev_t * mddev_find(dev_t unit)
INIT_LIST_HEAD(&new->all_mddevs);
init_timer(&new->safemode_timer);
atomic_set(&new->active, 1);
+ bio_list_init(&new->write_list);
+ spin_lock_init(&new->write_lock);
new->queue = blk_alloc_queue(GFP_KERNEL);
if (!new->queue) {
@@ -1251,9 +1253,11 @@ static void md_update_sb(mddev_t * mddev)
int err, count = 100;
struct list_head *tmp;
mdk_rdev_t *rdev;
+ int sync_req;
- mddev->sb_dirty = 0;
repeat:
+ spin_lock(&mddev->write_lock);
+ sync_req = mddev->in_sync;
mddev->utime = get_seconds();
mddev->events ++;
@@ -1272,8 +1276,12 @@ repeat:
* do not write anything to disk if using
* nonpersistent superblocks
*/
- if (!mddev->persistent)
+ if (!mddev->persistent) {
+ mddev->sb_dirty = 0;
+ spin_unlock(&mddev->write_lock);
return;
+ }
+ spin_unlock(&mddev->write_lock);
dprintk(KERN_INFO
"md: updating %s RAID superblock on device (in sync %d)\n",
@@ -1304,6 +1312,15 @@ repeat:
printk(KERN_ERR \
"md: excessive errors occurred during superblock update, exiting\n");
}
+ spin_lock(&mddev->write_lock);
+ if (mddev->in_sync != sync_req) {
+ /* have to write it out again */
+ spin_unlock(&mddev->write_lock);
+ goto repeat;
+ }
+ mddev->sb_dirty = 0;
+ spin_unlock(&mddev->write_lock);
+
}
/*
@@ -3178,19 +3195,31 @@ void md_done_sync(mddev_t *mddev, int blocks, int ok)
}
-void md_write_start(mddev_t *mddev)
+/* md_write_start(mddev, bi)
+ * If we need to update some array metadata (e.g. 'active' flag
+ * in superblock) before writing, queue bi for later writing
+ * and return 0, else return 1 and it will be written now
+ */
+int md_write_start(mddev_t *mddev, struct bio *bi)
{
- if (!atomic_read(&mddev->writes_pending)) {
- mddev_lock_uninterruptible(mddev);
- if (mddev->in_sync) {
- mddev->in_sync = 0;
- del_timer(&mddev->safemode_timer);
- md_update_sb(mddev);
- }
- atomic_inc(&mddev->writes_pending);
- mddev_unlock(mddev);
- } else
- atomic_inc(&mddev->writes_pending);
+ if (bio_data_dir(bi) != WRITE)
+ return 1;
+
+ atomic_inc(&mddev->writes_pending);
+ spin_lock(&mddev->write_lock);
+ if (mddev->in_sync == 0 && mddev->sb_dirty == 0) {
+ spin_unlock(&mddev->write_lock);
+ return 1;
+ }
+ bio_list_add(&mddev->write_list, bi);
+
+ if (mddev->in_sync) {
+ mddev->in_sync = 0;
+ mddev->sb_dirty = 1;
+ }
+ spin_unlock(&mddev->write_lock);
+ md_wakeup_thread(mddev->thread);
+ return 0;
}
void md_write_end(mddev_t *mddev)
@@ -3472,6 +3501,7 @@ void md_check_recovery(mddev_t *mddev)
mddev->sb_dirty ||
test_bit(MD_RECOVERY_NEEDED, &mddev->recovery) ||
test_bit(MD_RECOVERY_DONE, &mddev->recovery) ||
+ mddev->write_list.head ||
(mddev->safemode == 1) ||
(mddev->safemode == 2 && ! atomic_read(&mddev->writes_pending)
&& !mddev->in_sync && mddev->recovery_cp == MaxSector)
@@ -3480,7 +3510,9 @@ void md_check_recovery(mddev_t *mddev)
if (mddev_trylock(mddev)==0) {
int spares =0;
+ struct bio *blist;
+ spin_lock(&mddev->write_lock);
if (mddev->safemode && !atomic_read(&mddev->writes_pending) &&
!mddev->in_sync && mddev->recovery_cp == MaxSector) {
mddev->in_sync = 1;
@@ -3488,9 +3520,22 @@ void md_check_recovery(mddev_t *mddev)
}
if (mddev->safemode == 1)
mddev->safemode = 0;
+ blist = bio_list_get(&mddev->write_list);
+ spin_unlock(&mddev->write_lock);
if (mddev->sb_dirty)
md_update_sb(mddev);
+
+ while (blist) {
+ struct bio *b = blist;
+ blist = blist->bi_next;
+ b->bi_next = NULL;
+ generic_make_request(b);
+ /* we already counted this, so need to un-count */
+ md_write_end(mddev);
+ }
+
+
if (test_bit(MD_RECOVERY_RUNNING, &mddev->recovery) &&
!test_bit(MD_RECOVERY_DONE, &mddev->recovery)) {
/* resync/recovery still happening */