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Commit dc7868fc authored by Fengguang Wu's avatar Fengguang Wu Committed by Linus Torvalds
Browse files

readahead: convert ext3/ext4 invocations 



Convert ext3/ext4 dir reads to use on-demand readahead.

Readahead for dirs operates _not_ on file level, but on blockdev level.  This
makes a difference when the data blocks are not continuous.  And the read
routine is somehow opaque: there's no handy info about the status of current
page.  So a simplified call scheme is employed: to call into readahead
whenever the current page falls out of readahead windows.

Signed-off-by: default avatarFengguang Wu <wfg@mail.ustc.edu.cn>
Cc: Steven Pratt <slpratt@austin.ibm.com>
Cc: Ram Pai <linuxram@us.ibm.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent a08a166f

fs/ext3/dir.c

+8 −6
Original line number Diff line number Diff line
@@ -136,12 +136,14 @@ static int ext3_readdir(struct file * filp, 
		err = ext3_get_blocks_handle(NULL, inode, blk, 1,

						&map_bh, 0, 0);

		if (err > 0) {

			page_cache_readahead(sb->s_bdev->bd_inode->i_mapping,

				&filp->f_ra,

				filp,

				map_bh.b_blocknr >>

					(PAGE_CACHE_SHIFT - inode->i_blkbits),

				1);

			pgoff_t index = map_bh.b_blocknr >>

					(PAGE_CACHE_SHIFT - inode->i_blkbits);

			if (!ra_has_index(&filp->f_ra, index))

				page_cache_readahead_ondemand(

					sb->s_bdev->bd_inode->i_mapping,

					&filp->f_ra, filp,

					NULL, index, 1);

			filp->f_ra.prev_index = index;

			bh = ext3_bread(NULL, inode, blk, 0, &err);

		}

fs/ext4/dir.c

+8 −6
Original line number Diff line number Diff line
@@ -135,12 +135,14 @@ static int ext4_readdir(struct file * filp, 
		map_bh.b_state = 0;

		err = ext4_get_blocks_wrap(NULL, inode, blk, 1, &map_bh, 0, 0);

		if (err > 0) {

			page_cache_readahead(sb->s_bdev->bd_inode->i_mapping,

				&filp->f_ra,

				filp,

				map_bh.b_blocknr >>

					(PAGE_CACHE_SHIFT - inode->i_blkbits),

				1);

			pgoff_t index = map_bh.b_blocknr >>

					(PAGE_CACHE_SHIFT - inode->i_blkbits);

			if (!ra_has_index(&filp->f_ra, index))

				page_cache_readahead_ondemand(

					sb->s_bdev->bd_inode->i_mapping,

					&filp->f_ra, filp,

					NULL, index, 1);

			filp->f_ra.prev_index = index;

			bh = ext4_bread(NULL, inode, blk, 0, &err);

		}