1 files changed, 102 insertions, 45 deletions

diff --git a/drivers/md/dm-thin.c b/drivers/md/dm-thin.c
index a04eba905922..38a063f7afa4 100644
--- a/drivers/md/dm-thin.c
+++ b/drivers/md/dm-thin.c
@@ -130,10 +130,11 @@ static void build_virtual_key(struct dm_thin_device *td, dm_block_t b,
 struct dm_thin_new_mapping;
 
 /*
- * The pool runs in 3 modes.  Ordered in degraded order for comparisons.
+ * The pool runs in 4 modes.  Ordered in degraded order for comparisons.
  */
 enum pool_mode {
         PM_WRITE,               /* metadata may be changed */
+        PM_OUT_OF_DATA_SPACE,   /* metadata may be changed, though data may not be allocated */
         PM_READ_ONLY,           /* metadata may not be changed */
         PM_FAIL,                /* all I/O fails */
 };
@@ -198,7 +199,6 @@ struct pool {
 };
 
 static enum pool_mode get_pool_mode(struct pool *pool);
-static void out_of_data_space(struct pool *pool);
 static void metadata_operation_failed(struct pool *pool, const char *op, int r);
 
 /*
@@ -399,6 +399,23 @@ static void requeue_io(struct thin_c *tc)
         spin_unlock_irqrestore(&pool->lock, flags);
 }
 
+static void error_retry_list(struct pool *pool)
+{
+        struct bio *bio;
+        unsigned long flags;
+        struct bio_list bios;
+
+        bio_list_init(&bios);
+
+        spin_lock_irqsave(&pool->lock, flags);
+        bio_list_merge(&bios, &pool->retry_on_resume_list);
+        bio_list_init(&pool->retry_on_resume_list);
+        spin_unlock_irqrestore(&pool->lock, flags);
+
+        while ((bio = bio_list_pop(&bios)))
+                bio_io_error(bio);
+}
+
 /*
  * This section of code contains the logic for processing a thin device's IO.
  * Much of the code depends on pool object resources (lists, workqueues, etc)
@@ -925,13 +942,15 @@ static void check_low_water_mark(struct pool *pool, dm_block_t free_blocks)
         }
 }
 
+static void set_pool_mode(struct pool *pool, enum pool_mode new_mode);
+
 static int alloc_data_block(struct thin_c *tc, dm_block_t *result)
 {
         int r;
         dm_block_t free_blocks;
         struct pool *pool = tc->pool;
 
-        if (get_pool_mode(pool) != PM_WRITE)
+        if (WARN_ON(get_pool_mode(pool) != PM_WRITE))
                 return -EINVAL;
 
         r = dm_pool_get_free_block_count(pool->pmd, &free_blocks);
@@ -958,7 +977,7 @@ static int alloc_data_block(struct thin_c *tc, dm_block_t *result)
                 }
 
                 if (!free_blocks) {
-                        out_of_data_space(pool);
+                        set_pool_mode(pool, PM_OUT_OF_DATA_SPACE);
                         return -ENOSPC;
                 }
         }
@@ -988,15 +1007,32 @@ 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)
+static bool should_error_unserviceable_bio(struct pool *pool)
 {
-        /*
-         * When pool is read-only, no cell locking is needed because
-         * nothing is changing.
-         */
-        WARN_ON_ONCE(get_pool_mode(pool) != PM_READ_ONLY);
+        enum pool_mode m = get_pool_mode(pool);
+
+        switch (m) {
+        case PM_WRITE:
+                /* Shouldn't get here */
+                DMERR_LIMIT("bio unserviceable, yet pool is in PM_WRITE mode");
+                return true;
+
+        case PM_OUT_OF_DATA_SPACE:
+                return pool->pf.error_if_no_space;
+
+        case PM_READ_ONLY:
+        case PM_FAIL:
+                return true;
+        default:
+                /* Shouldn't get here */
+                DMERR_LIMIT("bio unserviceable, yet pool has an unknown mode");
+                return true;
+        }
+}
 
-        if (pool->pf.error_if_no_space)
+static void handle_unserviceable_bio(struct pool *pool, struct bio *bio)
+{
+        if (should_error_unserviceable_bio(pool))
                 bio_io_error(bio);
         else
                 retry_on_resume(bio);
@@ -1007,11 +1043,20 @@ static void retry_bios_on_resume(struct pool *pool, struct dm_bio_prison_cell *c
         struct bio *bio;
         struct bio_list bios;
 
+        if (should_error_unserviceable_bio(pool)) {
+                cell_error(pool, cell);
+                return;
+        }
+
         bio_list_init(&bios);
         cell_release(pool, cell, &bios);
 
-        while ((bio = bio_list_pop(&bios)))
-                handle_unserviceable_bio(pool, bio);
+        if (should_error_unserviceable_bio(pool))
+                while ((bio = bio_list_pop(&bios)))
+                        bio_io_error(bio);
+        else
+                while ((bio = bio_list_pop(&bios)))
+                        retry_on_resume(bio);
 }
 
 static void process_discard(struct thin_c *tc, struct bio *bio)
@@ -1296,6 +1341,11 @@ static void process_bio_read_only(struct thin_c *tc, struct bio *bio)
         }
 }
 
+static void process_bio_success(struct thin_c *tc, struct bio *bio)
+{
+        bio_endio(bio, 0);
+}
+
 static void process_bio_fail(struct thin_c *tc, struct bio *bio)
 {
         bio_io_error(bio);
@@ -1399,9 +1449,15 @@ static enum pool_mode get_pool_mode(struct pool *pool)
         return pool->pf.mode;
 }
 
+static void notify_of_pool_mode_change(struct pool *pool, const char *new_mode)
+{
+        dm_table_event(pool->ti->table);
+        DMINFO("%s: switching pool to %s mode",
+               dm_device_name(pool->pool_md), new_mode);
+}
+
 static void set_pool_mode(struct pool *pool, enum pool_mode new_mode)
 {
-        int r;
         struct pool_c *pt = pool->ti->private;
         bool needs_check = dm_pool_metadata_needs_check(pool->pmd);
         enum pool_mode old_mode = get_pool_mode(pool);
@@ -1429,38 +1485,48 @@ static void set_pool_mode(struct pool *pool, enum pool_mode new_mode)
         switch (new_mode) {
         case PM_FAIL:
                 if (old_mode != new_mode)
-                        DMERR("%s: switching pool to failure mode",
-                              dm_device_name(pool->pool_md));
+                        notify_of_pool_mode_change(pool, "failure");
                 dm_pool_metadata_read_only(pool->pmd);
                 pool->process_bio = process_bio_fail;
                 pool->process_discard = process_bio_fail;
                 pool->process_prepared_mapping = process_prepared_mapping_fail;
                 pool->process_prepared_discard = process_prepared_discard_fail;
+
+                error_retry_list(pool);
                 break;
 
         case PM_READ_ONLY:
                 if (old_mode != new_mode)
-                        DMERR("%s: switching pool to read-only mode",
-                              dm_device_name(pool->pool_md));
-                r = dm_pool_abort_metadata(pool->pmd);
-                if (r) {
-                        DMERR("%s: aborting transaction failed",
-                              dm_device_name(pool->pool_md));
-                        new_mode = PM_FAIL;
-                        set_pool_mode(pool, new_mode);
-                } else {
-                        dm_pool_metadata_read_only(pool->pmd);
-                        pool->process_bio = process_bio_read_only;
-                        pool->process_discard = process_discard;
-                        pool->process_prepared_mapping = process_prepared_mapping_fail;
-                        pool->process_prepared_discard = process_prepared_discard_passdown;
-                }
+                        notify_of_pool_mode_change(pool, "read-only");
+                dm_pool_metadata_read_only(pool->pmd);
+                pool->process_bio = process_bio_read_only;
+                pool->process_discard = process_bio_success;
+                pool->process_prepared_mapping = process_prepared_mapping_fail;
+                pool->process_prepared_discard = process_prepared_discard_passdown;
+
+                error_retry_list(pool);
+                break;
+
+        case PM_OUT_OF_DATA_SPACE:
+                /*
+                 * Ideally we'd never hit this state; the low water mark
+                 * would trigger userland to extend the pool before we
+                 * completely run out of data space.  However, many small
+                 * IOs to unprovisioned space can consume data space at an
+                 * alarming rate.  Adjust your low water mark if you're
+                 * frequently seeing this mode.
+                 */
+                if (old_mode != new_mode)
+                        notify_of_pool_mode_change(pool, "out-of-data-space");
+                pool->process_bio = process_bio_read_only;
+                pool->process_discard = process_discard;
+                pool->process_prepared_mapping = process_prepared_mapping;
+                pool->process_prepared_discard = process_prepared_discard_passdown;
                 break;
 
         case PM_WRITE:
                 if (old_mode != new_mode)
-                        DMINFO("%s: switching pool to write mode",
-                               dm_device_name(pool->pool_md));
+                        notify_of_pool_mode_change(pool, "write");
                 dm_pool_metadata_read_write(pool->pmd);
                 pool->process_bio = process_bio;
                 pool->process_discard = process_discard;
@@ -1477,17 +1543,6 @@ static void set_pool_mode(struct pool *pool, enum pool_mode new_mode)
         pt->adjusted_pf.mode = new_mode;
 }
 
-/*
- * Rather than calling set_pool_mode directly, use these which describe the
- * reason for mode degradation.
- */
-static void out_of_data_space(struct pool *pool)
-{
-        DMERR_LIMIT("%s: no free data space available.",
-                    dm_device_name(pool->pool_md));
-        set_pool_mode(pool, PM_READ_ONLY);
-}
-
 static void abort_transaction(struct pool *pool)
 {
         const char *dev_name = dm_device_name(pool->pool_md);
@@ -2719,7 +2774,9 @@ static void pool_status(struct dm_target *ti, status_type_t type,
                 else
                         DMEMIT("- ");
 
-                if (pool->pf.mode == PM_READ_ONLY)
+                if (pool->pf.mode == PM_OUT_OF_DATA_SPACE)
+                        DMEMIT("out_of_data_space ");
+                else if (pool->pf.mode == PM_READ_ONLY)
                         DMEMIT("ro ");
                 else
                         DMEMIT("rw ");