From: Yu Kuai <yukuai3@xxxxxxxxxx>
behind write rely on bitmap, because the number of IO are recoreded in
bitmap->behind_writes, and callers rely on bitmap_wait_behind_writes()
to wait for IO to be done.
Hence if behind write start without bitmap, readers will not wait for
the IO to be done because bitmap_wait_behind_writes() do nothing,
and old data can be read.
Signed-off-by: Yu Kuai <yukuai3@xxxxxxxxxx>
---
drivers/md/md-bitmap.c | 6 ------
drivers/md/raid1.c | 45 ++++++++++++++++++++++++++----------------
2 files changed, 28 insertions(+), 23 deletions(-)
diff --git a/drivers/md/md-bitmap.c b/drivers/md/md-bitmap.c
index f87236225826..72cbbe0d3408 100644
--- a/drivers/md/md-bitmap.c
+++ b/drivers/md/md-bitmap.c
@@ -2031,9 +2031,6 @@ static void bitmap_start_behind_write(struct mddev *mddev)
struct bitmap *bitmap = mddev->bitmap;
int bw;
- if (!bitmap)
- return;
-
atomic_inc(&bitmap->behind_writes);
bw = atomic_read(&bitmap->behind_writes);
if (bw > bitmap->behind_writes_used)
@@ -2047,9 +2044,6 @@ static void bitmap_end_behind_write(struct mddev *mddev)
{
struct bitmap *bitmap = mddev->bitmap;
- if (!bitmap)
- return;
-
if (atomic_dec_and_test(&bitmap->behind_writes))
wake_up(&bitmap->behind_wait);
pr_debug("dec write-behind count %d/%lu\n",
diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
index a931e52bdfe3..bb1cadfcf54b 100644
--- a/drivers/md/raid1.c
+++ b/drivers/md/raid1.c
@@ -1369,7 +1369,8 @@ static void raid1_read_request(struct mddev *mddev, struct bio *bio,
(unsigned long long)r1_bio->sector,
mirror->rdev->bdev);
- if (test_bit(WriteMostly, &mirror->rdev->flags)) {
+ if (test_bit(WriteMostly, &mirror->rdev->flags) &&
+ md_bitmap_enabled(mddev)) {
/*
* Reading from a write-mostly device must take care not to
* over-take any writes that are 'behind'
@@ -1456,6 +1457,30 @@ static bool wait_blocked_rdev(struct mddev *mddev, struct bio *bio)
return true;
}
+static void raid1_start_write_behind(struct mddev *mddev, struct r1bio *r1_bio,
+ struct bio *bio)
+{
+ unsigned long max_write_behind = mddev->bitmap_info.max_write_behind;
+ struct md_bitmap_stats stats;
+ int err;
+
+ /* behind write rely on bitmap, see bitmap_operations */
+ if (!md_bitmap_enabled(mddev))
+ return;
+
+ err = mddev->bitmap_ops->get_stats(mddev->bitmap, &stats);
+ if (err)
+ return;
+
+ /* Don't do behind IO if reader is waiting, or there are too many. */
+ if (!stats.behind_wait && stats.behind_writes < max_write_behind)
+ alloc_behind_master_bio(r1_bio, bio);
+
+ if (test_bit(R1BIO_BehindIO, &r1_bio->state))
+ mddev->bitmap_ops->start_behind_write(mddev);
+
+}
+
static void raid1_write_request(struct mddev *mddev, struct bio *bio,
int max_write_sectors)
{
@@ -1629,22 +1654,8 @@ static void raid1_write_request(struct mddev *mddev, struct bio *bio,
continue;
if (first_clone) {
- unsigned long max_write_behind =
- mddev->bitmap_info.max_write_behind;
- struct md_bitmap_stats stats;
- int err;
-
- /* do behind I/O ?
- * Not if there are too many, or cannot
- * allocate memory, or a reader on WriteMostly
- * is waiting for behind writes to flush */
- err = mddev->bitmap_ops->get_stats(mddev->bitmap, &stats);
- if (!err && write_behind && !stats.behind_wait &&
- stats.behind_writes < max_write_behind)
- alloc_behind_master_bio(r1_bio, bio);
-
- if (test_bit(R1BIO_BehindIO, &r1_bio->state))
- mddev->bitmap_ops->start_behind_write(mddev);
+ if (write_behind)
+ raid1_start_write_behind(mddev, r1_bio, bio);
first_clone = 0;
}
--
2.39.2
