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Date: Fri, 18 Jan 2013 13:00:38 +0100
From: Jan Kara <jack@...e.cz>
To: Ted Tso <tytso@....edu>
Cc: linux-ext4@...r.kernel.org, Jan Kara <jack@...e.cz>
Subject: [PATCH 04/12] ext4: Disable merging of uninitialized extents
Merging of uninitialized extents creates all sorts of interesting race
possibilities when writeback / DIO races with fallocate. Thus
ext4_convert_unwritten_extents_endio() has to deal with a case where
extent to be converted needs to be split out first. That isn't nice
for two reasons:
1) It may need allocation of extent tree block so ENOSPC is possible.
2) It complicates end_io handling code
So we disable merging of uninitialized extents which allows us to simplify
the code. Extents will get merged after they are converted to initialized
ones.
Reviewed-by: Zheng Liu <wenqing.lz@...bao.com>
Signed-off-by: Jan Kara <jack@...e.cz>
---
fs/ext4/extents.c | 61 +++++++++++++++-------------------------------------
1 files changed, 18 insertions(+), 43 deletions(-)
diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index 26af228..f1ce33a 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -54,9 +54,6 @@
#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)
{
@@ -1579,20 +1576,17 @@ int
ext4_can_extents_be_merged(struct inode *inode, struct ext4_extent *ex1,
struct ext4_extent *ex2)
{
- unsigned short ext1_ee_len, ext2_ee_len, max_len;
+ unsigned ext1_ee_len, ext2_ee_len;
/*
- * Make sure that either both extents are uninitialized, or
- * both are _not_.
+ * Make sure that both extents are initialized. We don't merge
+ * uninitialized extents so that we can be sure that end_io code has
+ * the extent that was written properly split out and conversion to
+ * initialized is trivial.
*/
- if (ext4_ext_is_uninitialized(ex1) ^ ext4_ext_is_uninitialized(ex2))
+ if (ext4_ext_is_uninitialized(ex1) || ext4_ext_is_uninitialized(ex2))
return 0;
- if (ext4_ext_is_uninitialized(ex1))
- max_len = EXT_UNINIT_MAX_LEN;
- else
- max_len = EXT_INIT_MAX_LEN;
-
ext1_ee_len = ext4_ext_get_actual_len(ex1);
ext2_ee_len = ext4_ext_get_actual_len(ex2);
@@ -1605,7 +1599,7 @@ ext4_can_extents_be_merged(struct inode *inode, struct ext4_extent *ex1,
* as an RO_COMPAT feature, refuse to merge to extents if
* this can result in the top bit of ee_len being set.
*/
- if (ext1_ee_len + ext2_ee_len > max_len)
+ if (ext1_ee_len + ext2_ee_len > EXT_INIT_MAX_LEN)
return 0;
#ifdef AGGRESSIVE_TEST
if (ext1_ee_len >= 4)
@@ -2959,9 +2953,6 @@ 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);
@@ -3020,14 +3011,7 @@ 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)) {
- 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);
-
+ err = ext4_ext_zeroout(inode, &orig_ex);
if (err)
goto fix_extent_len;
/* update the extent length and mark as initialized */
@@ -3085,8 +3069,6 @@ static int ext4_split_extent(handle_t *handle,
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)
@@ -3099,8 +3081,7 @@ 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_DATA_VALID2);
+ split_flag1 = split_flag & EXT4_EXT_MAY_ZEROOUT;
if (uninitialized)
split_flag1 |= EXT4_EXT_MARK_UNINIT1;
if (split_flag & EXT4_EXT_MARK_UNINIT2)
@@ -3379,8 +3360,7 @@ 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);
}
@@ -3405,20 +3385,15 @@ static int ext4_convert_unwritten_extents_endio(handle_t *handle,
"block %llu, max_blocks %u\n", inode->i_ino,
(unsigned long long)ee_block, ee_len);
- /* If extent is larger than requested then split is required */
+ /* Extent is larger than requested? */
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;
+ EXT4_ERROR_INODE(inode, "Written extent modified before IO"
+ " finished: extent logical block %llu, len %u; IO"
+ " logical block %llu, len %u\n",
+ (unsigned long long)ee_block, ee_len,
+ (unsigned long long)map->m_lblk, map->m_len);
+ err = -EIO;
+ goto out;
}
err = ext4_ext_get_access(handle, inode, path + depth);
--
1.7.1
--
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