Btrfs: Make fallocate(2) more ENOSPC friendly

fallocate(2) may allocate large number of file extents, so it's not
good to do it in a single transaction. This patch make fallocate(2)
start a new transaction for each file extents it allocates.

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

1 files changed, 32 insertions, 33 deletions

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index eb2db3bde236..8d8baaa61504 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -5664,10 +5664,10 @@ out_fail:
         return err;
 }
 
-static int prealloc_file_range(struct btrfs_trans_handle *trans,
-                               struct inode *inode, u64 start, u64 end,
+static int prealloc_file_range(struct inode *inode, u64 start, u64 end,
                                u64 alloc_hint, int mode)
 {
+        struct btrfs_trans_handle *trans;
         struct btrfs_root *root = BTRFS_I(inode)->root;
         struct btrfs_key ins;
         u64 alloc_size;
@@ -5678,17 +5678,23 @@ static int prealloc_file_range(struct btrfs_trans_handle *trans,
         while (num_bytes > 0) {
                 alloc_size = min(num_bytes, root->fs_info->max_extent);
 
-                ret = btrfs_reserve_metadata_space(root, 1);
-                if (ret)
-                        goto out;
-
                 ret = btrfs_reserve_extent(trans, root, alloc_size,
                                            root->sectorsize, 0, alloc_hint,
                                            (u64)-1, &ins, 1);
                 if (ret) {
                         WARN_ON(1);
-                        goto out;
+                        break;
+                }
+
+                ret = btrfs_reserve_metadata_space(root, 3);
+                if (ret) {
+                        btrfs_free_reserved_extent(root, ins.objectid,
+                                                   ins.offset);
+                        break;
                 }
+
+                trans = btrfs_start_transaction(root, 1);
+
                 ret = insert_reserved_file_extent(trans, inode,
                                                   cur_offset, ins.objectid,
                                                   ins.offset, ins.offset,
@@ -5697,22 +5703,25 @@ static int prealloc_file_range(struct btrfs_trans_handle *trans,
                 BUG_ON(ret);
                 btrfs_drop_extent_cache(inode, cur_offset,
                                         cur_offset + ins.offset -1, 0);
+
                 num_bytes -= ins.offset;
                 cur_offset += ins.offset;
                 alloc_hint = ins.objectid + ins.offset;
-                btrfs_unreserve_metadata_space(root, 1);
-        }
-out:
-        if (cur_offset > start) {
+
                 inode->i_ctime = CURRENT_TIME;
                 BTRFS_I(inode)->flags |= BTRFS_INODE_PREALLOC;
                 if (!(mode & FALLOC_FL_KEEP_SIZE) &&
-                    cur_offset > i_size_read(inode))
-                        btrfs_i_size_write(inode, cur_offset);
+                    cur_offset > inode->i_size) {
+                        i_size_write(inode, cur_offset);
+                        btrfs_ordered_update_i_size(inode, cur_offset, NULL);
+                }
+
                 ret = btrfs_update_inode(trans, root, inode);
                 BUG_ON(ret);
-        }
 
+                btrfs_end_transaction(trans, root);
+                btrfs_unreserve_metadata_space(root, 3);
+        }
         return ret;
 }
 
@@ -5727,8 +5736,6 @@ static long btrfs_fallocate(struct inode *inode, int mode,
         u64 locked_end;
         u64 mask = BTRFS_I(inode)->root->sectorsize - 1;
         struct extent_map *em;
-        struct btrfs_trans_handle *trans;
-        struct btrfs_root *root;
         int ret;
 
         alloc_start = offset & ~mask;
@@ -5747,9 +5754,7 @@ static long btrfs_fallocate(struct inode *inode, int mode,
                         goto out;
         }
 
-        root = BTRFS_I(inode)->root;
-
-        ret = btrfs_check_data_free_space(root, inode,
+        ret = btrfs_check_data_free_space(BTRFS_I(inode)->root, inode,
                                           alloc_end - alloc_start);
         if (ret)
                 goto out;
@@ -5758,12 +5763,6 @@ static long btrfs_fallocate(struct inode *inode, int mode,
         while (1) {
                 struct btrfs_ordered_extent *ordered;
 
-                trans = btrfs_start_transaction(BTRFS_I(inode)->root, 1);
-                if (!trans) {
-                        ret = -EIO;
-                        goto out_free;
-                }
-
                 /* the extent lock is ordered inside the running
                  * transaction
                  */
@@ -5777,8 +5776,6 @@ static long btrfs_fallocate(struct inode *inode, int mode,
                         btrfs_put_ordered_extent(ordered);
                         unlock_extent(&BTRFS_I(inode)->io_tree,
                                       alloc_start, locked_end, GFP_NOFS);
-                        btrfs_end_transaction(trans, BTRFS_I(inode)->root);
-
                         /*
                          * we can't wait on the range with the transaction
                          * running or with the extent lock held
@@ -5799,9 +5796,12 @@ static long btrfs_fallocate(struct inode *inode, int mode,
                 BUG_ON(IS_ERR(em) || !em);
                 last_byte = min(extent_map_end(em), alloc_end);
                 last_byte = (last_byte + mask) & ~mask;
-                if (em->block_start == EXTENT_MAP_HOLE) {
-                        ret = prealloc_file_range(trans, inode, cur_offset,
-                                                last_byte, alloc_hint, mode);
+                if (em->block_start == EXTENT_MAP_HOLE ||
+                    (cur_offset >= inode->i_size &&
+                     !test_bit(EXTENT_FLAG_PREALLOC, &em->flags))) {
+                        ret = prealloc_file_range(inode,
+                                                  cur_offset, last_byte,
+                                                  alloc_hint, mode);
                         if (ret < 0) {
                                 free_extent_map(em);
                                 break;
@@ -5820,9 +5820,8 @@ static long btrfs_fallocate(struct inode *inode, int mode,
         unlock_extent(&BTRFS_I(inode)->io_tree, alloc_start, locked_end,
                       GFP_NOFS);
 
-        btrfs_end_transaction(trans, BTRFS_I(inode)->root);
-out_free:
-        btrfs_free_reserved_data_space(root, inode, alloc_end - alloc_start);
+        btrfs_free_reserved_data_space(BTRFS_I(inode)->root, inode,
+                                       alloc_end - alloc_start);
 out:
         mutex_unlock(&inode->i_mutex);
         return ret;