| From 9ae57b4a344fc808a2b7b763ab86a4a4a0a82410 Mon Sep 17 00:00:00 2001 |
| From: Mingming <cmm@us.ibm.com> |
| Date: Fri, 6 Nov 2009 04:01:23 -0500 |
| Subject: [PATCH 56/85] ext4: Fix return value of ext4_split_unwritten_extents() to fix direct I/O |
| |
| (cherry picked from commit ba230c3f6dc88ec008806adb27b12088486d508e) |
| |
| To prepare for a direct I/O write, we need to split the unwritten |
| extents before submitting the I/O. When no extents needed to be |
| split, ext4_split_unwritten_extents() was incorrectly returning 0 |
| instead of the size of uninitialized extents. This bug caused the |
| wrong return value sent back to VFS code when it gets called from |
| async IO path, leading to an unnecessary fall back to buffered IO. |
| |
| This bug also hid the fact that the check to see whether or not a |
| split would be necessary was incorrect; we can only skip splitting the |
| extent if the write completely covers the uninitialized extent. |
| |
| Signed-off-by: Mingming Cao <cmm@us.ibm.com> |
| Signed-off-by: "Theodore Ts'o" <tytso@mit.edu> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de> |
| --- |
| fs/ext4/extents.c | 13 +++++++------ |
| 1 file changed, 7 insertions(+), 6 deletions(-) |
| |
| --- a/fs/ext4/extents.c |
| +++ b/fs/ext4/extents.c |
| @@ -2784,6 +2784,8 @@ fix_extent_len: |
| * into three uninitialized extent(at most). After IO complete, the part |
| * being filled will be convert to initialized by the end_io callback function |
| * via ext4_convert_unwritten_extents(). |
| + * |
| + * Returns the size of uninitialized extent to be written on success. |
| */ |
| static int ext4_split_unwritten_extents(handle_t *handle, |
| struct inode *inode, |
| @@ -2801,7 +2803,6 @@ static int ext4_split_unwritten_extents( |
| unsigned int allocated, ee_len, depth; |
| ext4_fsblk_t newblock; |
| int err = 0; |
| - int ret = 0; |
| |
| ext_debug("ext4_split_unwritten_extents: inode %lu," |
| "iblock %llu, max_blocks %u\n", inode->i_ino, |
| @@ -2819,12 +2820,12 @@ static int ext4_split_unwritten_extents( |
| ext4_ext_store_pblock(&orig_ex, ext_pblock(ex)); |
| |
| /* |
| - * if the entire unintialized extent length less than |
| - * the size of extent to write, there is no need to split |
| - * uninitialized extent |
| + * If the uninitialized extent begins at the same logical |
| + * block where the write begins, and the write completely |
| + * covers the extent, then we don't need to split it. |
| */ |
| - if (allocated <= max_blocks) |
| - return ret; |
| + if ((iblock == ee_block) && (allocated <= max_blocks)) |
| + return allocated; |
| |
| err = ext4_ext_get_access(handle, inode, path + depth); |
| if (err) |
