1 files changed, 174 insertions, 121 deletions

diff --git a/drivers/md/dm-snap.c b/drivers/md/dm-snap.c
index 475514bda9d0..14bd1a1815b1 100644
--- a/drivers/md/dm-snap.c
+++ b/drivers/md/dm-snap.c
@@ -392,6 +392,8 @@ static void read_snapshot_metadata(struct dm_snapshot *s)
                 down_write(&s->lock);
                 s->valid = 0;
                 up_write(&s->lock);
+
+                dm_table_event(s->table);
         }
 }
 
@@ -601,6 +603,11 @@ static void error_bios(struct bio *bio)
         }
 }
 
+static inline void error_snapshot_bios(struct pending_exception *pe)
+{
+        error_bios(bio_list_get(&pe->snapshot_bios));
+}
+
 static struct bio *__flush_bios(struct pending_exception *pe)
 {
         /*
@@ -616,6 +623,28 @@ static struct bio *__flush_bios(struct pending_exception *pe)
         return NULL;
 }
 
+static void __invalidate_snapshot(struct dm_snapshot *s,
+                                struct pending_exception *pe, int err)
+{
+        if (!s->valid)
+                return;
+
+        if (err == -EIO)
+                DMERR("Invalidating snapshot: Error reading/writing.");
+        else if (err == -ENOMEM)
+                DMERR("Invalidating snapshot: Unable to allocate exception.");
+
+        if (pe)
+                remove_exception(&pe->e);
+
+        if (s->store.drop_snapshot)
+                s->store.drop_snapshot(&s->store);
+
+        s->valid = 0;
+
+        dm_table_event(s->table);
+}
+
 static void pending_complete(struct pending_exception *pe, int success)
 {
         struct exception *e;
@@ -623,50 +652,53 @@ static void pending_complete(struct pending_exception *pe, int success)
         struct dm_snapshot *s = pe->snap;
         struct bio *flush = NULL;
 
-        if (success) {
-                e = alloc_exception();
-                if (!e) {
-                        DMWARN("Unable to allocate exception.");
-                        down_write(&s->lock);
-                        s->store.drop_snapshot(&s->store);
-                        s->valid = 0;
-                        flush = __flush_bios(pe);
-                        up_write(&s->lock);
-
-                        error_bios(bio_list_get(&pe->snapshot_bios));
-                        goto out;
-                }
-                *e = pe->e;
-
-                /*
-                 * Add a proper exception, and remove the
-                 * in-flight exception from the list.
-                 */
+        if (!success) {
+                /* Read/write error - snapshot is unusable */
                 down_write(&s->lock);
-                insert_exception(&s->complete, e);
-                remove_exception(&pe->e);
+                __invalidate_snapshot(s, pe, -EIO);
                 flush = __flush_bios(pe);
-
-                /* Submit any pending write bios */
                 up_write(&s->lock);
 
-                flush_bios(bio_list_get(&pe->snapshot_bios));
-        } else {
-                /* Read/write error - snapshot is unusable */
+                error_snapshot_bios(pe);
+                goto out;
+        }
+
+        e = alloc_exception();
+        if (!e) {
                 down_write(&s->lock);
-                if (s->valid)
-                        DMERR("Error reading/writing snapshot");
-                s->store.drop_snapshot(&s->store);
-                s->valid = 0;
-                remove_exception(&pe->e);
+                __invalidate_snapshot(s, pe, -ENOMEM);
                 flush = __flush_bios(pe);
                 up_write(&s->lock);
 
-                error_bios(bio_list_get(&pe->snapshot_bios));
+                error_snapshot_bios(pe);
+                goto out;
+        }
+        *e = pe->e;
 
-                dm_table_event(s->table);
+        /*
+         * Add a proper exception, and remove the
+         * in-flight exception from the list.
+         */
+        down_write(&s->lock);
+        if (!s->valid) {
+                flush = __flush_bios(pe);
+                up_write(&s->lock);
+
+                free_exception(e);
+
+                error_snapshot_bios(pe);
+                goto out;
         }
 
+        insert_exception(&s->complete, e);
+        remove_exception(&pe->e);
+        flush = __flush_bios(pe);
+
+        up_write(&s->lock);
+
+        /* Submit any pending write bios */
+        flush_bios(bio_list_get(&pe->snapshot_bios));
+
  out:
         primary_pe = pe->primary_pe;
 
@@ -758,39 +790,45 @@ __find_pending_exception(struct dm_snapshot *s, struct bio *bio)
         if (e) {
                 /* cast the exception to a pending exception */
                 pe = container_of(e, struct pending_exception, e);
+                goto out;
+        }
 
-        } else {
-                /*
-                 * Create a new pending exception, we don't want
-                 * to hold the lock while we do this.
-                 */
-                up_write(&s->lock);
-                pe = alloc_pending_exception();
-                down_write(&s->lock);
+        /*
+         * Create a new pending exception, we don't want
+         * to hold the lock while we do this.
+         */
+        up_write(&s->lock);
+        pe = alloc_pending_exception();
+        down_write(&s->lock);
 
-                e = lookup_exception(&s->pending, chunk);
-                if (e) {
-                        free_pending_exception(pe);
-                        pe = container_of(e, struct pending_exception, e);
-                } else {
-                        pe->e.old_chunk = chunk;
-                        bio_list_init(&pe->origin_bios);
-                        bio_list_init(&pe->snapshot_bios);
-                        pe->primary_pe = NULL;
-                        atomic_set(&pe->sibling_count, 1);
-                        pe->snap = s;
-                        pe->started = 0;
-
-                        if (s->store.prepare_exception(&s->store, &pe->e)) {
-                                free_pending_exception(pe);
-                                s->valid = 0;
-                                return NULL;
-                        }
+        if (!s->valid) {
+                free_pending_exception(pe);
+                return NULL;
+        }
 
-                        insert_exception(&s->pending, &pe->e);
-                }
+        e = lookup_exception(&s->pending, chunk);
+        if (e) {
+                free_pending_exception(pe);
+                pe = container_of(e, struct pending_exception, e);
+                goto out;
         }
 
+        pe->e.old_chunk = chunk;
+        bio_list_init(&pe->origin_bios);
+        bio_list_init(&pe->snapshot_bios);
+        pe->primary_pe = NULL;
+        atomic_set(&pe->sibling_count, 1);
+        pe->snap = s;
+        pe->started = 0;
+
+        if (s->store.prepare_exception(&s->store, &pe->e)) {
+                free_pending_exception(pe);
+                return NULL;
+        }
+
+        insert_exception(&s->pending, &pe->e);
+
+ out:
         return pe;
 }
 
@@ -807,13 +845,15 @@ static int snapshot_map(struct dm_target *ti, struct bio *bio,
 {
         struct exception *e;
         struct dm_snapshot *s = (struct dm_snapshot *) ti->private;
+        int copy_needed = 0;
         int r = 1;
         chunk_t chunk;
-        struct pending_exception *pe;
+        struct pending_exception *pe = NULL;
 
         chunk = sector_to_chunk(s, bio->bi_sector);
 
         /* Full snapshots are not usable */
+        /* To get here the table must be live so s->active is always set. */
         if (!s->valid)
                 return -EIO;
 
@@ -831,36 +871,41 @@ static int snapshot_map(struct dm_target *ti, struct bio *bio,
                  * to copy an exception */
                 down_write(&s->lock);
 
+                if (!s->valid) {
+                        r = -EIO;
+                        goto out_unlock;
+                }
+
                 /* If the block is already remapped - use that, else remap it */
                 e = lookup_exception(&s->complete, chunk);
                 if (e) {
                         remap_exception(s, e, bio);
-                        up_write(&s->lock);
-
-                } else {
-                        pe = __find_pending_exception(s, bio);
-
-                        if (!pe) {
-                                if (s->store.drop_snapshot)
-                                        s->store.drop_snapshot(&s->store);
-                                s->valid = 0;
-                                r = -EIO;
-                                up_write(&s->lock);
-                        } else {
-                                remap_exception(s, &pe->e, bio);
-                                bio_list_add(&pe->snapshot_bios, bio);
-
-                                if (!pe->started) {
-                                        /* this is protected by snap->lock */
-                                        pe->started = 1;
-                                        up_write(&s->lock);
-                                        start_copy(pe);
-                                } else
-                                        up_write(&s->lock);
-                                r = 0;
-                        }
+                        goto out_unlock;
+                }
+
+                pe = __find_pending_exception(s, bio);
+                if (!pe) {
+                        __invalidate_snapshot(s, pe, -ENOMEM);
+                        r = -EIO;
+                        goto out_unlock;
                 }
 
+                remap_exception(s, &pe->e, bio);
+                bio_list_add(&pe->snapshot_bios, bio);
+
+                if (!pe->started) {
+                        /* this is protected by snap->lock */
+                        pe->started = 1;
+                        copy_needed = 1;
+                }
+
+                r = 0;
+
+ out_unlock:
+                up_write(&s->lock);
+
+                if (copy_needed)
+                        start_copy(pe);
         } else {
                 /*
                  * FIXME: this read path scares me because we
@@ -872,6 +917,11 @@ static int snapshot_map(struct dm_target *ti, struct bio *bio,
                 /* Do reads */
                 down_read(&s->lock);
 
+                if (!s->valid) {
+                        up_read(&s->lock);
+                        return -EIO;
+                }
+
                 /* See if it it has been remapped */
                 e = lookup_exception(&s->complete, chunk);
                 if (e)
@@ -948,15 +998,15 @@ static int __origin_write(struct list_head *snapshots, struct bio *bio)
         /* Do all the snapshots on this origin */
         list_for_each_entry (snap, snapshots, list) {
 
+                down_write(&snap->lock);
+
                 /* Only deal with valid and active snapshots */
                 if (!snap->valid || !snap->active)
-                        continue;
+                        goto next_snapshot;
 
                 /* Nothing to do if writing beyond end of snapshot */
                 if (bio->bi_sector >= dm_table_get_size(snap->table))
-                        continue;
-
-                down_write(&snap->lock);
+                        goto next_snapshot;
 
                 /*
                  * Remember, different snapshots can have
@@ -973,40 +1023,43 @@ static int __origin_write(struct list_head *snapshots, struct bio *bio)
                  * won't destroy the primary_pe while we're inside this loop.
                  */
                 e = lookup_exception(&snap->complete, chunk);
-                if (!e) {
-                        pe = __find_pending_exception(snap, bio);
-                        if (!pe) {
-                                snap->store.drop_snapshot(&snap->store);
-                                snap->valid = 0;
-
-                        } else {
-                                if (!primary_pe) {
-                                        /*
-                                         * Either every pe here has same
-                                         * primary_pe or none has one yet.
-                                         */
-                                        if (pe->primary_pe)
-                                                primary_pe = pe->primary_pe;
-                                        else {
-                                                primary_pe = pe;
-                                                first = 1;
-                                        }
-
-                                        bio_list_add(&primary_pe->origin_bios,
-                                                     bio);
-                                        r = 0;
-                                }
-                                if (!pe->primary_pe) {
-                                        atomic_inc(&primary_pe->sibling_count);
-                                        pe->primary_pe = primary_pe;
-                                }
-                                if (!pe->started) {
-                                        pe->started = 1;
-                                        list_add_tail(&pe->list, &pe_queue);
-                                }
+                if (e)
+                        goto next_snapshot;
+
+                pe = __find_pending_exception(snap, bio);
+                if (!pe) {
+                        __invalidate_snapshot(snap, pe, ENOMEM);
+                        goto next_snapshot;
+                }
+
+                if (!primary_pe) {
+                        /*
+                         * Either every pe here has same
+                         * primary_pe or none has one yet.
+                         */
+                        if (pe->primary_pe)
+                                primary_pe = pe->primary_pe;
+                        else {
+                                primary_pe = pe;
+                                first = 1;
                         }
+
+                        bio_list_add(&primary_pe->origin_bios, bio);
+
+                        r = 0;
+                }
+
+                if (!pe->primary_pe) {
+                        atomic_inc(&primary_pe->sibling_count);
+                        pe->primary_pe = primary_pe;
+                }
+
+                if (!pe->started) {
+                        pe->started = 1;
+                        list_add_tail(&pe->list, &pe_queue);
                 }
 
+ next_snapshot:
                 up_write(&snap->lock);
         }