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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: Andreas Gruenbacher <agruenba@redhat.com>
Signed-off-by: Bob Peterson <rpeterso@redhat.com>
This commit is contained in:
Andreas Gruenbacher 2017-12-08 21:11:39 +01:00 committed by Bob Peterson
parent e8b43fe0c1
commit c3ce5aa9b0
1 changed files with 25 additions and 17 deletions
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42
fs/gfs2/bmap.c
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@ -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;