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ext4: make xattr inode reads faster

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ext4_xattr_inode_read() currently reads each block sequentially while
waiting for io operation to complete before moving on to the next
block. This prevents request merging in block layer.

Add a ext4_bread_batch() function that starts reads for all blocks
then optionally waits for them to complete. A similar logic is used
in ext4_find_entry(), so update that code to use the new function.

Signed-off-by: Tahsin Erdogan <tahsin@google.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
This commit is contained in:
Tahsin Erdogan
2017-08-06 00:07:01 -04:00
committed by Theodore Ts'o
parent ec00022030
commit 9699d4f91d
4 changed files with 93 additions and 49 deletions
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43
fs/ext4/namei.c
View File

@@ -1342,13 +1342,12 @@ static struct buffer_head * ext4_find_entry (struct inode *dir,
struct super_block *sb;
struct buffer_head *bh_use[NAMEI_RA_SIZE];
struct buffer_head *bh, *ret = NULL;
ext4_lblk_t start, block, b;
ext4_lblk_t start, block;
const u8 *name = d_name->name;
int ra_max = 0; /* Number of bh's in the readahead
size_t ra_max = 0; /* Number of bh's in the readahead
buffer, bh_use[] */
int ra_ptr = 0; /* Current index into readahead
size_t ra_ptr = 0; /* Current index into readahead
buffer */
int num = 0;
ext4_lblk_t nblocks;
int i, namelen, retval;
struct ext4_filename fname;
@@ -1411,31 +1410,17 @@ restart:
if (ra_ptr >= ra_max) {
/* Refill the readahead buffer */
ra_ptr = 0;
b = block;
for (ra_max = 0; ra_max < NAMEI_RA_SIZE; ra_max++) {
/*
* Terminate if we reach the end of the
* directory and must wrap, or if our
* search has finished at this block.
*/
if (b >= nblocks || (num && block == start)) {
bh_use[ra_max] = NULL;
break;
}
num++;
bh = ext4_getblk(NULL, dir, b++, 0);
if (IS_ERR(bh)) {
if (ra_max == 0) {
ret = bh;
goto cleanup_and_exit;
}
break;
}
bh_use[ra_max] = bh;
if (bh)
ll_rw_block(REQ_OP_READ,
REQ_META | REQ_PRIO,
1, &bh);
if (block < start)
ra_max = start - block;
else
ra_max = nblocks - block;
ra_max = min(ra_max, ARRAY_SIZE(bh_use));
retval = ext4_bread_batch(dir, block, ra_max,
false /* wait */, bh_use);
if (retval) {
ret = ERR_PTR(retval);
ra_max = 0;
goto cleanup_and_exit;
}
}
if ((bh = bh_use[ra_ptr++]) == NULL)