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Subject[PATCH 4.19 058/140] md: improve handling of bio with REQ_PREFLUSH in md_flush_request()
Date
From: David Jeffery <djeffery@redhat.com>

commit 775d78319f1ceb32be8eb3b1202ccdc60e9cb7f1 upstream.

If pers->make_request fails in md_flush_request(), the bio is lost. To
fix this, 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.

Convert 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 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.

Also mark md_flush_request and the make_request function pointer as
__must_check to issue warnings should these critical return values be
ignored.

Fixes: 2bc13b83e629 ("md: batch flush requests.")
Cc: stable@vger.kernel.org # # v4.19+
Cc: NeilBrown <neilb@suse.com>
Signed-off-by: David Jeffery <djeffery@redhat.com>
Reviewed-by: Xiao Ni <xni@redhat.com>
Signed-off-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/md/md-linear.c | 5 ++---
drivers/md/md-multipath.c | 5 ++---
drivers/md/md.c | 11 +++++++++--
drivers/md/md.h | 4 ++--
drivers/md/raid0.c | 5 ++---
drivers/md/raid1.c | 5 ++---
drivers/md/raid10.c | 5 ++---
drivers/md/raid5.c | 4 ++--
8 files changed, 23 insertions(+), 21 deletions(-)

--- a/drivers/md/md-linear.c
+++ b/drivers/md/md-linear.c
@@ -252,10 +252,9 @@ static bool linear_make_request(struct m
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;
--- a/drivers/md/md-multipath.c
+++ b/drivers/md/md-multipath.c
@@ -112,10 +112,9 @@ static bool multipath_make_request(struc
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);

--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -487,7 +487,13 @@ static void md_submit_flush_data(struct
}
}

-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);
@@ -512,9 +518,10 @@ void md_flush_request(struct mddev *mdde
bio_endio(bio);
else {
bio->bi_opf &= ~REQ_PREFLUSH;
- mddev->pers->make_request(mddev, bio);
+ return false;
}
}
+ return true;
}
EXPORT_SYMBOL(md_flush_request);

--- a/drivers/md/md.h
+++ b/drivers/md/md.h
@@ -532,7 +532,7 @@ 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()
@@ -684,7 +684,7 @@ extern void md_error(struct mddev *mddev
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);
--- a/drivers/md/raid0.c
+++ b/drivers/md/raid0.c
@@ -580,10 +580,9 @@ static bool raid0_make_request(struct md
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);
--- a/drivers/md/raid1.c
+++ b/drivers/md/raid1.c
@@ -1537,10 +1537,9 @@ static bool raid1_make_request(struct md
{
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
--- a/drivers/md/raid10.c
+++ b/drivers/md/raid10.c
@@ -1562,10 +1562,9 @@ static bool raid10_make_request(struct m
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;
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -5590,8 +5590,8 @@ static bool raid5_make_request(struct md
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 */
/*

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