dm thin: requeue bios to DM core if no_free_space and in read-only mode

Now that we switch the pool to read-only mode when the data device runs
out of space it causes active writers to get IO errors once we resume
after resizing the data device.

If no_free_space is set, save bios to the 'retry_on_resume_list' and
requeue them on resume (once the data or metadata device may have been
resized).

With this patch the resize_io test passes again (on slower storage):
 dmtest run --suite thin-provisioning -n /resize_io/

Later patches fix some subtle races associated with the pool mode
transitions done as part of the pool's -ENOSPC handling.  These races
are exposed on fast storage (e.g. PCIe SSD).

Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Acked-by: Joe Thornber <ejt@redhat.com>

1 files changed, 20 insertions, 6 deletions

diff --git a/drivers/md/dm-thin.c b/drivers/md/dm-thin.c
index 96ce36a1a764..53252d2af249 100644
--- a/drivers/md/dm-thin.c
+++ b/drivers/md/dm-thin.c
@@ -164,7 +164,7 @@ struct pool {
 
         struct pool_features pf;
         bool low_water_triggered:1;     /* A dm event has been sent */
-        bool no_free_space:1;           /* A -ENOSPC warning has been issued */
+        bool no_free_space:1;           /* bios will be requeued if set */
 
         struct dm_bio_prison *prison;
         struct dm_kcopyd_client *copier;
@@ -982,6 +982,20 @@ static void retry_on_resume(struct bio *bio)
         spin_unlock_irqrestore(&pool->lock, flags);
 }
 
+static void handle_unserviceable_bio(struct pool *pool, struct bio *bio)
+{
+        /*
+         * When pool is read-only, no cell locking is needed because
+         * nothing is changing.
+         */
+        WARN_ON_ONCE(get_pool_mode(pool) != PM_READ_ONLY);
+
+        if (pool->no_free_space)
+                retry_on_resume(bio);
+        else
+                bio_io_error(bio);
+}
+
 static void retry_bios_on_resume(struct pool *pool, struct dm_bio_prison_cell *cell)
 {
         struct bio *bio;
@@ -991,7 +1005,7 @@ static void retry_bios_on_resume(struct pool *pool, struct dm_bio_prison_cell *c
         cell_release(pool, cell, &bios);
 
         while ((bio = bio_list_pop(&bios)))
-                retry_on_resume(bio);
+                handle_unserviceable_bio(pool, bio);
 }
 
 static void process_discard(struct thin_c *tc, struct bio *bio)
@@ -1245,7 +1259,7 @@ static void process_bio_read_only(struct thin_c *tc, struct bio *bio)
         switch (r) {
         case 0:
                 if (lookup_result.shared && (rw == WRITE) && bio->bi_size)
-                        bio_io_error(bio);
+                        handle_unserviceable_bio(tc->pool, bio);
                 else {
                         inc_all_io_entry(tc->pool, bio);
                         remap_and_issue(tc, bio, lookup_result.block);
@@ -1254,7 +1268,7 @@ static void process_bio_read_only(struct thin_c *tc, struct bio *bio)
 
         case -ENODATA:
                 if (rw != READ) {
-                        bio_io_error(bio);
+                        handle_unserviceable_bio(tc->pool, bio);
                         break;
                 }
 
@@ -1565,9 +1579,9 @@ static int thin_bio_map(struct dm_target *ti, struct bio *bio)
                 if (get_pool_mode(tc->pool) == PM_READ_ONLY) {
                         /*
                          * This block isn't provisioned, and we have no way
-                         * of doing so.  Just error it.
+                         * of doing so.
                          */
-                        bio_io_error(bio);
+                        handle_unserviceable_bio(tc->pool, bio);
                         return DM_MAPIO_SUBMITTED;
                 }
                 /* fall through */