4 files changed, 265 insertions, 45 deletions

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index ed1e25d72483..1d3e9262a9da 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -1533,6 +1533,11 @@ out:
  * struct refsort is used to match byte number to slot in the btree block.
  * we sort based on the byte number and then use the slot to actually
  * find the item.
+ *
+ * struct refsort is smaller than strcut btrfs_item and smaller than
+ * struct btrfs_key_ptr.  Since we're currently limited to the page size
+ * for a btree block, there's no way for a kmalloc of refsorts for a
+ * single node to be bigger than a page.
  */
 struct refsort {
         u64 bytenr;
@@ -3457,36 +3462,73 @@ int btrfs_drop_leaf_ref(struct btrfs_trans_handle *trans,
 {
         u64 leaf_owner;
         u64 leaf_generation;
+        struct refsort *sorted;
         struct btrfs_key key;
         struct btrfs_file_extent_item *fi;
         int i;
         int nritems;
         int ret;
+        int refi = 0;
+        int slot;
 
         BUG_ON(!btrfs_is_leaf(leaf));
         nritems = btrfs_header_nritems(leaf);
         leaf_owner = btrfs_header_owner(leaf);
         leaf_generation = btrfs_header_generation(leaf);
 
+        sorted = kmalloc(sizeof(*sorted) * nritems, GFP_NOFS);
+        /* we do this loop twice.  The first time we build a list
+         * of the extents we have a reference on, then we sort the list
+         * by bytenr.  The second time around we actually do the
+         * extent freeing.
+         */
         for (i = 0; i < nritems; i++) {
                 u64 disk_bytenr;
                 cond_resched();
 
                 btrfs_item_key_to_cpu(leaf, &key, i);
+
+                /* only extents have references, skip everything else */
                 if (btrfs_key_type(&key) != BTRFS_EXTENT_DATA_KEY)
                         continue;
+
                 fi = btrfs_item_ptr(leaf, i, struct btrfs_file_extent_item);
+
+                /* inline extents live in the btree, they don't have refs */
                 if (btrfs_file_extent_type(leaf, fi) ==
                     BTRFS_FILE_EXTENT_INLINE)
                         continue;
-                /*
-                 * FIXME make sure to insert a trans record that
-                 * repeats the snapshot del on crash
-                 */
+
                 disk_bytenr = btrfs_file_extent_disk_bytenr(leaf, fi);
+
+                /* holes don't have refs */
                 if (disk_bytenr == 0)
                         continue;
 
+                sorted[refi].bytenr = disk_bytenr;
+                sorted[refi].slot = i;
+                refi++;
+        }
+
+        if (refi == 0)
+                goto out;
+
+        sort(sorted, refi, sizeof(struct refsort), refsort_cmp, NULL);
+
+        for (i = 0; i < refi; i++) {
+                u64 disk_bytenr;
+
+                disk_bytenr = sorted[i].bytenr;
+                slot = sorted[i].slot;
+
+                cond_resched();
+
+                btrfs_item_key_to_cpu(leaf, &key, slot);
+                if (btrfs_key_type(&key) != BTRFS_EXTENT_DATA_KEY)
+                        continue;
+
+                fi = btrfs_item_ptr(leaf, slot, struct btrfs_file_extent_item);
+
                 ret = __btrfs_free_extent(trans, root, disk_bytenr,
                                 btrfs_file_extent_disk_num_bytes(leaf, fi),
                                 leaf->start, leaf_owner, leaf_generation,
@@ -3497,6 +3539,8 @@ int btrfs_drop_leaf_ref(struct btrfs_trans_handle *trans,
                 wake_up(&root->fs_info->transaction_throttle);
                 cond_resched();
         }
+out:
+        kfree(sorted);
         return 0;
 }
 
@@ -3506,9 +3550,25 @@ static noinline int cache_drop_leaf_ref(struct btrfs_trans_handle *trans,
 {
         int i;
         int ret;
-        struct btrfs_extent_info *info = ref->extents;
+        struct btrfs_extent_info *info;
+        struct refsort *sorted;
+
+        if (ref->nritems == 0)
+                return 0;
 
+        sorted = kmalloc(sizeof(*sorted) * ref->nritems, GFP_NOFS);
+        for (i = 0; i < ref->nritems; i++) {
+                sorted[i].bytenr = ref->extents[i].bytenr;
+                sorted[i].slot = i;
+        }
+        sort(sorted, ref->nritems, sizeof(struct refsort), refsort_cmp, NULL);
+
+        /*
+         * the items in the ref were sorted when the ref was inserted
+         * into the ref cache, so this is already in order
+         */
         for (i = 0; i < ref->nritems; i++) {
+                info = ref->extents + sorted[i].slot;
                 ret = __btrfs_free_extent(trans, root, info->bytenr,
                                           info->num_bytes, ref->bytenr,
                                           ref->owner, ref->generation,
@@ -3566,6 +3626,152 @@ static int drop_snap_lookup_refcount(struct btrfs_root *root, u64 start,
 }
 
 /*
+ * this is used while deleting old snapshots, and it drops the refs
+ * on a whole subtree starting from a level 1 node.
+ *
+ * The idea is to sort all the leaf pointers, and then drop the
+ * ref on all the leaves in order.  Most of the time the leaves
+ * will have ref cache entries, so no leaf IOs will be required to
+ * find the extents they have references on.
+ *
+ * For each leaf, any references it has are also dropped in order
+ *
+ * This ends up dropping the references in something close to optimal
+ * order for reading and modifying the extent allocation tree.
+ */
+static noinline int drop_level_one_refs(struct btrfs_trans_handle *trans,
+                                        struct btrfs_root *root,
+                                        struct btrfs_path *path)
+{
+        u64 bytenr;
+        u64 root_owner;
+        u64 root_gen;
+        struct extent_buffer *eb = path->nodes[1];
+        struct extent_buffer *leaf;
+        struct btrfs_leaf_ref *ref;
+        struct refsort *sorted = NULL;
+        int nritems = btrfs_header_nritems(eb);
+        int ret;
+        int i;
+        int refi = 0;
+        int slot = path->slots[1];
+        u32 blocksize = btrfs_level_size(root, 0);
+        u32 refs;
+
+        if (nritems == 0)
+                goto out;
+
+        root_owner = btrfs_header_owner(eb);
+        root_gen = btrfs_header_generation(eb);
+        sorted = kmalloc(sizeof(*sorted) * nritems, GFP_NOFS);
+
+        /*
+         * step one, sort all the leaf pointers so we don't scribble
+         * randomly into the extent allocation tree
+         */
+        for (i = slot; i < nritems; i++) {
+                sorted[refi].bytenr = btrfs_node_blockptr(eb, i);
+                sorted[refi].slot = i;
+                refi++;
+        }
+
+        /*
+         * nritems won't be zero, but if we're picking up drop_snapshot
+         * after a crash, slot might be > 0, so double check things
+         * just in case.
+         */
+        if (refi == 0)
+                goto out;
+
+        sort(sorted, refi, sizeof(struct refsort), refsort_cmp, NULL);
+
+        /*
+         * the first loop frees everything the leaves point to
+         */
+        for (i = 0; i < refi; i++) {
+                u64 ptr_gen;
+
+                bytenr = sorted[i].bytenr;
+
+                /*
+                 * check the reference count on this leaf.  If it is > 1
+                 * we just decrement it below and don't update any
+                 * of the refs the leaf points to.
+                 */
+                ret = drop_snap_lookup_refcount(root, bytenr, blocksize, &refs);
+                BUG_ON(ret);
+                if (refs != 1)
+                        continue;
+
+                ptr_gen = btrfs_node_ptr_generation(eb, sorted[i].slot);
+
+                /*
+                 * the leaf only had one reference, which means the
+                 * only thing pointing to this leaf is the snapshot
+                 * we're deleting.  It isn't possible for the reference
+                 * count to increase again later
+                 *
+                 * The reference cache is checked for the leaf,
+                 * and if found we'll be able to drop any refs held by
+                 * the leaf without needing to read it in.
+                 */
+                ref = btrfs_lookup_leaf_ref(root, bytenr);
+                if (ref && ref->generation != ptr_gen) {
+                        btrfs_free_leaf_ref(root, ref);
+                        ref = NULL;
+                }
+                if (ref) {
+                        ret = cache_drop_leaf_ref(trans, root, ref);
+                        BUG_ON(ret);
+                        btrfs_remove_leaf_ref(root, ref);
+                        btrfs_free_leaf_ref(root, ref);
+                } else {
+                        /*
+                         * the leaf wasn't in the reference cache, so
+                         * we have to read it.
+                         */
+                        leaf = read_tree_block(root, bytenr, blocksize,
+                                               ptr_gen);
+                        ret = btrfs_drop_leaf_ref(trans, root, leaf);
+                        BUG_ON(ret);
+                        free_extent_buffer(leaf);
+                }
+                atomic_inc(&root->fs_info->throttle_gen);
+                wake_up(&root->fs_info->transaction_throttle);
+                cond_resched();
+        }
+
+        /*
+         * run through the loop again to free the refs on the leaves.
+         * This is faster than doing it in the loop above because
+         * the leaves are likely to be clustered together.  We end up
+         * working in nice chunks on the extent allocation tree.
+         */
+        for (i = 0; i < refi; i++) {
+                bytenr = sorted[i].bytenr;
+                ret = __btrfs_free_extent(trans, root, bytenr,
+                                        blocksize, eb->start,
+                                        root_owner, root_gen, 0, 1);
+                BUG_ON(ret);
+
+                atomic_inc(&root->fs_info->throttle_gen);
+                wake_up(&root->fs_info->transaction_throttle);
+                cond_resched();
+        }
+out:
+        kfree(sorted);
+
+        /*
+         * update the path to show we've processed the entire level 1
+         * node.  This will get saved into the root's drop_snapshot_progress
+         * field so these drops are not repeated again if this transaction
+         * commits.
+         */
+        path->slots[1] = nritems;
+        return 0;
+}
+
+/*
  * helper function for drop_snapshot, this walks down the tree dropping ref
  * counts as it goes.
  */
@@ -3580,7 +3786,6 @@ static noinline int walk_down_tree(struct btrfs_trans_handle *trans,
         struct extent_buffer *next;
         struct extent_buffer *cur;
         struct extent_buffer *parent;
-        struct btrfs_leaf_ref *ref;
         u32 blocksize;
         int ret;
         u32 refs;
@@ -3607,17 +3812,46 @@ static noinline int walk_down_tree(struct btrfs_trans_handle *trans,
                 if (path->slots[*level] >=
                     btrfs_header_nritems(cur))
                         break;
+
+                /* the new code goes down to level 1 and does all the
+                 * leaves pointed to that node in bulk.  So, this check
+                 * for level 0 will always be false.
+                 *
+                 * But, the disk format allows the drop_snapshot_progress
+                 * field in the root to leave things in a state where
+                 * a leaf will need cleaning up here.  If someone crashes
+                 * with the old code and then boots with the new code,
+                 * we might find a leaf here.
+                 */
                 if (*level == 0) {
                         ret = btrfs_drop_leaf_ref(trans, root, cur);
                         BUG_ON(ret);
                         break;
                 }
+
+                /*
+                 * once we get to level one, process the whole node
+                 * at once, including everything below it.
+                 */
+                if (*level == 1) {
+                        ret = drop_level_one_refs(trans, root, path);
+                        BUG_ON(ret);
+                        break;
+                }
+
                 bytenr = btrfs_node_blockptr(cur, path->slots[*level]);
                 ptr_gen = btrfs_node_ptr_generation(cur, path->slots[*level]);
                 blocksize = btrfs_level_size(root, *level - 1);
 
                 ret = drop_snap_lookup_refcount(root, bytenr, blocksize, &refs);
                 BUG_ON(ret);
+
+                /*
+                 * if there is more than one reference, we don't need
+                 * to read that node to drop any references it has.  We
+                 * just drop the ref we hold on that node and move on to the
+                 * next slot in this level.
+                 */
                 if (refs != 1) {
                         parent = path->nodes[*level];
                         root_owner = btrfs_header_owner(parent);
@@ -3636,46 +3870,12 @@ static noinline int walk_down_tree(struct btrfs_trans_handle *trans,
 
                         continue;
                 }
+
                 /*
-                 * at this point, we have a single ref, and since the
-                 * only place referencing this extent is a dead root
-                 * the reference count should never go higher.
-                 * So, we don't need to check it again
+                 * we need to keep freeing things in the next level down.
+                 * read the block and loop around to process it
                  */
-                if (*level == 1) {
-                        ref = btrfs_lookup_leaf_ref(root, bytenr);
-                        if (ref && ref->generation != ptr_gen) {
-                                btrfs_free_leaf_ref(root, ref);
-                                ref = NULL;
-                        }
-                        if (ref) {
-                                ret = cache_drop_leaf_ref(trans, root, ref);
-                                BUG_ON(ret);
-                                btrfs_remove_leaf_ref(root, ref);
-                                btrfs_free_leaf_ref(root, ref);
-                                *level = 0;
-                                break;
-                        }
-                }
-                next = btrfs_find_tree_block(root, bytenr, blocksize);
-                if (!next || !btrfs_buffer_uptodate(next, ptr_gen)) {
-                        free_extent_buffer(next);
-
-                        next = read_tree_block(root, bytenr, blocksize,
-                                               ptr_gen);
-                        cond_resched();
-#if 0
-                        /*
-                         * this is a debugging check and can go away
-                         * the ref should never go all the way down to 1
-                         * at this point
-                         */
-                        ret = lookup_extent_ref(NULL, root, bytenr, blocksize,
-                                                &refs);
-                        BUG_ON(ret);
-                        WARN_ON(refs != 1);
-#endif
-                }
+                next = read_tree_block(root, bytenr, blocksize, ptr_gen);
                 WARN_ON(*level <= 0);
                 if (path->nodes[*level-1])
                         free_extent_buffer(path->nodes[*level-1]);
@@ -3700,11 +3900,16 @@ out:
         root_owner = btrfs_header_owner(parent);
         root_gen = btrfs_header_generation(parent);
 
+        /*
+         * cleanup and free the reference on the last node
+         * we processed
+         */
         ret = __btrfs_free_extent(trans, root, bytenr, blocksize,
                                   parent->start, root_owner, root_gen,
                                   *level, 1);
         free_extent_buffer(path->nodes[*level]);
         path->nodes[*level] = NULL;
+
         *level += 1;
         BUG_ON(ret);
 
@@ -3824,6 +4029,13 @@ static noinline int walk_up_tree(struct btrfs_trans_handle *trans,
                 if (slot < btrfs_header_nritems(path->nodes[i]) - 1) {
                         struct extent_buffer *node;
                         struct btrfs_disk_key disk_key;
+
+                        /*
+                         * there is more work to do in this level.
+                         * Update the drop_progress marker to reflect
+                         * the work we've done so far, and then bump
+                         * the slot number
+                         */
                         node = path->nodes[i];
                         path->slots[i]++;
                         *level = i;
@@ -3835,6 +4047,11 @@ static noinline int walk_up_tree(struct btrfs_trans_handle *trans,
                         return 0;
                 } else {
                         struct extent_buffer *parent;
+
+                        /*
+                         * this whole node is done, free our reference
+                         * on it and go up one level
+                         */
                         if (path->nodes[*level] == root->node)
                                 parent = path->nodes[*level];
                         else
@@ -4849,6 +5066,7 @@ int btrfs_reloc_tree_cache_ref(struct btrfs_trans_handle *trans,
                 ref->bytenr = buf->start;
                 ref->owner = btrfs_header_owner(buf);
                 ref->generation = btrfs_header_generation(buf);
+
                 ret = btrfs_add_leaf_ref(root, ref, 0);
                 WARN_ON(ret);
                 btrfs_free_leaf_ref(root, ref);
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index ebd7d6c37df8..95ea58cb3065 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -2441,6 +2441,8 @@ next_node:
                         ref->generation = leaf_gen;
                         ref->nritems = 0;
 
+                        btrfs_sort_leaf_ref(ref);
+
                         ret = btrfs_add_leaf_ref(root, ref, 0);
                         WARN_ON(ret);
                         btrfs_free_leaf_ref(root, ref);
diff --git a/fs/btrfs/ref-cache.c b/fs/btrfs/ref-cache.c
index 6f0acc4c9eab..d0cc62bccb94 100644
--- a/fs/btrfs/ref-cache.c
+++ b/fs/btrfs/ref-cache.c
@@ -17,6 +17,7 @@
  */
 
 #include <linux/sched.h>
+#include <linux/sort.h>
 #include "ctree.h"
 #include "ref-cache.h"
 #include "transaction.h"
diff --git a/fs/btrfs/ref-cache.h b/fs/btrfs/ref-cache.h
index 16f3183d7c59..bc283ad2db73 100644
--- a/fs/btrfs/ref-cache.h
+++ b/fs/btrfs/ref-cache.h
@@ -73,5 +73,4 @@ int btrfs_add_leaf_ref(struct btrfs_root *root, struct btrfs_leaf_ref *ref,
 int btrfs_remove_leaf_refs(struct btrfs_root *root, u64 max_root_gen,
                            int shared);
 int btrfs_remove_leaf_ref(struct btrfs_root *root, struct btrfs_leaf_ref *ref);
-
 #endif