ext4: make xattr inode reads faster
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>
diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c
index cc986b8..c1cf020 100644
--- a/fs/ext4/namei.c
+++ b/fs/ext4/namei.c
@@ -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 @@ static struct buffer_head * ext4_find_entry (struct inode *dir,
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)