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ext4: cache extent hole in extent status tree for ext4_da_map_blocks()

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Currently extent status tree doesn't cache extent hole when a write
looks up in extent tree to make sure whether a block has been allocated
or not.  In this case, we don't put extent hole in extent cache because
later this extent might be removed and a new delayed extent might be
added back.  But it will cause a defect when we do a lot of writes.  If
we don't put extent hole in extent cache, the following writes also need
to access extent tree to look at whether or not a block has been
allocated.  It brings a cache miss.  This commit fixes this defect.
Also if the inode doesn't have any extent, this extent hole will be
cached as well.

Cc: Andreas Dilger <adilger.kernel@dilger.ca>
Signed-off-by: Zheng Liu <wenqing.lz@taobao.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
This commit is contained in:
Zheng Liu 2014-11-25 11:44:37 -05:00 committed by Theodore Ts'o
parent cbd7584e6e
commit 2f8e0a7c6c
4 changed files with 20 additions and 24 deletions
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4
fs/ext4/ext4.h
View File

@ -556,10 +556,8 @@ enum {
#define EXT4_GET_BLOCKS_KEEP_SIZE 0x0080
/* Do not take i_data_sem locking in ext4_map_blocks */
#define EXT4_GET_BLOCKS_NO_LOCK 0x0100
/* Do not put hole in extent cache */
#define EXT4_GET_BLOCKS_NO_PUT_HOLE 0x0200
/* Convert written extents to unwritten */
#define EXT4_GET_BLOCKS_CONVERT_UNWRITTEN 0x0400
#define EXT4_GET_BLOCKS_CONVERT_UNWRITTEN 0x0200
/*
* The bit position of these flags must not overlap with any of the

31
fs/ext4/extents.c
View File

@ -2306,16 +2306,16 @@ ext4_ext_put_gap_in_cache(struct inode *inode, struct ext4_ext_path *path,
ext4_lblk_t block)
{
int depth = ext_depth(inode);
unsigned long len = 0;
ext4_lblk_t lblock = 0;
ext4_lblk_t len;
ext4_lblk_t lblock;
struct ext4_extent *ex;
struct extent_status es;
ex = path[depth].p_ext;
if (ex == NULL) {
/*
* there is no extent yet, so gap is [0;-] and we
* don't cache it
*/
/* there is no extent yet, so gap is [0;-] */
lblock = 0;
len = EXT_MAX_BLOCKS;
ext_debug("cache gap(whole file):");
} else if (block < le32_to_cpu(ex->ee_block)) {
lblock = block;
@ -2324,9 +2324,6 @@ ext4_ext_put_gap_in_cache(struct inode *inode, struct ext4_ext_path *path,
block,
le32_to_cpu(ex->ee_block),
ext4_ext_get_actual_len(ex));
if (!ext4_find_delalloc_range(inode, lblock, lblock + len - 1))
ext4_es_insert_extent(inode, lblock, len, ~0,
EXTENT_STATUS_HOLE);
} else if (block >= le32_to_cpu(ex->ee_block)
+ ext4_ext_get_actual_len(ex)) {
ext4_lblk_t next;
@ -2340,14 +2337,19 @@ ext4_ext_put_gap_in_cache(struct inode *inode, struct ext4_ext_path *path,
block);
BUG_ON(next == lblock);
len = next - lblock;
if (!ext4_find_delalloc_range(inode, lblock, lblock + len - 1))
ext4_es_insert_extent(inode, lblock, len, ~0,
EXTENT_STATUS_HOLE);
} else {
BUG();
}
ext_debug(" -> %u:%lu\n", lblock, len);
ext4_es_find_delayed_extent_range(inode, lblock, lblock + len - 1, &es);
if (es.es_len) {
/* There's delayed extent containing lblock? */
if (es.es_lblk <= lblock)
return;
len = min(es.es_lblk - lblock, len);
}
ext_debug(" -> %u:%u\n", lblock, len);
ext4_es_insert_extent(inode, lblock, len, ~0, EXTENT_STATUS_HOLE);
}
/*
@ -4368,8 +4370,7 @@ int ext4_ext_map_blocks(handle_t *handle, struct inode *inode,
* put just found gap into cache to speed up
* subsequent requests
*/
if ((flags & EXT4_GET_BLOCKS_NO_PUT_HOLE) == 0)
ext4_ext_put_gap_in_cache(inode, path, map->m_lblk);
ext4_ext_put_gap_in_cache(inode, path, map->m_lblk);
goto out2;
}

6
fs/ext4/inode.c
View File

@ -1432,11 +1432,9 @@ static int ext4_da_map_blocks(struct inode *inode, sector_t iblock,
if (ext4_has_inline_data(inode))
retval = 0;
else if (ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS))
retval = ext4_ext_map_blocks(NULL, inode, map,
EXT4_GET_BLOCKS_NO_PUT_HOLE);
retval = ext4_ext_map_blocks(NULL, inode, map, 0);
else
retval = ext4_ind_map_blocks(NULL, inode, map,
EXT4_GET_BLOCKS_NO_PUT_HOLE);
retval = ext4_ind_map_blocks(NULL, inode, map, 0);
add_delayed:
if (retval == 0) {

3
include/trace/events/ext4.h
View File

@ -43,8 +43,7 @@ struct extent_status;
{ EXT4_GET_BLOCKS_METADATA_NOFAIL, "METADATA_NOFAIL" }, \
{ EXT4_GET_BLOCKS_NO_NORMALIZE, "NO_NORMALIZE" }, \
{ EXT4_GET_BLOCKS_KEEP_SIZE, "KEEP_SIZE" }, \
{ EXT4_GET_BLOCKS_NO_LOCK, "NO_LOCK" }, \
{ EXT4_GET_BLOCKS_NO_PUT_HOLE, "NO_PUT_HOLE" })
{ EXT4_GET_BLOCKS_NO_LOCK, "NO_LOCK" })
#define show_mflags(flags) __print_flags(flags, "", \
{ EXT4_MAP_NEW, "N" }, \