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Commit c3ce5aa9 authored by Andreas Gruenbacher's avatar Andreas Gruenbacher Committed by Bob Peterson
Browse files

gfs2: Fix metadata read-ahead during truncate 



The metadata read-ahead algorithm broke when switching from recursive to
non-recursive delete: the current algorithm reads ahead blocks at height
N - 1 while deallocating the blocks at hight N.  However, deallocating
the blocks at height N requires a complete walk of the metadata tree,
not only down to height N - 1.  Consequently, all blocks below height
N - 1 will be accessed without read-ahead.

Fix this by issuing read-aheads as early as possible, after each
metapath lookup.

Signed-off-by: default avatarAndreas Gruenbacher <agruenba@redhat.com>
Signed-off-by: default avatarBob Peterson <rpeterso@redhat.com>
parent e8b43fe0

fs/gfs2/bmap.c

+25 −17
Original line number Diff line number Diff line
@@ -279,14 +279,17 @@ static inline __be64 *metapointer(unsigned int height, const struct metapath *mp 
	return p + mp->mp_list[height];

}



static void gfs2_metapath_ra(struct gfs2_glock *gl,

			     const struct buffer_head *bh, const __be64 *pos)

static void gfs2_metapath_ra(struct gfs2_glock *gl, struct metapath *mp,

			     unsigned int height)

{

	struct buffer_head *rabh;

	struct buffer_head *bh = mp->mp_bh[height];

	const __be64 *pos = metapointer(height, mp);

	const __be64 *endp = (const __be64 *)(bh->b_data + bh->b_size);

	const __be64 *t;



	for (t = pos; t < endp; t++) {

		struct buffer_head *rabh;



		if (!*t)

			continue;
@@ -353,12 +356,13 @@ static int lookup_metapath(struct gfs2_inode *ip, struct metapath *mp) 
 *

 * Similar to lookup_metapath, but does lookups for a range of heights

 *

 * Returns: error

 * Returns: error or the number of buffers filled

 */



static int fillup_metapath(struct gfs2_inode *ip, struct metapath *mp, int h)

{

	unsigned int x = 0;

	int ret;



	if (h) {

		/* find the first buffer we need to look up. */
@@ -367,7 +371,10 @@ static int fillup_metapath(struct gfs2_inode *ip, struct metapath *mp, int h) 
				break;

		}

	}

	return __fillup_metapath(ip, mp, x, h);

	ret = __fillup_metapath(ip, mp, x, h);

	if (ret)

		return ret;

	return mp->mp_aheight - x - 1;

}



static inline void release_metapath(struct metapath *mp)
@@ -1309,7 +1316,6 @@ static int trunc_dealloc(struct gfs2_inode *ip, u64 newsize) 
	u32 btotal = 0;

	int ret, state;

	int mp_h; /* metapath buffers are read in to this height */

	sector_t last_ra = 0;

	u64 prev_bnr = 0;

	bool preserve1; /* need to preserve the first meta pointer? */
@@ -1331,6 +1337,11 @@ static int trunc_dealloc(struct gfs2_inode *ip, u64 newsize) 
	ret = lookup_metapath(ip, &mp);

	if (ret)

		goto out_metapath;



	/* issue read-ahead on metadata */

	for (mp_h = 0; mp_h < mp.mp_aheight - 1; mp_h++)

		gfs2_metapath_ra(ip->i_gl, &mp, mp_h);



	if (mp.mp_aheight == ip->i_height)

		state = DEALLOC_MP_FULL; /* We have a complete metapath */

	else
@@ -1352,16 +1363,6 @@ static int trunc_dealloc(struct gfs2_inode *ip, u64 newsize) 
		/* Truncate a full metapath at the given strip height.

		 * Note that strip_h == mp_h in order to be in this state. */

		case DEALLOC_MP_FULL:

			if (mp_h > 0) { /* issue read-ahead on metadata */

				__be64 *top;



				bh = mp.mp_bh[mp_h - 1];

				if (bh->b_blocknr != last_ra) {

					last_ra = bh->b_blocknr;

					top = metaptr1(mp_h - 1, &mp);

					gfs2_metapath_ra(ip->i_gl, bh, top);

				}

			}

			/* If we're truncating to a non-zero size and the mp is

			   at the beginning of file for the strip height, we

			   need to preserve the first metadata pointer. */
@@ -1427,9 +1428,16 @@ static int trunc_dealloc(struct gfs2_inode *ip, u64 newsize) 
		case DEALLOC_FILL_MP:

			/* Fill the buffers out to the current height. */

			ret = fillup_metapath(ip, &mp, mp_h);

			if (ret)

			if (ret < 0)

				goto out;



			/* issue read-ahead on metadata */

			if (mp.mp_aheight > 1) {

				for (; ret > 1; ret--)

					gfs2_metapath_ra(ip->i_gl, &mp,

						mp.mp_aheight - ret);

			}



			/* If buffers found for the entire strip height */

			if (mp.mp_aheight - 1 == strip_h) {

				state = DEALLOC_MP_FULL;