[PATCH] md: support write-mostly device in raid1
This allows a device in a raid1 to be marked as "write mostly". Read requests will only be sent if there is no other option. 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>
This commit is contained in:
NeilBrown
Linus Torvalds
Родитель
36fa30636f
Коммит
8ddf9efe67
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@ -670,6 +670,7 @@ static int super_90_validate(mddev_t *mddev, mdk_rdev_t *rdev)
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if (mddev->level != LEVEL_MULTIPATH) {
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rdev->faulty = 0;
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rdev->flags = 0;
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desc = sb->disks + rdev->desc_nr;
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if (desc->state & (1<<MD_DISK_FAULTY))
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@ -679,6 +680,8 @@ static int super_90_validate(mddev_t *mddev, mdk_rdev_t *rdev)
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rdev->in_sync = 1;
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rdev->raid_disk = desc->raid_disk;
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}
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if (desc->state & (1<<MD_DISK_WRITEMOSTLY))
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set_bit(WriteMostly, &rdev->flags);
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} else /* MULTIPATH are always insync */
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rdev->in_sync = 1;
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return 0;
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@ -777,6 +780,8 @@ static void super_90_sync(mddev_t *mddev, mdk_rdev_t *rdev)
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spare++;
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working++;
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}
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if (test_bit(WriteMostly, &rdev2->flags))
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d->state |= (1<<MD_DISK_WRITEMOSTLY);
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}
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/* now set the "removed" and "faulty" bits on any missing devices */
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@ -990,6 +995,9 @@ static int super_1_validate(mddev_t *mddev, mdk_rdev_t *rdev)
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rdev->raid_disk = role;
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break;
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}
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rdev->flags = 0;
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if (sb->devflags & WriteMostly1)
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set_bit(WriteMostly, &rdev->flags);
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} else /* MULTIPATH are always insync */
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rdev->in_sync = 1;
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@ -2152,6 +2160,8 @@ static int get_disk_info(mddev_t * mddev, void __user * arg)
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info.state |= (1<<MD_DISK_ACTIVE);
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info.state |= (1<<MD_DISK_SYNC);
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}
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if (test_bit(WriteMostly, &rdev->flags))
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info.state |= (1<<MD_DISK_WRITEMOSTLY);
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} else {
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info.major = info.minor = 0;
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info.raid_disk = -1;
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@ -2237,6 +2247,9 @@ static int add_new_disk(mddev_t * mddev, mdu_disk_info_t *info)
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rdev->saved_raid_disk = rdev->raid_disk;
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rdev->in_sync = 0; /* just to be sure */
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if (info->state & (1<<MD_DISK_WRITEMOSTLY))
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set_bit(WriteMostly, &rdev->flags);
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rdev->raid_disk = -1;
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err = bind_rdev_to_array(rdev, mddev);
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if (err)
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@ -2277,6 +2290,9 @@ static int add_new_disk(mddev_t * mddev, mdu_disk_info_t *info)
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else
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rdev->in_sync = 0;
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if (info->state & (1<<MD_DISK_WRITEMOSTLY))
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set_bit(WriteMostly, &rdev->flags);
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err = bind_rdev_to_array(rdev, mddev);
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if (err) {
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export_rdev(rdev);
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@ -3329,6 +3345,8 @@ static int md_seq_show(struct seq_file *seq, void *v)
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char b[BDEVNAME_SIZE];
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seq_printf(seq, " %s[%d]",
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bdevname(rdev->bdev,b), rdev->desc_nr);
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if (test_bit(WriteMostly, &rdev->flags))
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seq_printf(seq, "(W)");
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if (rdev->faulty) {
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seq_printf(seq, "(F)");
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continue;
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@ -360,13 +360,14 @@ static int read_balance(conf_t *conf, r1bio_t *r1_bio)
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{
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const unsigned long this_sector = r1_bio->sector;
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int new_disk = conf->last_used, disk = new_disk;
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int wonly_disk = -1;
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const int sectors = r1_bio->sectors;
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sector_t new_distance, current_distance;
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mdk_rdev_t *new_rdev, *rdev;
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mdk_rdev_t *rdev;
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rcu_read_lock();
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/*
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* Check if it if we can balance. We can balance on the whole
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* Check if we can balance. We can balance on the whole
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* device if no resync is going on, or below the resync window.
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* We take the first readable disk when above the resync window.
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*/
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@ -376,11 +377,16 @@ static int read_balance(conf_t *conf, r1bio_t *r1_bio)
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/* Choose the first operation device, for consistancy */
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new_disk = 0;
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while ((new_rdev=conf->mirrors[new_disk].rdev) == NULL ||
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!new_rdev->in_sync) {
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new_disk++;
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if (new_disk == conf->raid_disks) {
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new_disk = -1;
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for (rdev = conf->mirrors[new_disk].rdev;
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!rdev || !rdev->in_sync
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|| test_bit(WriteMostly, &rdev->flags);
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rdev = conf->mirrors[++new_disk].rdev) {
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if (rdev && rdev->in_sync)
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wonly_disk = new_disk;
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if (new_disk == conf->raid_disks - 1) {
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new_disk = wonly_disk;
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break;
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}
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}
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@ -389,16 +395,26 @@ static int read_balance(conf_t *conf, r1bio_t *r1_bio)
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/* make sure the disk is operational */
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while ((new_rdev=conf->mirrors[new_disk].rdev) == NULL ||
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!new_rdev->in_sync) {
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for (rdev = conf->mirrors[new_disk].rdev;
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!rdev || !rdev->in_sync ||
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test_bit(WriteMostly, &rdev->flags);
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rdev = conf->mirrors[new_disk].rdev) {
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if (rdev && rdev->in_sync)
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wonly_disk = new_disk;
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if (new_disk <= 0)
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new_disk = conf->raid_disks;
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new_disk--;
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if (new_disk == disk) {
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new_disk = -1;
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goto rb_out;
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new_disk = wonly_disk;
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break;
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}
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}
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if (new_disk < 0)
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goto rb_out;
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disk = new_disk;
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/* now disk == new_disk == starting point for search */
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@ -419,37 +435,41 @@ static int read_balance(conf_t *conf, r1bio_t *r1_bio)
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disk = conf->raid_disks;
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disk--;
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if ((rdev=conf->mirrors[disk].rdev) == NULL ||
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!rdev->in_sync)
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rdev = conf->mirrors[disk].rdev;
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if (!rdev ||
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!rdev->in_sync ||
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test_bit(WriteMostly, &rdev->flags))
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continue;
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if (!atomic_read(&rdev->nr_pending)) {
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new_disk = disk;
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new_rdev = rdev;
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break;
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}
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new_distance = abs(this_sector - conf->mirrors[disk].head_position);
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if (new_distance < current_distance) {
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current_distance = new_distance;
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new_disk = disk;
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new_rdev = rdev;
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}
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} while (disk != conf->last_used);
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rb_out:
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rb_out:
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if (new_disk >= 0) {
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conf->next_seq_sect = this_sector + sectors;
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conf->last_used = new_disk;
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atomic_inc(&new_rdev->nr_pending);
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if (!new_rdev->in_sync) {
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rdev = conf->mirrors[new_disk].rdev;
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if (!rdev)
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goto retry;
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atomic_inc(&rdev->nr_pending);
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if (!rdev->in_sync) {
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/* cannot risk returning a device that failed
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* before we inc'ed nr_pending
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*/
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atomic_dec(&new_rdev->nr_pending);
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atomic_dec(&rdev->nr_pending);
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goto retry;
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}
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conf->next_seq_sect = this_sector + sectors;
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conf->last_used = new_disk;
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}
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rcu_read_unlock();
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@ -1109,6 +1129,7 @@ static sector_t sync_request(mddev_t *mddev, sector_t sector_nr, int *skipped, i
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sector_t max_sector, nr_sectors;
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int disk;
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int i;
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int wonly;
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int write_targets = 0;
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int sync_blocks;
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int still_degraded = 0;
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@ -1164,14 +1185,21 @@ static sector_t sync_request(mddev_t *mddev, sector_t sector_nr, int *skipped, i
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*/
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disk = conf->last_used;
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/* make sure disk is operational */
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wonly = disk;
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while (conf->mirrors[disk].rdev == NULL ||
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!conf->mirrors[disk].rdev->in_sync) {
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!conf->mirrors[disk].rdev->in_sync ||
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test_bit(WriteMostly, &conf->mirrors[disk].rdev->flags)
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) {
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if (conf->mirrors[disk].rdev &&
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conf->mirrors[disk].rdev->in_sync)
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wonly = disk;
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if (disk <= 0)
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disk = conf->raid_disks;
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disk--;
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if (disk == conf->last_used)
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if (disk == conf->last_used) {
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disk = wonly;
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break;
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}
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}
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conf->last_used = disk;
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atomic_inc(&conf->mirrors[disk].rdev->nr_pending);
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@ -181,6 +181,9 @@ struct mdk_rdev_s
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int faulty; /* if faulty do not issue IO requests */
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int in_sync; /* device is a full member of the array */
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unsigned long flags; /* Should include faulty and in_sync here. */
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#define WriteMostly 4 /* Avoid reading if at all possible */
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int desc_nr; /* descriptor index in the superblock */
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int raid_disk; /* role of device in array */
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int saved_raid_disk; /* role that device used to have in the
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@ -79,6 +79,11 @@
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#define MD_DISK_SYNC 2 /* disk is in sync with the raid set */
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#define MD_DISK_REMOVED 3 /* disk is in sync with the raid set */
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#define MD_DISK_WRITEMOSTLY 9 /* disk is "write-mostly" is RAID1 config.
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* read requests will only be sent here in
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* dire need
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*/
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typedef struct mdp_device_descriptor_s {
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__u32 number; /* 0 Device number in the entire set */
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__u32 major; /* 1 Device major number */
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@ -193,7 +198,7 @@ struct mdp_superblock_1 {
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__u64 ctime; /* lo 40 bits are seconds, top 24 are microseconds or 0*/
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__u32 level; /* -4 (multipath), -1 (linear), 0,1,4,5 */
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__u32 layout; /* only for raid5 currently */
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__u32 layout; /* only for raid5 and raid10 currently */
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__u64 size; /* used size of component devices, in 512byte sectors */
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__u32 chunksize; /* in 512byte sectors */
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@ -212,7 +217,9 @@ struct mdp_superblock_1 {
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__u32 dev_number; /* permanent identifier of this device - not role in raid */
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__u32 cnt_corrected_read; /* number of read errors that were corrected by re-writing */
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__u8 device_uuid[16]; /* user-space setable, ignored by kernel */
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__u8 pad2[64-56]; /* set to 0 when writing */
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__u8 devflags; /* per-device flags. Only one defined...*/
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#define WriteMostly1 1 /* mask for writemostly flag in above */
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__u8 pad2[64-57]; /* set to 0 when writing */
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/* array state information - 64 bytes */
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__u64 utime; /* 40 bits second, 24 btes microseconds */
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