handle_read_error() duplicates a lot of the work that raid1_read_request()
does, so it makes sense to just use that function.
This doesn't quite work as handle_read_error() relies on the same r1bio
being re-used so that, in the case of a read-only array, setting
IO_BLOCKED in r1bio->bios[] ensures read_balance() won't re-use
that device.
So we need to allow a r1bio to be passed to raid1_read_request(), and to
have that function mostly initialise the r1bio, but leave the bios[]
array untouched.
Two parts of handle_read_error() that need to be preserved are the warning
message it prints, so they are conditionally added to raid1_read_request().
Note that this highlights a minor bug on alloc_r1bio(). It doesn't
initalise the bios[] array, so it is possible that old content is there,
which might cause read_balance() to ignore some devices with no good reason.
With this change, we no longer need inc_pending(), or the sectors_handled
arg to alloc_r1bio().
As handle_read_error() is called from raid1d() and allocates memory,
there is tiny chance of a deadlock. All element of various pools
could be queued waiting for raid1 to handle them, and there may be no
extra memory free.
Achieving guaranteed forward progress would probably require a second
thread and another mempool. Instead of that complexity, add
__GFP_HIGH to any allocations when read1_read_request() is called
from raid1d.
Signed-off-by: NeilBrown <neilb@xxxxxxxx>
---
drivers/md/raid1.c | 138 ++++++++++++++++++++++------------------------------
1 file changed, 58 insertions(+), 80 deletions(-)
diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
index 06a13010f1b7..d15268fff052 100644
--- a/drivers/md/raid1.c
+++ b/drivers/md/raid1.c
@@ -988,16 +988,6 @@ static void wait_read_barrier(struct r1conf *conf, sector_t sector_nr)
spin_unlock_irq(&conf->resync_lock);
}
-static void inc_pending(struct r1conf *conf, sector_t bi_sector)
-{
- /* The current request requires multiple r1_bio, so
- * we need to increment the pending count, and the corresponding
- * window count.
- */
- int idx = sector_to_idx(bi_sector);
- atomic_inc(&conf->nr_pending[idx]);
-}
-
static void wait_barrier(struct r1conf *conf, sector_t sector_nr)
{
int idx = sector_to_idx(sector_nr);
@@ -1184,35 +1174,58 @@ static void raid1_unplug(struct blk_plug_cb *cb, bool from_schedule)
kfree(plug);
}
+static void init_r1bio(struct r1bio *r1_bio, struct mddev *mddev, struct bio *bio)
+{
+ r1_bio->master_bio = bio;
+ r1_bio->sectors = bio_sectors(bio);
+ r1_bio->state = 0;
+ r1_bio->mddev = mddev;
+ r1_bio->sector = bio->bi_iter.bi_sector;
+}
+
static inline struct r1bio *
-alloc_r1bio(struct mddev *mddev, struct bio *bio, sector_t sectors_handled)
+alloc_r1bio(struct mddev *mddev, struct bio *bio)
{
struct r1conf *conf = mddev->private;
struct r1bio *r1_bio;
r1_bio = mempool_alloc(conf->r1bio_pool, GFP_NOIO);
-
- r1_bio->master_bio = bio;
- r1_bio->sectors = bio_sectors(bio) - sectors_handled;
- r1_bio->state = 0;
- r1_bio->mddev = mddev;
- r1_bio->sector = bio->bi_iter.bi_sector + sectors_handled;
-
+ /* Ensure no bio records IO_BLOCKED */
+ memset(r1_bio->bios, 0, conf->raid_disks * sizeof(r1_bio->bios[0]));
+ init_r1bio(r1_bio, mddev, bio);
return r1_bio;
}
static void raid1_read_request(struct mddev *mddev, struct bio *bio,
- int max_read_sectors)
+ int max_read_sectors, struct r1bio *r1_bio)
{
struct r1conf *conf = mddev->private;
struct raid1_info *mirror;
- struct r1bio *r1_bio;
struct bio *read_bio;
struct bitmap *bitmap = mddev->bitmap;
const int op = bio_op(bio);
const unsigned long do_sync = (bio->bi_opf & REQ_SYNC);
int max_sectors;
int rdisk;
+ bool print_msg = !!r1_bio;
+ char b[BDEVNAME_SIZE];
+ /* If r1_bio is set, we are blocking the raid1d thread
+ * so there is a tiny risk of deadlock. So ask for
+ * emergency memory if needed.
+ */
+ gfp_t gfp = r1_bio ? (GFP_NOIO | __GFP_HIGH) : GFP_NOIO;
+
+ if (print_msg) {
+ /* Need to get the block device name carefully */
+ struct md_rdev *rdev;
+ rcu_read_lock();
+ rdev = rcu_dereference(conf->mirrors[r1_bio->read_disk].rdev);
+ if (rdev)
+ bdevname(rdev->bdev, b);
+ else
+ strcpy(b, "???");
+ rcu_read_unlock();
+ }
/*
* Still need barrier for READ in case that whole
@@ -1220,7 +1233,10 @@ static void raid1_read_request(struct mddev *mddev, struct bio *bio,
*/
wait_read_barrier(conf, bio->bi_iter.bi_sector);
- r1_bio = alloc_r1bio(mddev, bio, 0);
+ if (!r1_bio)
+ r1_bio = alloc_r1bio(mddev, bio);
+ else
+ init_r1bio(r1_bio, mddev, bio);
r1_bio->sectors = max_read_sectors;
/*
@@ -1231,11 +1247,23 @@ static void raid1_read_request(struct mddev *mddev, struct bio *bio,
if (rdisk < 0) {
/* couldn't find anywhere to read from */
+ if (print_msg) {
+ pr_crit_ratelimited("md/raid1:%s: %s: unrecoverable I/O read error for block %llu\n",
+ mdname(mddev),
+ b,
+ (unsigned long long)r1_bio->sector);
+ }
raid_end_bio_io(r1_bio);
return;
}
mirror = conf->mirrors + rdisk;
+ if (print_msg)
+ pr_info_ratelimited("md/raid1:%s: redirecting sector %llu to other mirror: %s\n",
+ mdname(mddev),
+ (unsigned long long)r1_bio->sector,
+ bdevname(mirror->rdev->bdev, b));
+
if (test_bit(WriteMostly, &mirror->rdev->flags) &&
bitmap) {
/*
@@ -1249,7 +1277,7 @@ static void raid1_read_request(struct mddev *mddev, struct bio *bio,
if (max_sectors < bio_sectors(bio)) {
struct bio *split = bio_split(bio, max_sectors,
- GFP_NOIO, conf->bio_split);
+ gfp, conf->bio_split);
bio_chain(split, bio);
generic_make_request(bio);
bio = split;
@@ -1259,7 +1287,7 @@ static void raid1_read_request(struct mddev *mddev, struct bio *bio,
r1_bio->read_disk = rdisk;
- read_bio = bio_clone_fast(bio, GFP_NOIO, mddev->bio_set);
+ read_bio = bio_clone_fast(bio, gfp, mddev->bio_set);
r1_bio->bios[rdisk] = read_bio;
@@ -1332,7 +1360,7 @@ static void raid1_write_request(struct mddev *mddev, struct bio *bio,
}
wait_barrier(conf, bio->bi_iter.bi_sector);
- r1_bio = alloc_r1bio(mddev, bio, 0);
+ r1_bio = alloc_r1bio(mddev, bio);
r1_bio->sectors = max_write_sectors;
if (conf->pending_count >= max_queued_requests) {
@@ -1552,7 +1580,7 @@ static void raid1_make_request(struct mddev *mddev, struct bio *bio)
bio->bi_iter.bi_sector, bio_sectors(bio));
if (bio_data_dir(bio) == READ)
- raid1_read_request(mddev, bio, sectors);
+ raid1_read_request(mddev, bio, sectors, NULL);
else
raid1_write_request(mddev, bio, sectors);
}
@@ -2442,11 +2470,8 @@ static void handle_write_finished(struct r1conf *conf, struct r1bio *r1_bio)
static void handle_read_error(struct r1conf *conf, struct r1bio *r1_bio)
{
- int disk;
- int max_sectors;
struct mddev *mddev = conf->mddev;
struct bio *bio;
- char b[BDEVNAME_SIZE];
struct md_rdev *rdev;
dev_t bio_dev;
sector_t bio_sector;
@@ -2462,7 +2487,6 @@ static void handle_read_error(struct r1conf *conf, struct r1bio *r1_bio)
*/
bio = r1_bio->bios[r1_bio->read_disk];
- bdevname(bio->bi_bdev, b);
bio_dev = bio->bi_bdev->bd_dev;
bio_sector = conf->mirrors[r1_bio->read_disk].rdev->data_offset + r1_bio->sector;
bio_put(bio);
@@ -2480,58 +2504,12 @@ static void handle_read_error(struct r1conf *conf, struct r1bio *r1_bio)
}
rdev_dec_pending(rdev, conf->mddev);
+ allow_barrier(conf, r1_bio->sector);
+ bio = r1_bio->master_bio;
-read_more:
- disk = read_balance(conf, r1_bio, &max_sectors);
- if (disk == -1) {
- pr_crit_ratelimited("md/raid1:%s: %s: unrecoverable I/O read error for block %llu\n",
- mdname(mddev), b, (unsigned long long)r1_bio->sector);
- raid_end_bio_io(r1_bio);
- } else {
- const unsigned long do_sync
- = r1_bio->master_bio->bi_opf & REQ_SYNC;
- r1_bio->read_disk = disk;
- bio = bio_clone_fast(r1_bio->master_bio, GFP_NOIO,
- mddev->bio_set);
- bio_trim(bio, r1_bio->sector - bio->bi_iter.bi_sector,
- max_sectors);
- r1_bio->bios[r1_bio->read_disk] = bio;
- rdev = conf->mirrors[disk].rdev;
- pr_info_ratelimited("md/raid1:%s: redirecting sector %llu to other mirror: %s\n",
- mdname(mddev),
- (unsigned long long)r1_bio->sector,
- bdevname(rdev->bdev, b));
- bio->bi_iter.bi_sector = r1_bio->sector + rdev->data_offset;
- bio->bi_bdev = rdev->bdev;
- bio->bi_end_io = raid1_end_read_request;
- bio_set_op_attrs(bio, REQ_OP_READ, do_sync);
- if (test_bit(FailFast, &rdev->flags) &&
- test_bit(R1BIO_FailFast, &r1_bio->state))
- bio->bi_opf |= MD_FAILFAST;
- bio->bi_private = r1_bio;
- if (max_sectors < r1_bio->sectors) {
- /* Drat - have to split this up more */
- struct bio *mbio = r1_bio->master_bio;
- int sectors_handled = (r1_bio->sector + max_sectors
- - mbio->bi_iter.bi_sector);
- r1_bio->sectors = max_sectors;
- bio_inc_remaining(mbio);
- trace_block_bio_remap(bdev_get_queue(bio->bi_bdev),
- bio, bio_dev, bio_sector);
- generic_make_request(bio);
- bio = NULL;
-
- r1_bio = alloc_r1bio(mddev, mbio, sectors_handled);
- set_bit(R1BIO_ReadError, &r1_bio->state);
- inc_pending(conf, r1_bio->sector);
-
- goto read_more;
- } else {
- trace_block_bio_remap(bdev_get_queue(bio->bi_bdev),
- bio, bio_dev, bio_sector);
- generic_make_request(bio);
- }
- }
+ /* Reuse the old r1_bio so that the IO_BLOCKED settings are preserved */
+ r1_bio->state = 0;
+ raid1_read_request(mddev, bio, r1_bio->sectors, r1_bio);
}
static void raid1d(struct md_thread *thread)
--
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