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kernel/0013-ext4-race-condition-protection-for-ext4_convert_unwr.patch

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From 5ff6b4cc64765e10df509a60e902561efdeb58d5 Mon Sep 17 00:00:00 2001
From: Dmitry Monakhov <dmonakhov@openvz.org>
Date: Fri, 5 Oct 2012 11:32:04 -0400
Subject: [PATCH 13/13] ext4: race-condition protection for
ext4_convert_unwritten_extents_endio
We assumed that at the time we call ext4_convert_unwritten_extents_endio()
extent in question is fully inside [map.m_lblk, map->m_len] because
it was already split during submission. But this may not be true due to
a race between writeback vs fallocate.
If extent in question is larger than requested we will split it again.
Special precautions should being done if zeroout required because
[map.m_lblk, map->m_len] already contains valid data.
Signed-off-by: Dmitry Monakhov <dmonakhov@openvz.org>
(cherry picked from commit 0d4b4ff5282d07a4f83b87b3117cd898b0a3f673)
---
fs/ext4/extents.c | 57 ++++++++++++++++++++++++++++++++++++++++++++-----------
1 file changed, 46 insertions(+), 11 deletions(-)
diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index ea2db86..ee0d61c 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -52,6 +52,9 @@
#define EXT4_EXT_MARK_UNINIT1 0x2 /* mark first half uninitialized */
#define EXT4_EXT_MARK_UNINIT2 0x4 /* mark second half uninitialized */
+#define EXT4_EXT_DATA_VALID1 0x8 /* first half contains valid data */
+#define EXT4_EXT_DATA_VALID2 0x10 /* second half contains valid data */
+
static __le32 ext4_extent_block_csum(struct inode *inode,
struct ext4_extent_header *eh)
{
@@ -2897,6 +2900,9 @@ static int ext4_split_extent_at(handle_t *handle,
unsigned int ee_len, depth;
int err = 0;
+ BUG_ON((split_flag & (EXT4_EXT_DATA_VALID1 | EXT4_EXT_DATA_VALID2)) ==
+ (EXT4_EXT_DATA_VALID1 | EXT4_EXT_DATA_VALID2));
+
ext_debug("ext4_split_extents_at: inode %lu, logical"
"block %llu\n", inode->i_ino, (unsigned long long)split);
@@ -2955,7 +2961,14 @@ static int ext4_split_extent_at(handle_t *handle,
err = ext4_ext_insert_extent(handle, inode, path, &newex, flags);
if (err == -ENOSPC && (EXT4_EXT_MAY_ZEROOUT & split_flag)) {
- err = ext4_ext_zeroout(inode, &orig_ex);
+ if (split_flag & (EXT4_EXT_DATA_VALID1|EXT4_EXT_DATA_VALID2)) {
+ if (split_flag & EXT4_EXT_DATA_VALID1)
+ err = ext4_ext_zeroout(inode, ex2);
+ else
+ err = ext4_ext_zeroout(inode, ex);
+ } else
+ err = ext4_ext_zeroout(inode, &orig_ex);
+
if (err)
goto fix_extent_len;
/* update the extent length and mark as initialized */
@@ -3008,12 +3021,13 @@ static int ext4_split_extent(handle_t *handle,
uninitialized = ext4_ext_is_uninitialized(ex);
if (map->m_lblk + map->m_len < ee_block + ee_len) {
- split_flag1 = split_flag & EXT4_EXT_MAY_ZEROOUT ?
- EXT4_EXT_MAY_ZEROOUT : 0;
+ split_flag1 = split_flag & EXT4_EXT_MAY_ZEROOUT;
flags1 = flags | EXT4_GET_BLOCKS_PRE_IO;
if (uninitialized)
split_flag1 |= EXT4_EXT_MARK_UNINIT1 |
EXT4_EXT_MARK_UNINIT2;
+ if (split_flag & EXT4_EXT_DATA_VALID2)
+ split_flag1 |= EXT4_EXT_DATA_VALID1;
err = ext4_split_extent_at(handle, inode, path,
map->m_lblk + map->m_len, split_flag1, flags1);
if (err)
@@ -3026,8 +3040,8 @@ static int ext4_split_extent(handle_t *handle,
return PTR_ERR(path);
if (map->m_lblk >= ee_block) {
- split_flag1 = split_flag & EXT4_EXT_MAY_ZEROOUT ?
- EXT4_EXT_MAY_ZEROOUT : 0;
+ split_flag1 = split_flag & (EXT4_EXT_MAY_ZEROOUT |
+ EXT4_EXT_DATA_VALID2);
if (uninitialized)
split_flag1 |= EXT4_EXT_MARK_UNINIT1;
if (split_flag & EXT4_EXT_MARK_UNINIT2)
@@ -3305,26 +3319,47 @@ static int ext4_split_unwritten_extents(handle_t *handle,
split_flag |= ee_block + ee_len <= eof_block ? EXT4_EXT_MAY_ZEROOUT : 0;
split_flag |= EXT4_EXT_MARK_UNINIT2;
-
+ if (flags & EXT4_GET_BLOCKS_CONVERT)
+ split_flag |= EXT4_EXT_DATA_VALID2;
flags |= EXT4_GET_BLOCKS_PRE_IO;
return ext4_split_extent(handle, inode, path, map, split_flag, flags);
}
static int ext4_convert_unwritten_extents_endio(handle_t *handle,
- struct inode *inode,
- struct ext4_ext_path *path)
+ struct inode *inode,
+ struct ext4_map_blocks *map,
+ struct ext4_ext_path *path)
{
struct ext4_extent *ex;
+ ext4_lblk_t ee_block;
+ unsigned int ee_len;
int depth;
int err = 0;
depth = ext_depth(inode);
ex = path[depth].p_ext;
+ ee_block = le32_to_cpu(ex->ee_block);
+ ee_len = ext4_ext_get_actual_len(ex);
ext_debug("ext4_convert_unwritten_extents_endio: inode %lu, logical"
"block %llu, max_blocks %u\n", inode->i_ino,
- (unsigned long long)le32_to_cpu(ex->ee_block),
- ext4_ext_get_actual_len(ex));
+ (unsigned long long)ee_block, ee_len);
+
+ /* If extent is larger than requested then split is required */
+ if (ee_block != map->m_lblk || ee_len > map->m_len) {
+ err = ext4_split_unwritten_extents(handle, inode, map, path,
+ EXT4_GET_BLOCKS_CONVERT);
+ if (err < 0)
+ goto out;
+ ext4_ext_drop_refs(path);
+ path = ext4_ext_find_extent(inode, map->m_lblk, path);
+ if (IS_ERR(path)) {
+ err = PTR_ERR(path);
+ goto out;
+ }
+ depth = ext_depth(inode);
+ ex = path[depth].p_ext;
+ }
err = ext4_ext_get_access(handle, inode, path + depth);
if (err)
@@ -3634,7 +3669,7 @@ ext4_ext_handle_uninitialized_extents(handle_t *handle, struct inode *inode,
}
/* IO end_io complete, convert the filled extent to written */
if ((flags & EXT4_GET_BLOCKS_CONVERT)) {
- ret = ext4_convert_unwritten_extents_endio(handle, inode,
+ ret = ext4_convert_unwritten_extents_endio(handle, inode, map,
path);
if (ret >= 0) {
ext4_update_inode_fsync_trans(handle, inode, 1);
--
1.7.12.rc0.22.gcdd159b
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