Btrfs: Integrate metadata reservation with start_transaction

Besides simplify the code, this change makes sure all metadata
reservation for normal metadata operations are released after
committing transaction.

Changes since V1:

Add code that check if unlink and rmdir will free space.

Add ENOSPC handling for clone ioctl.

Signed-off-by: Yan Zheng <zheng.yan@oracle.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>

1 files changed, 257 insertions, 146 deletions

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index f44425081c02..c4b0fd12df68 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -2135,7 +2135,7 @@ void btrfs_orphan_cleanup(struct btrfs_root *root)
                  * do a destroy_inode
                  */
                 if (is_bad_inode(inode)) {
-                        trans = btrfs_start_transaction(root, 1);
+                        trans = btrfs_start_transaction(root, 0);
                         btrfs_orphan_del(trans, inode);
                         btrfs_end_transaction(trans, root);
                         iput(inode);
@@ -2478,29 +2478,201 @@ out:
         return ret;
 }
 
-static int btrfs_unlink(struct inode *dir, struct dentry *dentry)
+/* helper to check if there is any shared block in the path */
+static int check_path_shared(struct btrfs_root *root,
+                             struct btrfs_path *path)
+{
+        struct extent_buffer *eb;
+        int level;
+        int ret;
+        u64 refs;
+
+        for (level = 0; level < BTRFS_MAX_LEVEL; level++) {
+                if (!path->nodes[level])
+                        break;
+                eb = path->nodes[level];
+                if (!btrfs_block_can_be_shared(root, eb))
+                        continue;
+                ret = btrfs_lookup_extent_info(NULL, root, eb->start, eb->len,
+                                               &refs, NULL);
+                if (refs > 1)
+                        return 1;
+        }
+        return 0;
+}
+
+/*
+ * helper to start transaction for unlink and rmdir.
+ *
+ * unlink and rmdir are special in btrfs, they do not always free space.
+ * so in enospc case, we should make sure they will free space before
+ * allowing them to use the global metadata reservation.
+ */
+static struct btrfs_trans_handle *__unlink_start_trans(struct inode *dir,
+                                                       struct dentry *dentry)
 {
-        struct btrfs_root *root;
         struct btrfs_trans_handle *trans;
+        struct btrfs_root *root = BTRFS_I(dir)->root;
+        struct btrfs_path *path;
+        struct btrfs_inode_ref *ref;
+        struct btrfs_dir_item *di;
         struct inode *inode = dentry->d_inode;
+        u64 index;
+        int check_link = 1;
+        int err = -ENOSPC;
         int ret;
-        unsigned long nr = 0;
 
-        root = BTRFS_I(dir)->root;
+        trans = btrfs_start_transaction(root, 10);
+        if (!IS_ERR(trans) || PTR_ERR(trans) != -ENOSPC)
+                return trans;
 
-        /*
-         * 5 items for unlink inode
-         * 1 for orphan
-         */
-        ret = btrfs_reserve_metadata_space(root, 6);
-        if (ret)
-                return ret;
+        if (inode->i_ino == BTRFS_EMPTY_SUBVOL_DIR_OBJECTID)
+                return ERR_PTR(-ENOSPC);
 
-        trans = btrfs_start_transaction(root, 1);
+        /* check if there is someone else holds reference */
+        if (S_ISDIR(inode->i_mode) && atomic_read(&inode->i_count) > 1)
+                return ERR_PTR(-ENOSPC);
+
+        if (atomic_read(&inode->i_count) > 2)
+                return ERR_PTR(-ENOSPC);
+
+        if (xchg(&root->fs_info->enospc_unlink, 1))
+                return ERR_PTR(-ENOSPC);
+
+        path = btrfs_alloc_path();
+        if (!path) {
+                root->fs_info->enospc_unlink = 0;
+                return ERR_PTR(-ENOMEM);
+        }
+
+        trans = btrfs_start_transaction(root, 0);
         if (IS_ERR(trans)) {
-                btrfs_unreserve_metadata_space(root, 6);
-                return PTR_ERR(trans);
+                btrfs_free_path(path);
+                root->fs_info->enospc_unlink = 0;
+                return trans;
+        }
+
+        path->skip_locking = 1;
+        path->search_commit_root = 1;
+
+        ret = btrfs_lookup_inode(trans, root, path,
+                                &BTRFS_I(dir)->location, 0);
+        if (ret < 0) {
+                err = ret;
+                goto out;
+        }
+        if (ret == 0) {
+                if (check_path_shared(root, path))
+                        goto out;
+        } else {
+                check_link = 0;
         }
+        btrfs_release_path(root, path);
+
+        ret = btrfs_lookup_inode(trans, root, path,
+                                &BTRFS_I(inode)->location, 0);
+        if (ret < 0) {
+                err = ret;
+                goto out;
+        }
+        if (ret == 0) {
+                if (check_path_shared(root, path))
+                        goto out;
+        } else {
+                check_link = 0;
+        }
+        btrfs_release_path(root, path);
+
+        if (ret == 0 && S_ISREG(inode->i_mode)) {
+                ret = btrfs_lookup_file_extent(trans, root, path,
+                                               inode->i_ino, (u64)-1, 0);
+                if (ret < 0) {
+                        err = ret;
+                        goto out;
+                }
+                BUG_ON(ret == 0);
+                if (check_path_shared(root, path))
+                        goto out;
+                btrfs_release_path(root, path);
+        }
+
+        if (!check_link) {
+                err = 0;
+                goto out;
+        }
+
+        di = btrfs_lookup_dir_item(trans, root, path, dir->i_ino,
+                                dentry->d_name.name, dentry->d_name.len, 0);
+        if (IS_ERR(di)) {
+                err = PTR_ERR(di);
+                goto out;
+        }
+        if (di) {
+                if (check_path_shared(root, path))
+                        goto out;
+        } else {
+                err = 0;
+                goto out;
+        }
+        btrfs_release_path(root, path);
+
+        ref = btrfs_lookup_inode_ref(trans, root, path,
+                                dentry->d_name.name, dentry->d_name.len,
+                                inode->i_ino, dir->i_ino, 0);
+        if (IS_ERR(ref)) {
+                err = PTR_ERR(ref);
+                goto out;
+        }
+        BUG_ON(!ref);
+        if (check_path_shared(root, path))
+                goto out;
+        index = btrfs_inode_ref_index(path->nodes[0], ref);
+        btrfs_release_path(root, path);
+
+        di = btrfs_lookup_dir_index_item(trans, root, path, dir->i_ino, index,
+                                dentry->d_name.name, dentry->d_name.len, 0);
+        if (IS_ERR(di)) {
+                err = PTR_ERR(di);
+                goto out;
+        }
+        BUG_ON(ret == -ENOENT);
+        if (check_path_shared(root, path))
+                goto out;
+
+        err = 0;
+out:
+        btrfs_free_path(path);
+        if (err) {
+                btrfs_end_transaction(trans, root);
+                root->fs_info->enospc_unlink = 0;
+                return ERR_PTR(err);
+        }
+
+        trans->block_rsv = &root->fs_info->global_block_rsv;
+        return trans;
+}
+
+static void __unlink_end_trans(struct btrfs_trans_handle *trans,
+                               struct btrfs_root *root)
+{
+        if (trans->block_rsv == &root->fs_info->global_block_rsv) {
+                BUG_ON(!root->fs_info->enospc_unlink);
+                root->fs_info->enospc_unlink = 0;
+        }
+        btrfs_end_transaction_throttle(trans, root);
+}
+
+static int btrfs_unlink(struct inode *dir, struct dentry *dentry)
+{
+        struct btrfs_root *root = BTRFS_I(dir)->root;
+        struct btrfs_trans_handle *trans;
+        struct inode *inode = dentry->d_inode;
+        int ret;
+        unsigned long nr = 0;
+
+        trans = __unlink_start_trans(dir, dentry);
+        if (IS_ERR(trans))
+                return PTR_ERR(trans);
 
         btrfs_set_trans_block_group(trans, dir);
 
@@ -2508,14 +2680,15 @@ static int btrfs_unlink(struct inode *dir, struct dentry *dentry)
 
         ret = btrfs_unlink_inode(trans, root, dir, dentry->d_inode,
                                  dentry->d_name.name, dentry->d_name.len);
+        BUG_ON(ret);
 
-        if (inode->i_nlink == 0)
+        if (inode->i_nlink == 0) {
                 ret = btrfs_orphan_add(trans, inode);
+                BUG_ON(ret);
+        }
 
         nr = trans->blocks_used;
-
-        btrfs_end_transaction_throttle(trans, root);
-        btrfs_unreserve_metadata_space(root, 6);
+        __unlink_end_trans(trans, root);
         btrfs_btree_balance_dirty(root, nr);
         return ret;
 }
@@ -2587,7 +2760,6 @@ static int btrfs_rmdir(struct inode *dir, struct dentry *dentry)
 {
         struct inode *inode = dentry->d_inode;
         int err = 0;
-        int ret;
         struct btrfs_root *root = BTRFS_I(dir)->root;
         struct btrfs_trans_handle *trans;
         unsigned long nr = 0;
@@ -2596,15 +2768,9 @@ static int btrfs_rmdir(struct inode *dir, struct dentry *dentry)
             inode->i_ino == BTRFS_FIRST_FREE_OBJECTID)
                 return -ENOTEMPTY;
 
-        ret = btrfs_reserve_metadata_space(root, 5);
-        if (ret)
-                return ret;
-
-        trans = btrfs_start_transaction(root, 1);
-        if (IS_ERR(trans)) {
-                btrfs_unreserve_metadata_space(root, 5);
+        trans = __unlink_start_trans(dir, dentry);
+        if (IS_ERR(trans))
                 return PTR_ERR(trans);
-        }
 
         btrfs_set_trans_block_group(trans, dir);
 
@@ -2627,12 +2793,9 @@ static int btrfs_rmdir(struct inode *dir, struct dentry *dentry)
                 btrfs_i_size_write(inode, 0);
 out:
         nr = trans->blocks_used;
-        ret = btrfs_end_transaction_throttle(trans, root);
-        btrfs_unreserve_metadata_space(root, 5);
+        __unlink_end_trans(trans, root);
         btrfs_btree_balance_dirty(root, nr);
 
-        if (ret && !err)
-                err = ret;
         return err;
 }
 
@@ -3145,7 +3308,7 @@ int btrfs_cont_expand(struct inode *inode, loff_t size)
         struct btrfs_trans_handle *trans;
         struct btrfs_root *root = BTRFS_I(inode)->root;
         struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree;
-        struct extent_map *em;
+        struct extent_map *em = NULL;
         struct extent_state *cached_state = NULL;
         u64 mask = root->sectorsize - 1;
         u64 hole_start = (inode->i_size + mask) & ~mask;
@@ -3183,11 +3346,11 @@ int btrfs_cont_expand(struct inode *inode, loff_t size)
                         u64 hint_byte = 0;
                         hole_size = last_byte - cur_offset;
 
-                        err = btrfs_reserve_metadata_space(root, 2);
-                        if (err)
+                        trans = btrfs_start_transaction(root, 2);
+                        if (IS_ERR(trans)) {
+                                err = PTR_ERR(trans);
                                 break;
-
-                        trans = btrfs_start_transaction(root, 1);
+                        }
                         btrfs_set_trans_block_group(trans, inode);
 
                         err = btrfs_drop_extents(trans, inode, cur_offset,
@@ -3205,14 +3368,15 @@ int btrfs_cont_expand(struct inode *inode, loff_t size)
                                         last_byte - 1, 0);
 
                         btrfs_end_transaction(trans, root);
-                        btrfs_unreserve_metadata_space(root, 2);
                 }
                 free_extent_map(em);
+                em = NULL;
                 cur_offset = last_byte;
                 if (cur_offset >= block_end)
                         break;
         }
 
+        free_extent_map(em);
         unlock_extent_cached(io_tree, hole_start, block_end - 1, &cached_state,
                              GFP_NOFS);
         return err;
@@ -3239,10 +3403,6 @@ static int btrfs_setattr_size(struct inode *inode, struct iattr *attr)
                 }
         }
 
-        ret = btrfs_reserve_metadata_space(root, 1);
-        if (ret)
-                return ret;
-
         trans = btrfs_start_transaction(root, 1);
         btrfs_set_trans_block_group(trans, inode);
 
@@ -3251,7 +3411,6 @@ static int btrfs_setattr_size(struct inode *inode, struct iattr *attr)
 
         nr = trans->blocks_used;
         btrfs_end_transaction(trans, root);
-        btrfs_unreserve_metadata_space(root, 1);
         btrfs_btree_balance_dirty(root, nr);
 
         if (attr->ia_size > inode->i_size) {
@@ -4223,26 +4382,21 @@ static int btrfs_mknod(struct inode *dir, struct dentry *dentry,
         if (!new_valid_dev(rdev))
                 return -EINVAL;
 
+        err = btrfs_find_free_objectid(NULL, root, dir->i_ino, &objectid);
+        if (err)
+                return err;
+
         /*
          * 2 for inode item and ref
          * 2 for dir items
          * 1 for xattr if selinux is on
          */
-        err = btrfs_reserve_metadata_space(root, 5);
-        if (err)
-                return err;
+        trans = btrfs_start_transaction(root, 5);
+        if (IS_ERR(trans))
+                return PTR_ERR(trans);
 
-        trans = btrfs_start_transaction(root, 1);
-        if (!trans)
-                goto fail;
         btrfs_set_trans_block_group(trans, dir);
 
-        err = btrfs_find_free_objectid(trans, root, dir->i_ino, &objectid);
-        if (err) {
-                err = -ENOSPC;
-                goto out_unlock;
-        }
-
         inode = btrfs_new_inode(trans, root, dir, dentry->d_name.name,
                                 dentry->d_name.len,
                                 dentry->d_parent->d_inode->i_ino, objectid,
@@ -4271,13 +4425,11 @@ static int btrfs_mknod(struct inode *dir, struct dentry *dentry,
 out_unlock:
         nr = trans->blocks_used;
         btrfs_end_transaction_throttle(trans, root);
-fail:
-        btrfs_unreserve_metadata_space(root, 5);
+        btrfs_btree_balance_dirty(root, nr);
         if (drop_inode) {
                 inode_dec_link_count(inode);
                 iput(inode);
         }
-        btrfs_btree_balance_dirty(root, nr);
         return err;
 }
 
@@ -4287,32 +4439,26 @@ static int btrfs_create(struct inode *dir, struct dentry *dentry,
         struct btrfs_trans_handle *trans;
         struct btrfs_root *root = BTRFS_I(dir)->root;
         struct inode *inode = NULL;
-        int err;
         int drop_inode = 0;
+        int err;
         unsigned long nr = 0;
         u64 objectid;
         u64 index = 0;
 
+        err = btrfs_find_free_objectid(NULL, root, dir->i_ino, &objectid);
+        if (err)
+                return err;
         /*
          * 2 for inode item and ref
          * 2 for dir items
          * 1 for xattr if selinux is on
          */
-        err = btrfs_reserve_metadata_space(root, 5);
-        if (err)
-                return err;
+        trans = btrfs_start_transaction(root, 5);
+        if (IS_ERR(trans))
+                return PTR_ERR(trans);
 
-        trans = btrfs_start_transaction(root, 1);
-        if (!trans)
-                goto fail;
         btrfs_set_trans_block_group(trans, dir);
 
-        err = btrfs_find_free_objectid(trans, root, dir->i_ino, &objectid);
-        if (err) {
-                err = -ENOSPC;
-                goto out_unlock;
-        }
-
         inode = btrfs_new_inode(trans, root, dir, dentry->d_name.name,
                                 dentry->d_name.len,
                                 dentry->d_parent->d_inode->i_ino,
@@ -4344,8 +4490,6 @@ static int btrfs_create(struct inode *dir, struct dentry *dentry,
 out_unlock:
         nr = trans->blocks_used;
         btrfs_end_transaction_throttle(trans, root);
-fail:
-        btrfs_unreserve_metadata_space(root, 5);
         if (drop_inode) {
                 inode_dec_link_count(inode);
                 iput(inode);
@@ -4372,21 +4516,21 @@ static int btrfs_link(struct dentry *old_dentry, struct inode *dir,
         if (root->objectid != BTRFS_I(inode)->root->objectid)
                 return -EPERM;
 
-        /*
-         * 1 item for inode ref
-         * 2 items for dir items
-         */
-        err = btrfs_reserve_metadata_space(root, 3);
-        if (err)
-                return err;
-
         btrfs_inc_nlink(inode);
 
         err = btrfs_set_inode_index(dir, &index);
         if (err)
                 goto fail;
 
-        trans = btrfs_start_transaction(root, 1);
+        /*
+         * 1 item for inode ref
+         * 2 items for dir items
+         */
+        trans = btrfs_start_transaction(root, 3);
+        if (IS_ERR(trans)) {
+                err = PTR_ERR(trans);
+                goto fail;
+        }
 
         btrfs_set_trans_block_group(trans, dir);
         atomic_inc(&inode->i_count);
@@ -4405,7 +4549,6 @@ static int btrfs_link(struct dentry *old_dentry, struct inode *dir,
         nr = trans->blocks_used;
         btrfs_end_transaction_throttle(trans, root);
 fail:
-        btrfs_unreserve_metadata_space(root, 3);
         if (drop_inode) {
                 inode_dec_link_count(inode);
                 iput(inode);
@@ -4425,28 +4568,20 @@ static int btrfs_mkdir(struct inode *dir, struct dentry *dentry, int mode)
         u64 index = 0;
         unsigned long nr = 1;
 
+        err = btrfs_find_free_objectid(NULL, root, dir->i_ino, &objectid);
+        if (err)
+                return err;
+
         /*
          * 2 items for inode and ref
          * 2 items for dir items
          * 1 for xattr if selinux is on
          */
-        err = btrfs_reserve_metadata_space(root, 5);
-        if (err)
-                return err;
-
-        trans = btrfs_start_transaction(root, 1);
-        if (!trans) {
-                err = -ENOMEM;
-                goto out_unlock;
-        }
+        trans = btrfs_start_transaction(root, 5);
+        if (IS_ERR(trans))
+                return PTR_ERR(trans);
         btrfs_set_trans_block_group(trans, dir);
 
-        err = btrfs_find_free_objectid(trans, root, dir->i_ino, &objectid);
-        if (err) {
-                err = -ENOSPC;
-                goto out_fail;
-        }
-
         inode = btrfs_new_inode(trans, root, dir, dentry->d_name.name,
                                 dentry->d_name.len,
                                 dentry->d_parent->d_inode->i_ino, objectid,
@@ -4486,9 +4621,6 @@ static int btrfs_mkdir(struct inode *dir, struct dentry *dentry, int mode)
 out_fail:
         nr = trans->blocks_used;
         btrfs_end_transaction_throttle(trans, root);
-
-out_unlock:
-        btrfs_unreserve_metadata_space(root, 5);
         if (drop_on_err)
                 iput(inode);
         btrfs_btree_balance_dirty(root, nr);
@@ -5426,19 +5558,6 @@ static int btrfs_rename(struct inode *old_dir, struct dentry *old_dentry,
         if (S_ISDIR(old_inode->i_mode) && new_inode &&
             new_inode->i_size > BTRFS_EMPTY_DIR_SIZE)
                 return -ENOTEMPTY;
-
-        /*
-         * We want to reserve the absolute worst case amount of items.  So if
-         * both inodes are subvols and we need to unlink them then that would
-         * require 4 item modifications, but if they are both normal inodes it
-         * would require 5 item modifications, so we'll assume their normal
-         * inodes.  So 5 * 2 is 10, plus 1 for the new link, so 11 total items
-         * should cover the worst case number of items we'll modify.
-         */
-        ret = btrfs_reserve_metadata_space(root, 11);
-        if (ret)
-                return ret;
-
         /*
          * we're using rename to replace one file with another.
          * and the replacement file is large.  Start IO on it now so
@@ -5451,8 +5570,18 @@ static int btrfs_rename(struct inode *old_dir, struct dentry *old_dentry,
         /* close the racy window with snapshot create/destroy ioctl */
         if (old_inode->i_ino == BTRFS_FIRST_FREE_OBJECTID)
                 down_read(&root->fs_info->subvol_sem);
+        /*
+         * We want to reserve the absolute worst case amount of items.  So if
+         * both inodes are subvols and we need to unlink them then that would
+         * require 4 item modifications, but if they are both normal inodes it
+         * would require 5 item modifications, so we'll assume their normal
+         * inodes.  So 5 * 2 is 10, plus 1 for the new link, so 11 total items
+         * should cover the worst case number of items we'll modify.
+         */
+        trans = btrfs_start_transaction(root, 20);
+        if (IS_ERR(trans))
+                return PTR_ERR(trans);
 
-        trans = btrfs_start_transaction(root, 1);
         btrfs_set_trans_block_group(trans, new_dir);
 
         if (dest != root)
@@ -5551,7 +5680,6 @@ out_fail:
         if (old_inode->i_ino == BTRFS_FIRST_FREE_OBJECTID)
                 up_read(&root->fs_info->subvol_sem);
 
-        btrfs_unreserve_metadata_space(root, 11);
         return ret;
 }
 
@@ -5658,26 +5786,20 @@ static int btrfs_symlink(struct inode *dir, struct dentry *dentry,
         if (name_len > BTRFS_MAX_INLINE_DATA_SIZE(root))
                 return -ENAMETOOLONG;
 
+        err = btrfs_find_free_objectid(NULL, root, dir->i_ino, &objectid);
+        if (err)
+                return err;
         /*
          * 2 items for inode item and ref
          * 2 items for dir items
          * 1 item for xattr if selinux is on
          */
-        err = btrfs_reserve_metadata_space(root, 5);
-        if (err)
-                return err;
+        trans = btrfs_start_transaction(root, 5);
+        if (IS_ERR(trans))
+                return PTR_ERR(trans);
 
-        trans = btrfs_start_transaction(root, 1);
-        if (!trans)
-                goto out_fail;
         btrfs_set_trans_block_group(trans, dir);
 
-        err = btrfs_find_free_objectid(trans, root, dir->i_ino, &objectid);
-        if (err) {
-                err = -ENOSPC;
-                goto out_unlock;
-        }
-
         inode = btrfs_new_inode(trans, root, dir, dentry->d_name.name,
                                 dentry->d_name.len,
                                 dentry->d_parent->d_inode->i_ino, objectid,
@@ -5749,8 +5871,6 @@ static int btrfs_symlink(struct inode *dir, struct dentry *dentry,
 out_unlock:
         nr = trans->blocks_used;
         btrfs_end_transaction_throttle(trans, root);
-out_fail:
-        btrfs_unreserve_metadata_space(root, 5);
         if (drop_inode) {
                 inode_dec_link_count(inode);
                 iput(inode);
@@ -5771,21 +5891,18 @@ static int prealloc_file_range(struct inode *inode, u64 start, u64 end,
         u64 i_size;
 
         while (num_bytes > 0) {
-                trans = btrfs_start_transaction(root, 1);
+                trans = btrfs_start_transaction(root, 3);
+                if (IS_ERR(trans)) {
+                        ret = PTR_ERR(trans);
+                        break;
+                }
 
                 ret = btrfs_reserve_extent(trans, root, num_bytes,
                                            root->sectorsize, 0, alloc_hint,
                                            (u64)-1, &ins, 1);
                 if (ret) {
-                        WARN_ON(1);
-                        goto stop_trans;
-                }
-
-                ret = btrfs_reserve_metadata_space(root, 3);
-                if (ret) {
-                        btrfs_free_reserved_extent(root, ins.objectid,
-                                                   ins.offset);
-                        goto stop_trans;
+                        btrfs_end_transaction(trans, root);
+                        break;
                 }
 
                 ret = insert_reserved_file_extent(trans, inode,
@@ -5819,14 +5936,8 @@ static int prealloc_file_range(struct inode *inode, u64 start, u64 end,
                 BUG_ON(ret);
 
                 btrfs_end_transaction(trans, root);
-                btrfs_unreserve_metadata_space(root, 3);
         }
         return ret;
-
-stop_trans:
-        btrfs_end_transaction(trans, root);
-        return ret;
-
 }
 
 static long btrfs_fallocate(struct inode *inode, int mode,