Commit dfe4d34b authored by Bob Peterson's avatar Bob Peterson Committed by Steven Whitehouse
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GFS2: Add readahead to sequential directory traversal 



This patch adds read-ahead capability to GFS2's
directory hash table management.  It greatly improves
performance for some directory operations.  For example:
In one of my file systems that has 1000 directories, each
of which has 1000 files, time to execute a recursive
ls (time ls -fR /mnt/gfs2 > /dev/null) was reduced
from 2m2.814s on a stock kernel to 0m45.938s.

Signed-off-by: default avatarBob Peterson <rpeterso@redhat.com>
Signed-off-by: default avatarSteven Whitehouse <swhiteho@redhat.com>
parent 20ed0535

fs/gfs2/dir.c

+53 −3
Original line number Diff line number Diff line
@@ -76,6 +76,8 @@ 
#define IS_LEAF     1 /* Hashed (leaf) directory */

#define IS_DINODE   2 /* Linear (stuffed dinode block) directory */



#define MAX_RA_BLOCKS 32 /* max read-ahead blocks */



#define gfs2_disk_hash2offset(h) (((u64)(h)) >> 1)

#define gfs2_dir_offset2hash(p) ((u32)(((u64)(p)) << 1))
@@ -1376,6 +1378,50 @@ out: 
	return error;

}



/* gfs2_dir_readahead - Issue read-ahead requests for leaf blocks.

 *

 * Note: we can't calculate each index like dir_e_read can because we don't

 * have the leaf, and therefore we don't have the depth, and therefore we

 * don't have the length. So we have to just read enough ahead to make up

 * for the loss of information. */

static void gfs2_dir_readahead(struct inode *inode, unsigned hsize, u32 index,

			       struct file_ra_state *f_ra)

{

	struct gfs2_inode *ip = GFS2_I(inode);

	struct gfs2_glock *gl = ip->i_gl;

	struct buffer_head *bh;

	u64 blocknr = 0, last;

	unsigned count;



	/* First check if we've already read-ahead for the whole range. */

	if (!f_ra || index + MAX_RA_BLOCKS < f_ra->start)

		return;



	f_ra->start = max((pgoff_t)index, f_ra->start);

	for (count = 0; count < MAX_RA_BLOCKS; count++) {

		if (f_ra->start >= hsize) /* if exceeded the hash table */

			break;



		last = blocknr;

		blocknr = be64_to_cpu(ip->i_hash_cache[f_ra->start]);

		f_ra->start++;

		if (blocknr == last)

			continue;



		bh = gfs2_getbuf(gl, blocknr, 1);

		if (trylock_buffer(bh)) {

			if (buffer_uptodate(bh)) {

				unlock_buffer(bh);

				brelse(bh);

				continue;

			}

			bh->b_end_io = end_buffer_read_sync;

			submit_bh(READA | REQ_META, bh);

			continue;

		}

		brelse(bh);

	}

}



/**

 * dir_e_read - Reads the entries from a directory into a filldir buffer
@@ -1388,7 +1434,7 @@ out: 
 */



static int dir_e_read(struct inode *inode, u64 *offset, void *opaque,

		      filldir_t filldir)

		      filldir_t filldir, struct file_ra_state *f_ra)

{

	struct gfs2_inode *dip = GFS2_I(inode);

	u32 hsize, len = 0;
@@ -1402,10 +1448,14 @@ static int dir_e_read(struct inode *inode, u64 *offset, void *opaque, 
	hash = gfs2_dir_offset2hash(*offset);

	index = hash >> (32 - dip->i_depth);



	if (f_ra && dip->i_hash_cache == NULL)

		f_ra->start = 0;

	lp = gfs2_dir_get_hash_table(dip);

	if (IS_ERR(lp))

		return PTR_ERR(lp);



	gfs2_dir_readahead(inode, hsize, index, f_ra);



	while (index < hsize) {

		error = gfs2_dir_read_leaf(inode, offset, opaque, filldir,

					   &copied, &depth,
@@ -1423,7 +1473,7 @@ static int dir_e_read(struct inode *inode, u64 *offset, void *opaque, 
}



int gfs2_dir_read(struct inode *inode, u64 *offset, void *opaque,

		  filldir_t filldir)

		  filldir_t filldir, struct file_ra_state *f_ra)

{

	struct gfs2_inode *dip = GFS2_I(inode);

	struct gfs2_sbd *sdp = GFS2_SB(inode);
@@ -1437,7 +1487,7 @@ int gfs2_dir_read(struct inode *inode, u64 *offset, void *opaque, 
		return 0;



	if (dip->i_diskflags & GFS2_DIF_EXHASH)

		return dir_e_read(inode, offset, opaque, filldir);

		return dir_e_read(inode, offset, opaque, filldir, f_ra);



	if (!gfs2_is_stuffed(dip)) {

		gfs2_consist_inode(dip);

fs/gfs2/dir.h

+1 −1
Original line number Diff line number Diff line
@@ -25,7 +25,7 @@ extern int gfs2_dir_add(struct inode *inode, const struct qstr *filename, 
			const struct gfs2_inode *ip);

extern int gfs2_dir_del(struct gfs2_inode *dip, const struct dentry *dentry);

extern int gfs2_dir_read(struct inode *inode, u64 *offset, void *opaque,

			 filldir_t filldir);

			 filldir_t filldir, struct file_ra_state *f_ra);

extern int gfs2_dir_mvino(struct gfs2_inode *dip, const struct qstr *filename,

			  const struct gfs2_inode *nip, unsigned int new_type);

fs/gfs2/export.c

+2 −1
Original line number Diff line number Diff line
@@ -99,6 +99,7 @@ static int gfs2_get_name(struct dentry *parent, char *name, 
	struct gfs2_holder gh;

	u64 offset = 0;

	int error;

	struct file_ra_state f_ra = { .start = 0 };



	if (!dir)

		return -EINVAL;
@@ -118,7 +119,7 @@ static int gfs2_get_name(struct dentry *parent, char *name, 
	if (error)

		return error;



	error = gfs2_dir_read(dir, &offset, &gnfd, get_name_filldir);

	error = gfs2_dir_read(dir, &offset, &gnfd, get_name_filldir, &f_ra);



	gfs2_glock_dq_uninit(&gh);

fs/gfs2/file.c

+1 −1
Original line number Diff line number Diff line
@@ -105,7 +105,7 @@ static int gfs2_readdir(struct file *file, void *dirent, filldir_t filldir) 
		return error;

	}



	error = gfs2_dir_read(dir, &offset, dirent, filldir);

	error = gfs2_dir_read(dir, &offset, dirent, filldir, &file->f_ra);



	gfs2_glock_dq_uninit(&d_gh);

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