Btrfs: Add btree locking to the tree defragmentation code

The online btree defragger is simplified and rewritten to use
standard btree searches instead of a walk up / down mechanism.

Signed-off-by: Chris Mason <chris.mason@oracle.com>

4 files changed, 93 insertions, 201 deletions

diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c
index 40f0e0cb804b..7f4cc2b88d09 100644
--- a/fs/btrfs/ctree.c
+++ b/fs/btrfs/ctree.c
@@ -354,7 +354,6 @@ int btrfs_realloc_node(struct btrfs_trans_handle *trans,
                        struct btrfs_key *progress)
 {
         struct extent_buffer *cur;
-        struct extent_buffer *tmp;
         u64 blocknr;
         u64 gen;
         u64 search_start = *last_ret;
@@ -370,9 +369,6 @@ int btrfs_realloc_node(struct btrfs_trans_handle *trans,
         int progress_passed = 0;
         struct btrfs_disk_key disk_key;
 
-        /* FIXME this code needs locking */
-        return 0;
-
         parent_level = btrfs_header_level(parent);
         if (cache_only && parent_level != 1)
                 return 0;
@@ -454,20 +450,23 @@ int btrfs_realloc_node(struct btrfs_trans_handle *trans,
                 if (search_start == 0)
                         search_start = last_block;
 
+                btrfs_tree_lock(cur);
                 err = __btrfs_cow_block(trans, root, cur, parent, i,
-                                        &tmp, search_start,
+                                        &cur, search_start,
                                         min(16 * blocksize,
                                             (end_slot - i) * blocksize));
                 if (err) {
+                        btrfs_tree_unlock(cur);
                         free_extent_buffer(cur);
                         break;
                 }
-                search_start = tmp->start;
-                last_block = tmp->start;
+                search_start = cur->start;
+                last_block = cur->start;
                 *last_ret = search_start;
                 if (parent_level == 1)
-                        btrfs_clear_buffer_defrag(tmp);
-                free_extent_buffer(tmp);
+                        btrfs_clear_buffer_defrag(cur);
+                btrfs_tree_unlock(cur);
+                free_extent_buffer(cur);
         }
         if (parent->map_token) {
                 unmap_extent_buffer(parent, parent->map_token,
@@ -2970,6 +2969,35 @@ int btrfs_prev_leaf(struct btrfs_root *root, struct btrfs_path *path)
         return 1;
 }
 
+int btrfs_find_next_key(struct btrfs_root *root, struct btrfs_path *path,
+                        struct btrfs_key *key, int lowest_level)
+{
+        int level = lowest_level;
+        int slot;
+        struct extent_buffer *c;
+
+        while(level < BTRFS_MAX_LEVEL) {
+                if (!path->nodes[level])
+                        return 1;
+
+                slot = path->slots[level] + 1;
+                c = path->nodes[level];
+                if (slot >= btrfs_header_nritems(c)) {
+                        level++;
+                        if (level == BTRFS_MAX_LEVEL) {
+                                return 1;
+                        }
+                        continue;
+                }
+                if (level == 0)
+                        btrfs_item_key_to_cpu(c, key, slot);
+                else
+                        btrfs_node_key_to_cpu(c, key, slot);
+                return 0;
+        }
+        return 1;
+}
+
 /*
  * search the tree again to find a leaf with greater keys
  * returns 0 if it found something or 1 if there are no greater leaves.
diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 244fe86bcc55..ca8e6f15859e 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -1411,6 +1411,8 @@ int btrfs_previous_item(struct btrfs_root *root,
 
 struct extent_buffer *btrfs_root_node(struct btrfs_root *root);
 struct extent_buffer *btrfs_lock_root_node(struct btrfs_root *root);
+int btrfs_find_next_key(struct btrfs_root *root, struct btrfs_path *path,
+                        struct btrfs_key *key, int lowest_level);
 
 int btrfs_cow_block(struct btrfs_trans_handle *trans,
                     struct btrfs_root *root, struct extent_buffer *buf,
diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 89cc4f611869..a9b3a25a45b7 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -2201,6 +2201,7 @@ int drop_snap_lookup_refcount(struct btrfs_root *root, u64 start, u64 len,
 {
         mutex_unlock(&root->fs_info->alloc_mutex);
         lookup_extent_ref(NULL, root, start, len, refs);
+        cond_resched();
         mutex_lock(&root->fs_info->alloc_mutex);
         return lookup_extent_ref(NULL, root, start, len, refs);
 }
@@ -2280,6 +2281,7 @@ static int noinline walk_down_tree(struct btrfs_trans_handle *trans,
 
                         next = read_tree_block(root, bytenr, blocksize,
                                                ptr_gen);
+                        cond_resched();
                         mutex_lock(&root->fs_info->alloc_mutex);
 
                         /* we've dropped the lock, double check */
@@ -2329,6 +2331,7 @@ out:
         *level += 1;
         BUG_ON(ret);
         mutex_unlock(&root->fs_info->alloc_mutex);
+        cond_resched();
         return 0;
 }
 
@@ -2448,6 +2451,10 @@ int btrfs_drop_snapshot(struct btrfs_trans_handle *trans, struct btrfs_root
                         break;
                 if (wret < 0)
                         ret = wret;
+                if (trans->transaction->in_commit) {
+                        ret = -EAGAIN;
+                        break;
+                }
         }
         for (i = 0; i <= orig_level; i++) {
                 if (path->nodes[i]) {
diff --git a/fs/btrfs/tree-defrag.c b/fs/btrfs/tree-defrag.c
index fab851d85383..1677e4edaf6f 100644
--- a/fs/btrfs/tree-defrag.c
+++ b/fs/btrfs/tree-defrag.c
@@ -21,167 +21,26 @@
 #include "disk-io.h"
 #include "print-tree.h"
 #include "transaction.h"
-
-static void reada_defrag(struct btrfs_root *root,
-                         struct extent_buffer *node)
-{
-        int i;
-        u32 nritems;
-        u64 bytenr;
-        u64 gen;
-        u32 blocksize;
-        int ret;
-
-        blocksize = btrfs_level_size(root, btrfs_header_level(node) - 1);
-        nritems = btrfs_header_nritems(node);
-        for (i = 0; i < nritems; i++) {
-                bytenr = btrfs_node_blockptr(node, i);
-                gen = btrfs_node_ptr_generation(node, i);
-                ret = readahead_tree_block(root, bytenr, blocksize, gen);
-                if (ret)
-                        break;
-        }
-}
-
-static int defrag_walk_down(struct btrfs_trans_handle *trans,
-                            struct btrfs_root *root,
-                            struct btrfs_path *path, int *level,
-                            int cache_only, u64 *last_ret)
-{
-        struct extent_buffer *next;
-        struct extent_buffer *cur;
-        u64 bytenr;
-        u64 ptr_gen;
-        int ret = 0;
-        int is_extent = 0;
-
-        WARN_ON(*level < 0);
-        WARN_ON(*level >= BTRFS_MAX_LEVEL);
-
-        if (root->fs_info->extent_root == root)
-                is_extent = 1;
-
-        if (*level == 1 && cache_only && path->nodes[1] &&
-            !btrfs_buffer_defrag(path->nodes[1])) {
-                goto out;
-        }
-        while(*level > 0) {
-                WARN_ON(*level < 0);
-                WARN_ON(*level >= BTRFS_MAX_LEVEL);
-                cur = path->nodes[*level];
-
-                if (!cache_only && *level > 1 && path->slots[*level] == 0)
-                        reada_defrag(root, cur);
-
-                if (btrfs_header_level(cur) != *level)
-                        WARN_ON(1);
-
-                if (path->slots[*level] >=
-                    btrfs_header_nritems(cur))
-                        break;
-
-                if (*level == 1) {
-                        WARN_ON(btrfs_header_generation(path->nodes[*level]) !=
-                                                        trans->transid);
-                        ret = btrfs_realloc_node(trans, root,
-                                                 path->nodes[*level],
-                                                 path->slots[*level],
-                                                 cache_only, last_ret,
-                                                 &root->defrag_progress);
-                        if (is_extent)
-                                btrfs_extent_post_op(trans, root);
-
-                        break;
-                }
-                bytenr = btrfs_node_blockptr(cur, path->slots[*level]);
-                ptr_gen = btrfs_node_ptr_generation(cur, path->slots[*level]);
-
-                if (cache_only) {
-                        next = btrfs_find_tree_block(root, bytenr,
-                                           btrfs_level_size(root, *level - 1));
-                        if (!next || !btrfs_buffer_uptodate(next, ptr_gen) ||
-                            !btrfs_buffer_defrag(next)) {
-                                free_extent_buffer(next);
-                                path->slots[*level]++;
-                                continue;
-                        }
-                } else {
-                        next = read_tree_block(root, bytenr,
-                                       btrfs_level_size(root, *level - 1),
-                                       ptr_gen);
-                }
-                ret = btrfs_cow_block(trans, root, next, path->nodes[*level],
-                                      path->slots[*level], &next);
-                BUG_ON(ret);
-                if (is_extent)
-                        btrfs_extent_post_op(trans, root);
-
-                WARN_ON(*level <= 0);
-                if (path->nodes[*level-1])
-                        free_extent_buffer(path->nodes[*level-1]);
-                path->nodes[*level-1] = next;
-                *level = btrfs_header_level(next);
-                path->slots[*level] = 0;
-        }
-        WARN_ON(*level < 0);
-        WARN_ON(*level >= BTRFS_MAX_LEVEL);
-
-        btrfs_clear_buffer_defrag(path->nodes[*level]);
-out:
-        free_extent_buffer(path->nodes[*level]);
-        path->nodes[*level] = NULL;
-        *level += 1;
-        WARN_ON(ret && ret != -EAGAIN);
-        return ret;
-}
-
-static int defrag_walk_up(struct btrfs_trans_handle *trans,
-                          struct btrfs_root *root,
-                          struct btrfs_path *path, int *level,
-                          int cache_only)
-{
-        int i;
-        int slot;
-        struct extent_buffer *node;
-
-        for(i = *level; i < BTRFS_MAX_LEVEL - 1 && path->nodes[i]; i++) {
-                slot = path->slots[i];
-                if (slot < btrfs_header_nritems(path->nodes[i]) - 1) {
-                        path->slots[i]++;
-                        *level = i;
-                        node = path->nodes[i];
-                        WARN_ON(i == 0);
-                        btrfs_node_key_to_cpu(node, &root->defrag_progress,
-                                              path->slots[i]);
-                        root->defrag_level = i;
-                        return 0;
-                } else {
-                        btrfs_clear_buffer_defrag(path->nodes[*level]);
-                        free_extent_buffer(path->nodes[*level]);
-                        path->nodes[*level] = NULL;
-                        *level = i + 1;
-                }
-        }
-        return 1;
-}
+#include "locking.h"
 
 int btrfs_defrag_leaves(struct btrfs_trans_handle *trans,
                         struct btrfs_root *root, int cache_only)
 {
         struct btrfs_path *path = NULL;
-        struct extent_buffer *tmp;
+        struct btrfs_key key;
         int ret = 0;
         int wret;
         int level;
         int orig_level;
         int i;
         int is_extent = 0;
+        int next_key_ret = 0;
         u64 last_ret = 0;
 
-        if (root->fs_info->extent_root == root)
+        if (root->fs_info->extent_root == root) {
+                mutex_lock(&root->fs_info->alloc_mutex);
                 is_extent = 1;
-
-        goto out;
+        }
 
         if (root->ref_cows == 0 && !is_extent)
                 goto out;
@@ -200,67 +59,63 @@ int btrfs_defrag_leaves(struct btrfs_trans_handle *trans,
                 goto out;
         }
         if (root->defrag_progress.objectid == 0) {
+                struct extent_buffer *root_node;
                 u32 nritems;
 
-                nritems = btrfs_header_nritems(root->node);
+                root_node = btrfs_lock_root_node(root);
+                nritems = btrfs_header_nritems(root_node);
                 root->defrag_max.objectid = 0;
                 /* from above we know this is not a leaf */
-                btrfs_node_key_to_cpu(root->node, &root->defrag_max,
+                btrfs_node_key_to_cpu(root_node, &root->defrag_max,
                                       nritems - 1);
-                extent_buffer_get(root->node);
-                ret = btrfs_cow_block(trans, root, root->node, NULL, 0, &tmp);
-                BUG_ON(ret);
-                path->nodes[level] = root->node;
-                path->slots[level] = 0;
-                if (is_extent)
-                        btrfs_extent_post_op(trans, root);
+                btrfs_tree_unlock(root_node);
+                free_extent_buffer(root_node);
+                memset(&key, 0, sizeof(key));
         } else {
-                level = root->defrag_level;
-                path->lowest_level = level;
-                wret = btrfs_search_slot(trans, root, &root->defrag_progress,
-                                         path, 0, 1);
-
-                if (is_extent)
-                        btrfs_extent_post_op(trans, root);
-
-                if (wret < 0) {
-                        ret = wret;
-                        goto out;
-                }
-
-                while(level > 0 && !path->nodes[level])
-                        level--;
-
-                if (!path->nodes[level]) {
-                        ret = 0;
-                        goto out;
-                }
+                memcpy(&key, &root->defrag_progress, sizeof(key));
         }
 
-        while(1) {
-                wret = defrag_walk_down(trans, root, path, &level, cache_only,
-                                        &last_ret);
-                if (wret > 0)
-                        break;
-                if (wret < 0)
-                        ret = wret;
+        path->lowest_level = 1;
+        path->keep_locks = 1;
+        wret = btrfs_search_slot(trans, root, &key, path, 0, 1);
 
-                wret = defrag_walk_up(trans, root, path, &level, cache_only);
-                if (wret > 0)
-                        break;
-                if (wret < 0)
-                        ret = wret;
-                else
-                        ret = -EAGAIN;
-                break;
+        if (wret < 0) {
+                ret = wret;
+                goto out;
+        }
+        if (!path->nodes[1]) {
+                ret = 0;
+                goto out;
+        }
+        path->slots[1] = btrfs_header_nritems(path->nodes[1]);
+        next_key_ret = btrfs_find_next_key(root, path, &key, 1);
+        ret = btrfs_realloc_node(trans, root,
+                                 path->nodes[1], 0,
+                                 cache_only, &last_ret,
+                                 &root->defrag_progress);
+        WARN_ON(ret && ret != -EAGAIN);
+        if (next_key_ret == 0) {
+                memcpy(&root->defrag_progress, &key, sizeof(key));
+                ret = -EAGAIN;
         }
-        for (i = 0; i <= orig_level; i++) {
+
+        for (i = 1; i < BTRFS_MAX_LEVEL; i++) {
+                if (path->locks[i]) {
+                        btrfs_tree_unlock(path->nodes[i]);
+                        path->locks[i] = 0;
+                }
                 if (path->nodes[i]) {
                         free_extent_buffer(path->nodes[i]);
                         path->nodes[i] = NULL;
                 }
         }
+        if (is_extent)
+                btrfs_extent_post_op(trans, root);
+
 out:
+        if (is_extent)
+                mutex_unlock(&root->fs_info->alloc_mutex);
+
         if (path)
                 btrfs_free_path(path);
         if (ret == -EAGAIN) {