md: improve handling of bio with REQ_PREFLUSH in md_flush_request()

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>

diff --git a/drivers/md/md-linear.c b/drivers/md/md-linear.c
index c766c55..26c75c0 100644 (file)
--- 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 6780938..152f9e6 100644 (file)
--- 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 1be7abe..b8dd56b 100644 (file)
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -550,7 +550,13 @@ 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);
@@ -575,9 +581,10 @@ 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);
 

diff --git a/drivers/md/md.h b/drivers/md/md.h
index c5e3ff3..5f86f8a 100644 (file)
--- a/drivers/md/md.h
+++ b/drivers/md/md.h
@@ -550,7 +550,7 @@ 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()
@@ -703,7 +703,7 @@ 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 3956ea5..f2b83bd 100644 (file)
--- a/drivers/md/raid0.c
+++ b/drivers/md/raid0.c
@@ -575,10 +575,9 @@ 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 0466ee2..bb29aee 100644 (file)
--- a/drivers/md/raid1.c
+++ b/drivers/md/raid1.c
@@ -1567,10 +1567,9 @@ 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 299c7b1..2eca0a8 100644 (file)
--- a/drivers/md/raid10.c
+++ b/drivers/md/raid10.c
@@ -1525,10 +1525,9 @@ 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 223e97a..12a8ce8 100644 (file)
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -5592,8 +5592,8 @@ 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 */
                /*