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/xattr.c b/fs/ext4/xattr.c
index 4025666..5fa912e 100644
--- a/fs/ext4/xattr.c
+++ b/fs/ext4/xattr.c
@@ -317,28 +317,41 @@ static void ext4_xattr_inode_set_hash(struct inode *ea_inode, u32 hash)
*/
static int ext4_xattr_inode_read(struct inode *ea_inode, void *buf, size_t size)
{
- unsigned long block = 0;
- struct buffer_head *bh;
- int blocksize = ea_inode->i_sb->s_blocksize;
- size_t csize, copied = 0;
- void *copy_pos = buf;
+ int blocksize = 1 << ea_inode->i_blkbits;
+ int bh_count = (size + blocksize - 1) >> ea_inode->i_blkbits;
+ int tail_size = (size % blocksize) ?: blocksize;
+ struct buffer_head *bhs_inline[8];
+ struct buffer_head **bhs = bhs_inline;
+ int i, ret;
- while (copied < size) {
- csize = (size - copied) > blocksize ? blocksize : size - copied;
- bh = ext4_bread(NULL, ea_inode, block, 0);
- if (IS_ERR(bh))
- return PTR_ERR(bh);
- if (!bh)
- return -EFSCORRUPTED;
-
- memcpy(copy_pos, bh->b_data, csize);
- brelse(bh);
-
- copy_pos += csize;
- block += 1;
- copied += csize;
+ if (bh_count > ARRAY_SIZE(bhs_inline)) {
+ bhs = kmalloc_array(bh_count, sizeof(*bhs), GFP_NOFS);
+ if (!bhs)
+ return -ENOMEM;
}
- return 0;
+
+ ret = ext4_bread_batch(ea_inode, 0 /* block */, bh_count,
+ true /* wait */, bhs);
+ if (ret)
+ goto free_bhs;
+
+ for (i = 0; i < bh_count; i++) {
+ /* There shouldn't be any holes in ea_inode. */
+ if (!bhs[i]) {
+ ret = -EFSCORRUPTED;
+ goto put_bhs;
+ }
+ memcpy((char *)buf + blocksize * i, bhs[i]->b_data,
+ i < bh_count - 1 ? blocksize : tail_size);
+ }
+ ret = 0;
+put_bhs:
+ for (i = 0; i < bh_count; i++)
+ brelse(bhs[i]);
+free_bhs:
+ if (bhs != bhs_inline)
+ kfree(bhs);
+ return ret;
}
static int ext4_xattr_inode_iget(struct inode *parent, unsigned long ea_ino,