Btrfs: update nodatacow code v2

This patch simplifies the nodatacow checker. If all references
were created after the latest snapshot, then we can avoid COW
safely. This patch also updates run_delalloc_nocow to do more
fine-grained checking.

Signed-off-by: Yan Zheng <zheng.yan@oracle.com>

7 files changed, 154 insertions, 213 deletions

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index ca5547af6090..8bf6a085a730 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -454,6 +454,7 @@ struct btrfs_root_item {
         __le64 bytenr;
         __le64 byte_limit;
         __le64 bytes_used;
+        __le64 last_snapshot;
         __le32 flags;
         __le32 refs;
         struct btrfs_disk_key drop_progress;
@@ -1413,6 +1414,8 @@ BTRFS_SETGET_STACK_FUNCS(root_refs, struct btrfs_root_item, refs, 32);
 BTRFS_SETGET_STACK_FUNCS(root_flags, struct btrfs_root_item, flags, 32);
 BTRFS_SETGET_STACK_FUNCS(root_used, struct btrfs_root_item, bytes_used, 64);
 BTRFS_SETGET_STACK_FUNCS(root_limit, struct btrfs_root_item, byte_limit, 64);
+BTRFS_SETGET_STACK_FUNCS(root_last_snapshot, struct btrfs_root_item,
+                         last_snapshot, 64);
 
 /* struct btrfs_super_block */
 BTRFS_SETGET_STACK_FUNCS(super_bytenr, struct btrfs_super_block, bytenr, 64);
@@ -1564,9 +1567,8 @@ int btrfs_update_pinned_extents(struct btrfs_root *root,
                                 u64 bytenr, u64 num, int pin);
 int btrfs_drop_leaf_ref(struct btrfs_trans_handle *trans,
                         struct btrfs_root *root, struct extent_buffer *leaf);
-int btrfs_cross_ref_exists(struct btrfs_trans_handle *trans,
-                           struct btrfs_root *root,
-                           struct btrfs_key *key, u64 bytenr);
+int btrfs_cross_ref_exist(struct btrfs_trans_handle *trans,
+                          struct btrfs_root *root, u64 bytenr);
 int btrfs_extent_post_op(struct btrfs_trans_handle *trans,
                          struct btrfs_root *root);
 int btrfs_copy_pinned(struct btrfs_root *root, struct extent_io_tree *copy);
diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 535cee47fcfb..1eb69a91b727 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -848,9 +848,8 @@ out:
         return 0;
 }
 
-static int get_reference_status(struct btrfs_root *root, u64 bytenr,
-                                u64 parent_gen, u64 ref_objectid,
-                                u64 *min_generation, u32 *ref_count)
+int btrfs_cross_ref_exist(struct btrfs_trans_handle *trans,
+                          struct btrfs_root *root, u64 bytenr)
 {
         struct btrfs_root *extent_root = root->fs_info->extent_root;
         struct btrfs_path *path;
@@ -858,8 +857,8 @@ static int get_reference_status(struct btrfs_root *root, u64 bytenr,
         struct btrfs_extent_ref *ref_item;
         struct btrfs_key key;
         struct btrfs_key found_key;
-        u64 root_objectid = root->root_key.objectid;
-        u64 ref_generation;
+        u64 ref_root;
+        u64 last_snapshot;
         u32 nritems;
         int ret;
 
@@ -872,7 +871,9 @@ static int get_reference_status(struct btrfs_root *root, u64 bytenr,
         if (ret < 0)
                 goto out;
         BUG_ON(ret == 0);
-        if (ret < 0 || path->slots[0] == 0)
+
+        ret = -ENOENT;
+        if (path->slots[0] == 0)
                 goto out;
 
         path->slots[0]--;
@@ -880,14 +881,10 @@ static int get_reference_status(struct btrfs_root *root, u64 bytenr,
         btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
 
         if (found_key.objectid != bytenr ||
-            found_key.type != BTRFS_EXTENT_ITEM_KEY) {
-                ret = 1;
+            found_key.type != BTRFS_EXTENT_ITEM_KEY)
                 goto out;
-        }
-
-        *ref_count = 0;
-        *min_generation = (u64)-1;
 
+        last_snapshot = btrfs_root_last_snapshot(&root->root_item);
         while (1) {
                 leaf = path->nodes[0];
                 nritems = btrfs_header_nritems(leaf);
@@ -910,114 +907,22 @@ static int get_reference_status(struct btrfs_root *root, u64 bytenr,
 
                 ref_item = btrfs_item_ptr(leaf, path->slots[0],
                                           struct btrfs_extent_ref);
-                ref_generation = btrfs_ref_generation(leaf, ref_item);
-                /*
-                 * For (parent_gen > 0 && parent_gen > ref_generation):
-                 *
-                 * we reach here through the oldest root, therefore
-                 * all other reference from same snapshot should have
-                 * a larger generation.
-                 */
-                if ((root_objectid != btrfs_ref_root(leaf, ref_item)) ||
-                    (parent_gen > 0 && parent_gen > ref_generation) ||
-                    (ref_objectid >= BTRFS_FIRST_FREE_OBJECTID &&
-                     ref_objectid != btrfs_ref_objectid(leaf, ref_item))) {
-                        *ref_count = 2;
-                        break;
-                }
-
-                *ref_count = 1;
-                if (*min_generation > ref_generation)
-                        *min_generation = ref_generation;
-
-                path->slots[0]++;
-        }
-        ret = 0;
-out:
-        btrfs_free_path(path);
-        return ret;
-}
-
-int btrfs_cross_ref_exists(struct btrfs_trans_handle *trans,
-                           struct btrfs_root *root,
-                           struct btrfs_key *key, u64 bytenr)
-{
-        struct btrfs_root *old_root;
-        struct btrfs_path *path = NULL;
-        struct extent_buffer *eb;
-        struct btrfs_file_extent_item *item;
-        u64 ref_generation;
-        u64 min_generation;
-        u64 extent_start;
-        u32 ref_count;
-        int level;
-        int ret;
-
-        BUG_ON(trans == NULL);
-        BUG_ON(key->type != BTRFS_EXTENT_DATA_KEY);
-        ret = get_reference_status(root, bytenr, 0, key->objectid,
-                                   &min_generation, &ref_count);
-        if (ret)
-                return ret;
-
-        if (ref_count != 1)
-                return 1;
-
-        old_root = root->dirty_root->root;
-        ref_generation = old_root->root_key.offset;
-
-        /* all references are created in running transaction */
-        if (min_generation > ref_generation) {
-                ret = 0;
-                goto out;
-        }
-
-        path = btrfs_alloc_path();
-        if (!path) {
-                ret = -ENOMEM;
-                goto out;
-        }
-
-        path->skip_locking = 1;
-        /* if no item found, the extent is referenced by other snapshot */
-        ret = btrfs_search_slot(NULL, old_root, key, path, 0, 0);
-        if (ret)
-                goto out;
-
-        eb = path->nodes[0];
-        item = btrfs_item_ptr(eb, path->slots[0],
-                              struct btrfs_file_extent_item);
-        if (btrfs_file_extent_type(eb, item) != BTRFS_FILE_EXTENT_REG ||
-            btrfs_file_extent_disk_bytenr(eb, item) != bytenr) {
-                ret = 1;
-                goto out;
-        }
-
-        for (level = BTRFS_MAX_LEVEL - 1; level >= -1; level--) {
-                if (level >= 0) {
-                        eb = path->nodes[level];
-                        if (!eb)
-                                continue;
-                        extent_start = eb->start;
-                } else
-                        extent_start = bytenr;
-
-                ret = get_reference_status(root, extent_start, ref_generation,
-                                           0, &min_generation, &ref_count);
-                if (ret)
+                ref_root = btrfs_ref_root(leaf, ref_item);
+                if (ref_root != root->root_key.objectid &&
+                    ref_root != BTRFS_TREE_LOG_OBJECTID) {
+                        ret = 1;
                         goto out;
-
-                if (ref_count != 1) {
+                }
+                if (btrfs_ref_generation(leaf, ref_item) <= last_snapshot) {
                         ret = 1;
                         goto out;
                 }
-                if (level >= 0)
-                        ref_generation = btrfs_header_generation(eb);
+
+                path->slots[0]++;
         }
         ret = 0;
 out:
-        if (path)
-                btrfs_free_path(path);
+        btrfs_free_path(path);
         return ret;
 }
 
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index e8511d14b119..3e6f0568fdb4 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -298,6 +298,7 @@ static int cow_file_range(struct inode *inode, struct page *locked_page,
         unsigned long max_compressed = 128 * 1024;
         unsigned long max_uncompressed = 256 * 1024;
         int i;
+        int ordered_type;
         int will_compress;
 
         trans = btrfs_join_transaction(root, 1);
@@ -491,9 +492,10 @@ again:
                 }
 
                 cur_alloc_size = ins.offset;
+                ordered_type = will_compress ? BTRFS_ORDERED_COMPRESSED : 0;
                 ret = btrfs_add_ordered_extent(inode, start, ins.objectid,
-                                               ram_size, cur_alloc_size, 0,
-                                               will_compress);
+                                               ram_size, cur_alloc_size,
+                                               ordered_type);
                 BUG_ON(ret);
 
                 if (disk_num_bytes < cur_alloc_size) {
@@ -587,115 +589,148 @@ free_pages_out:
 static int run_delalloc_nocow(struct inode *inode, struct page *locked_page,
                               u64 start, u64 end, int *page_started)
 {
-        u64 extent_start;
-        u64 extent_end;
-        u64 bytenr;
-        u64 loops = 0;
-        u64 total_fs_bytes;
         struct btrfs_root *root = BTRFS_I(inode)->root;
-        struct btrfs_block_group_cache *block_group;
         struct btrfs_trans_handle *trans;
         struct extent_buffer *leaf;
-        int found_type;
         struct btrfs_path *path;
-        struct btrfs_file_extent_item *item;
-        int ret;
-        int err = 0;
+        struct btrfs_file_extent_item *fi;
         struct btrfs_key found_key;
+        u64 cow_start;
+        u64 cur_offset;
+        u64 extent_end;
+        u64 disk_bytenr;
+        u64 num_bytes;
+        int extent_type;
+        int ret;
+        int nocow;
+        int check_prev = 1;
 
-        total_fs_bytes = btrfs_super_total_bytes(&root->fs_info->super_copy);
         path = btrfs_alloc_path();
         BUG_ON(!path);
         trans = btrfs_join_transaction(root, 1);
         BUG_ON(!trans);
-again:
-        ret = btrfs_lookup_file_extent(NULL, root, path,
-                                       inode->i_ino, start, 0);
-        if (ret < 0) {
-                err = ret;
-                goto out;
-        }
-
-        if (ret != 0) {
-                if (path->slots[0] == 0)
-                        goto not_found;
-                path->slots[0]--;
-        }
-
-        leaf = path->nodes[0];
-        item = btrfs_item_ptr(leaf, path->slots[0],
-                              struct btrfs_file_extent_item);
-
-        /* are we inside the extent that was found? */
-        btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
-        found_type = btrfs_key_type(&found_key);
-        if (found_key.objectid != inode->i_ino ||
-            found_type != BTRFS_EXTENT_DATA_KEY)
-                goto not_found;
-
-        found_type = btrfs_file_extent_type(leaf, item);
-        extent_start = found_key.offset;
-        if (found_type == BTRFS_FILE_EXTENT_REG) {
-                u64 extent_num_bytes;
-
-                extent_num_bytes = btrfs_file_extent_num_bytes(leaf, item);
-                extent_end = extent_start + extent_num_bytes;
-                err = 0;
 
-                if (btrfs_file_extent_compression(leaf, item) ||
-                    btrfs_file_extent_encryption(leaf,item) ||
-                    btrfs_file_extent_other_encoding(leaf, item))
-                        goto not_found;
+        cow_start = (u64)-1;
+        cur_offset = start;
+        while (1) {
+                ret = btrfs_lookup_file_extent(trans, root, path, inode->i_ino,
+                                               cur_offset, 0);
+                BUG_ON(ret < 0);
+                if (ret > 0 && path->slots[0] > 0 && check_prev) {
+                        leaf = path->nodes[0];
+                        btrfs_item_key_to_cpu(leaf, &found_key,
+                                              path->slots[0] - 1);
+                        if (found_key.objectid == inode->i_ino &&
+                            found_key.type == BTRFS_EXTENT_DATA_KEY)
+                                path->slots[0]--;
+                }
+                check_prev = 0;
+next_slot:
+                leaf = path->nodes[0];
+                if (path->slots[0] >= btrfs_header_nritems(leaf)) {
+                        ret = btrfs_next_leaf(root, path);
+                        if (ret < 0)
+                                BUG_ON(1);
+                        if (ret > 0)
+                                break;
+                        leaf = path->nodes[0];
+                }
 
-                if (loops && start != extent_start)
-                        goto not_found;
+                nocow = 0;
+                disk_bytenr = 0;
+                btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
 
-                if (start < extent_start || start >= extent_end)
-                        goto not_found;
+                if (found_key.objectid > inode->i_ino ||
+                    found_key.type > BTRFS_EXTENT_DATA_KEY ||
+                    found_key.offset > end)
+                        break;
 
-                bytenr = btrfs_file_extent_disk_bytenr(leaf, item);
-                if (bytenr == 0)
-                        goto not_found;
+                if (found_key.offset > cur_offset) {
+                        extent_end = found_key.offset;
+                        goto out_check;
+                }
 
-                if (btrfs_cross_ref_exists(trans, root, &found_key, bytenr))
-                        goto not_found;
-                /*
-                 * we may be called by the resizer, make sure we're inside
-                 * the limits of the FS
-                 */
-                block_group = btrfs_lookup_block_group(root->fs_info,
-                                                       bytenr);
-                if (!block_group || block_group->ro)
-                        goto not_found;
+                fi = btrfs_item_ptr(leaf, path->slots[0],
+                                    struct btrfs_file_extent_item);
+                extent_type = btrfs_file_extent_type(leaf, fi);
 
-                bytenr += btrfs_file_extent_offset(leaf, item);
-                extent_num_bytes = min(end + 1, extent_end) - start;
-                ret = btrfs_add_ordered_extent(inode, start, bytenr,
-                                                extent_num_bytes,
-                                                extent_num_bytes, 1, 0);
-                if (ret) {
-                        err = ret;
-                        goto out;
+                if (extent_type == BTRFS_FILE_EXTENT_REG) {
+                        struct btrfs_block_group_cache *block_group;
+                        disk_bytenr = btrfs_file_extent_disk_bytenr(leaf, fi);
+                        extent_end = found_key.offset +
+                                btrfs_file_extent_num_bytes(leaf, fi);
+                        if (extent_end <= start) {
+                                path->slots[0]++;
+                                goto next_slot;
+                        }
+                        if (btrfs_file_extent_compression(leaf, fi) ||
+                            btrfs_file_extent_encryption(leaf, fi) ||
+                            btrfs_file_extent_other_encoding(leaf, fi))
+                                goto out_check;
+                        if (disk_bytenr == 0)
+                                goto out_check;
+                        if (btrfs_cross_ref_exist(trans, root, disk_bytenr))
+                                goto out_check;
+                        block_group = btrfs_lookup_block_group(root->fs_info,
+                                                               disk_bytenr);
+                        if (!block_group || block_group->ro)
+                                goto out_check;
+                        disk_bytenr += btrfs_file_extent_offset(leaf, fi);
+                        nocow = 1;
+                } else if (extent_type == BTRFS_FILE_EXTENT_INLINE) {
+                        extent_end = found_key.offset +
+                                btrfs_file_extent_inline_len(leaf, fi);
+                        extent_end = ALIGN(extent_end, root->sectorsize);
+                } else {
+                        BUG_ON(1);
+                }
+out_check:
+                if (extent_end <= start) {
+                        path->slots[0]++;
+                        goto next_slot;
+                }
+                if (!nocow) {
+                        if (cow_start == (u64)-1)
+                                cow_start = cur_offset;
+                        cur_offset = extent_end;
+                        if (cur_offset > end)
+                                break;
+                        path->slots[0]++;
+                        goto next_slot;
                 }
 
                 btrfs_release_path(root, path);
-                start = extent_end;
-                if (start <= end) {
-                        loops++;
-                        goto again;
+                if (cow_start != (u64)-1) {
+                        ret = cow_file_range(inode, locked_page, cow_start,
+                                        found_key.offset - 1, page_started);
+                        BUG_ON(ret);
+                        cow_start = (u64)-1;
                 }
-        } else {
-not_found:
-                btrfs_end_transaction(trans, root);
-                btrfs_free_path(path);
-                return cow_file_range(inode, locked_page, start, end,
-                                      page_started);
+
+                disk_bytenr += cur_offset - found_key.offset;
+                num_bytes = min(end + 1, extent_end) - cur_offset;
+
+                ret = btrfs_add_ordered_extent(inode, cur_offset, disk_bytenr,
+                                               num_bytes, num_bytes,
+                                               BTRFS_ORDERED_NOCOW);
+                cur_offset = extent_end;
+                if (cur_offset > end)
+                        break;
         }
-out:
-        WARN_ON(err);
-        btrfs_end_transaction(trans, root);
+        btrfs_release_path(root, path);
+
+        if (cur_offset <= end && cow_start == (u64)-1)
+                cow_start = cur_offset;
+        if (cow_start != (u64)-1) {
+                ret = cow_file_range(inode, locked_page, cow_start, end,
+                                     page_started);
+                BUG_ON(ret);
+        }
+
+        ret = btrfs_end_transaction(trans, root);
+        BUG_ON(ret);
         btrfs_free_path(path);
-        return err;
+        return 0;
 }
 
 /*
diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index fd3c8b5676c1..7f915d478399 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -112,6 +112,7 @@ static noinline int create_subvol(struct btrfs_root *root,
         btrfs_set_root_level(&root_item, 0);
         btrfs_set_root_refs(&root_item, 1);
         btrfs_set_root_used(&root_item, 0);
+        btrfs_set_root_last_snapshot(&root_item, 0);
 
         memset(&root_item.drop_progress, 0, sizeof(root_item.drop_progress));
         root_item.drop_level = 0;
diff --git a/fs/btrfs/ordered-data.c b/fs/btrfs/ordered-data.c
index b5745bb96d40..e7317c8fda29 100644
--- a/fs/btrfs/ordered-data.c
+++ b/fs/btrfs/ordered-data.c
@@ -165,8 +165,7 @@ static inline struct rb_node *tree_search(struct btrfs_ordered_inode_tree *tree,
  * inserted.
  */
 int btrfs_add_ordered_extent(struct inode *inode, u64 file_offset,
-                             u64 start, u64 len, u64 disk_len, int nocow,
-                             int compressed)
+                             u64 start, u64 len, u64 disk_len, int type)
 {
         struct btrfs_ordered_inode_tree *tree;
         struct rb_node *node;
@@ -183,10 +182,8 @@ int btrfs_add_ordered_extent(struct inode *inode, u64 file_offset,
         entry->len = len;
         entry->disk_len = disk_len;
         entry->inode = inode;
-        if (nocow)
-                set_bit(BTRFS_ORDERED_NOCOW, &entry->flags);
-        if (compressed)
-                set_bit(BTRFS_ORDERED_COMPRESSED, &entry->flags);
+        if (type == BTRFS_ORDERED_NOCOW || type == BTRFS_ORDERED_COMPRESSED)
+                set_bit(type, &entry->flags);
 
         /* one ref for the tree */
         atomic_set(&entry->refs, 1);
diff --git a/fs/btrfs/ordered-data.h b/fs/btrfs/ordered-data.h
index 1ef464145d22..e6d9bc54c2b1 100644
--- a/fs/btrfs/ordered-data.h
+++ b/fs/btrfs/ordered-data.h
@@ -132,8 +132,7 @@ int btrfs_remove_ordered_extent(struct inode *inode,
 int btrfs_dec_test_ordered_pending(struct inode *inode,
                                        u64 file_offset, u64 io_size);
 int btrfs_add_ordered_extent(struct inode *inode, u64 file_offset,
-                             u64 start, u64 len, u64 disk_len, int nocow,
-                             int compressed);
+                             u64 start, u64 len, u64 disk_len, int type);
 int btrfs_add_ordered_sum(struct inode *inode,
                           struct btrfs_ordered_extent *entry,
                           struct btrfs_ordered_sum *sum);
diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c
index 968b84f17a19..e72a013d24bf 100644
--- a/fs/btrfs/transaction.c
+++ b/fs/btrfs/transaction.c
@@ -763,6 +763,8 @@ static noinline int create_pending_snapshot(struct btrfs_trans_handle *trans,
         if (ret)
                 goto fail;
 
+        btrfs_record_root_in_trans(root);
+        btrfs_set_root_last_snapshot(&root->root_item, trans->transid);
         memcpy(new_root_item, &root->root_item, sizeof(*new_root_item));
 
         key.objectid = objectid;