The fix from commit 2d29f6b96d8f introduced an unexpected performance
regression when allocating blocks. Fix by rewriting the overly
complicated wrap-around logic in gfs2_rbm_find in a more reasonable way.
Discovered and verified with iozone.
Fixes: 2d29f6b96d8f ("gfs2: Fix loop in gfs2_rbm_find")
Cc: stable@xxxxxxxxxxxxxxx # v3.13+
Signed-off-by: Andreas Gruenbacher <agruenba@xxxxxxxxxx>
---
fs/gfs2/rgrp.c | 40 +++++++++++++---------------------------
1 file changed, 13 insertions(+), 27 deletions(-)
diff --git a/fs/gfs2/rgrp.c b/fs/gfs2/rgrp.c
index 831d7cb5a49c4..3f16411d885d9 100644
--- a/fs/gfs2/rgrp.c
+++ b/fs/gfs2/rgrp.c
@@ -1730,25 +1730,15 @@ static int gfs2_rbm_find(struct gfs2_rbm *rbm, u8 state, u32 *minext,
const struct gfs2_inode *ip, bool nowrap)
{
struct buffer_head *bh;
- int initial_bii;
- u32 initial_offset;
int first_bii = rbm->bii;
u32 first_offset = rbm->offset;
u32 offset;
u8 *buffer;
- int n = 0;
- int iters = rbm->rgd->rd_length;
+ bool wrapped = false;
int ret;
struct gfs2_bitmap *bi;
struct gfs2_extent maxext = { .rbm.rgd = rbm->rgd, };
- /* If we are not starting at the beginning of a bitmap, then we
- * need to add one to the bitmap count to ensure that we search
- * the starting bitmap twice.
- */
- if (rbm->offset != 0)
- iters++;
-
while(1) {
bi = rbm_bi(rbm);
if ((ip == NULL || !gfs2_rs_active(&ip->i_res)) &&
@@ -1761,47 +1751,43 @@ static int gfs2_rbm_find(struct gfs2_rbm *rbm, u8 state, u32 *minext,
WARN_ON(!buffer_uptodate(bh));
if (state != GFS2_BLKST_UNLINKED && bi->bi_clone)
buffer = bi->bi_clone + bi->bi_offset;
- initial_offset = rbm->offset;
offset = gfs2_bitfit(buffer, bi->bi_bytes, rbm->offset, state);
- if (offset == BFITNOENT)
- goto bitmap_full;
+ if (offset == BFITNOENT) {
+ if (state == GFS2_BLKST_FREE && rbm->offset == 0)
+ set_bit(GBF_FULL, &bi->bi_flags);
+ goto next_bitmap;
+ }
rbm->offset = offset;
if (ip == NULL)
return 0;
- initial_bii = rbm->bii;
ret = gfs2_reservation_check_and_update(rbm, ip,
minext ? *minext : 0,
&maxext);
if (ret == 0)
return 0;
- if (ret > 0) {
- n += (rbm->bii - initial_bii);
+ if (ret > 0)
goto next_iter;
- }
if (ret == -E2BIG) {
- n += rbm->bii - initial_bii;
rbm->bii = 0;
rbm->offset = 0;
goto res_covered_end_of_rgrp;
}
return ret;
-bitmap_full: /* Mark bitmap as full and fall through */
- if ((state == GFS2_BLKST_FREE) && initial_offset == 0)
- set_bit(GBF_FULL, &bi->bi_flags);
-
next_bitmap: /* Find next bitmap in the rgrp */
rbm->offset = 0;
rbm->bii++;
if (rbm->bii == rbm->rgd->rd_length)
rbm->bii = 0;
res_covered_end_of_rgrp:
- if ((rbm->bii == 0) && nowrap)
- break;
- n++;
+ if (rbm->bii == 0) {
+ if (nowrap)
+ break;
+ wrapped = true;
+ }
next_iter:
- if (n >= iters)
+ if (wrapped && rbm->bii > first_bii)
break;
}
--
2.20.1
