On 09/17/2019 01:15 AM, David Jeffery wrote:
Calling md_handle_request is certainly the simplest way to fix the issue,
but after more thought I don't think it's the best way. When the code gets
to md_flush_request, the code already has md_handle_request and the raid
driver's make_request function in the stack.
To fix the lost I/O, instead of recursing back into md_handle_request we
can pass back a bool to indicate if the original make_request call should
continue to handle the I/O and instead of assuming the flush logic will
push it to completion.
This patch converts md_flush_request to return a bool and no longer calls
the raid driver's make_request function. If the return is true, then the
md flush logic has or will complete the bio and the md make_request call
is done. If false, then the md make_request function needs to keep
processing like it is a normal I/O carrying bio. Let the original call to
md_handle_request handle any need to retry sending the bio to the raid
driver's make_request function should it be needed.
This also marks md_flush_request and the make_request function pointer as
__must_check to issue warnings should these critical return values be
ignored.
Signed-of-by: David Jeffery <djeffery@xxxxxxxxxx>
diff --git a/drivers/md/md-linear.c b/drivers/md/md-linear.c
index 7354466ddc90..afcf1d388300 100644
--- a/drivers/md/md-linear.c
+++ b/drivers/md/md-linear.c
@@ -244,10 +244,9 @@ static bool linear_make_request(struct mddev *mddev, struct bio *bio)
sector_t start_sector, end_sector, data_offset;
sector_t bio_sector = bio->bi_iter.bi_sector;
- if (unlikely(bio->bi_opf & REQ_PREFLUSH)) {
- md_flush_request(mddev, bio);
+ if (unlikely(bio->bi_opf & REQ_PREFLUSH)
+ && md_flush_request(mddev, bio))
return true;
- }
tmp_dev = which_dev(mddev, bio_sector);
start_sector = tmp_dev->end_sector - tmp_dev->rdev->sectors;
diff --git a/drivers/md/md-multipath.c b/drivers/md/md-multipath.c
index 6780938d2991..152f9e65a226 100644
--- a/drivers/md/md-multipath.c
+++ b/drivers/md/md-multipath.c
@@ -104,10 +104,9 @@ static bool multipath_make_request(struct mddev *mddev, struct bio * bio)
struct multipath_bh * mp_bh;
struct multipath_info *multipath;
- if (unlikely(bio->bi_opf & REQ_PREFLUSH)) {
- md_flush_request(mddev, bio);
+ if (unlikely(bio->bi_opf & REQ_PREFLUSH)
+ && md_flush_request(mddev, bio))
return true;
- }
mp_bh = mempool_alloc(&conf->pool, GFP_NOIO);
diff --git a/drivers/md/md.c b/drivers/md/md.c
index 24638ccedce4..d2c23f7b1008 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -545,7 +545,13 @@ static void md_submit_flush_data(struct work_struct *ws)
}
}
-void md_flush_request(struct mddev *mddev, struct bio *bio)
+/*
+ * Manages consolidation of flushes and submitting any flushes needed for
+ * a bio with REQ_PREFLUSH. Returns true if the bio is finished or is
+ * being finished in another context. Returns false if the flushing is
+ * complete but still needs the I/O portion of the bio to be processed.
+ */
+bool md_flush_request(struct mddev *mddev, struct bio *bio)
{
ktime_t start = ktime_get_boottime();
spin_lock_irq(&mddev->lock);
@@ -570,9 +576,10 @@ void md_flush_request(struct mddev *mddev, struct bio *bio)
bio_endio(bio);
else {
bio->bi_opf &= ~REQ_PREFLUSH;
- mddev->pers->make_request(mddev, bio);
+ return false;
}
}
+ return true;
}
EXPORT_SYMBOL(md_flush_request);
Hi David
md_flush_request returns false when one flush bio has data and
pers->make_request function go
on handling it. For example the raid device is raid1. md_flush_request
returns false, raid1_make_request
go on handling the bio. If raid1_make_request fails, the bio is still
lost. Now it looks like only md_handle_request
checks the return value of pers->make_request and go on handling the bio
if pers->make_request fails.
There should not be a deadlock if it calls md_handle_request directly.
Am I right? If there is a risk, we
can put those bios into a list and queue a work in workqueue to handle
them. Is it a better way?
Regards
Xiao
diff --git a/drivers/md/md.h b/drivers/md/md.h
index 10f98200e2f8..70d1dddf410b 100644
--- a/drivers/md/md.h
+++ b/drivers/md/md.h
@@ -543,7 +543,7 @@ struct md_personality
int level;
struct list_head list;
struct module *owner;
- bool (*make_request)(struct mddev *mddev, struct bio *bio);
+ bool __must_check (*make_request)(struct mddev *mddev, struct bio *bio);
/*
* start up works that do NOT require md_thread. tasks that
* requires md_thread should go into start()
@@ -696,7 +696,7 @@ extern void md_error(struct mddev *mddev, struct md_rdev *rdev);
extern void md_finish_reshape(struct mddev *mddev);
extern int mddev_congested(struct mddev *mddev, int bits);
-extern void md_flush_request(struct mddev *mddev, struct bio *bio);
+extern bool __must_check md_flush_request(struct mddev *mddev, struct bio *bio);
extern void md_super_write(struct mddev *mddev, struct md_rdev *rdev,
sector_t sector, int size, struct page *page);
extern int md_super_wait(struct mddev *mddev);
diff --git a/drivers/md/raid0.c b/drivers/md/raid0.c
index bf5cf184a260..2071437b80ca 100644
--- a/drivers/md/raid0.c
+++ b/drivers/md/raid0.c
@@ -554,10 +554,9 @@ static bool raid0_make_request(struct mddev *mddev, struct bio *bio)
unsigned chunk_sects;
unsigned sectors;
- if (unlikely(bio->bi_opf & REQ_PREFLUSH)) {
- md_flush_request(mddev, bio);
+ if (unlikely(bio->bi_opf & REQ_PREFLUSH)
+ && md_flush_request(mddev, bio))
return true;
- }
if (unlikely((bio_op(bio) == REQ_OP_DISCARD))) {
raid0_handle_discard(mddev, bio);
diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
index 34e26834ad28..576c02eae286 100644
--- a/drivers/md/raid1.c
+++ b/drivers/md/raid1.c
@@ -1562,10 +1562,9 @@ static bool raid1_make_request(struct mddev *mddev, struct bio *bio)
{
sector_t sectors;
- if (unlikely(bio->bi_opf & REQ_PREFLUSH)) {
- md_flush_request(mddev, bio);
+ if (unlikely(bio->bi_opf & REQ_PREFLUSH)
+ && md_flush_request(mddev, bio))
return true;
- }
/*
* There is a limit to the maximum size, but
diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
index 8a1354a08a1a..c5c134b3868b 100644
--- a/drivers/md/raid10.c
+++ b/drivers/md/raid10.c
@@ -1523,10 +1523,9 @@ static bool raid10_make_request(struct mddev *mddev, struct bio *bio)
int chunk_sects = chunk_mask + 1;
int sectors = bio_sectors(bio);
- if (unlikely(bio->bi_opf & REQ_PREFLUSH)) {
- md_flush_request(mddev, bio);
+ if (unlikely(bio->bi_opf & REQ_PREFLUSH)
+ && md_flush_request(mddev, bio))
return true;
- }
if (!md_write_start(mddev, bio))
return false;
diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 3de4e13bde98..ce935e95e32f 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -5584,8 +5584,8 @@ static bool raid5_make_request(struct mddev *mddev, struct bio * bi)
if (ret == 0)
return true;
if (ret == -ENODEV) {
- md_flush_request(mddev, bi);
- return true;
+ if (md_flush_request(mddev, bi))
+ return true;
}
/* ret == -EAGAIN, fallback */
/*
