[PATCH -v2] btrfs: Use correct values when updating inode i_size on fallocate

["Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>]

Even though we allocate more, we should be updating inode i_size
as per the arguments passed

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
---
Changes from V1:
 We should update i_size only if actual_len and cur_offset are both
 larger than i_size. Otherwise if actual_len is < i_size and cur_offset > i_size
 we may end up setting wrong i_size value

 fs/btrfs/inode.c |   17 ++++++++++++-----
 1 files changed, 12 insertions(+), 5 deletions(-)

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 5440bab..ac4cb6b 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -5789,7 +5789,7 @@ out_fail:
 }
 
 static int prealloc_file_range(struct inode *inode, u64 start, u64 end,
-			       u64 alloc_hint, int mode)
+			u64 alloc_hint, int mode, loff_t actual_len)
 {
 	struct btrfs_trans_handle *trans;
 	struct btrfs_root *root = BTRFS_I(inode)->root;
@@ -5798,6 +5798,7 @@ static int prealloc_file_range(struct inode *inode, u64 start, u64 end,
 	u64 cur_offset = start;
 	u64 num_bytes = end - start;
 	int ret = 0;
+	u64 i_size;
 
 	while (num_bytes > 0) {
 		alloc_size = min(num_bytes, root->fs_info->max_extent);
@@ -5835,9 +5836,15 @@ static int prealloc_file_range(struct inode *inode, u64 start, u64 end,
 		inode->i_ctime = CURRENT_TIME;
 		BTRFS_I(inode)->flags |= BTRFS_INODE_PREALLOC;
 		if (!(mode & FALLOC_FL_KEEP_SIZE) &&
-		    cur_offset > inode->i_size) {
-			i_size_write(inode, cur_offset);
-			btrfs_ordered_update_i_size(inode, cur_offset, NULL);
+			(actual_len > inode->i_size) &&
+			(cur_offset > inode->i_size)) {
+
+			if (cur_offset > actual_len)
+				i_size  = actual_len;
+			else
+				i_size = cur_offset;
+			i_size_write(inode, i_size);
+			btrfs_ordered_update_i_size(inode, i_size, NULL);
 		}
 
 		ret = btrfs_update_inode(trans, root, inode);
@@ -5930,7 +5937,7 @@ static long btrfs_fallocate(struct inode *inode, int mode,
 		     !test_bit(EXTENT_FLAG_PREALLOC, &em->flags))) {
 			ret = prealloc_file_range(inode,
 						  cur_offset, last_byte,
-						  alloc_hint, mode);
+						alloc_hint, mode, offset+len);
 			if (ret < 0) {
 				free_extent_map(em);
 				break;
-- 
1.6.6.1.383.g5a9f