xfs: factor duplicate code in xfs_alloc_ag_vextent_near into a helper

Add a new xfs_alloc_find_best_extent that does a forward/backward
search in the allocation btree.  That code previously was existed
two times in xfs_alloc_ag_vextent_near, once for each search
direction.

Based on an earlier patch from Dave Chinner.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Alex Elder <aelder@sgi.com>

1 files changed, 113 insertions, 180 deletions

diff --git a/fs/xfs/xfs_alloc.c b/fs/xfs/xfs_alloc.c
index d9133f10d2b1..fa8723f5870a 100644
--- a/fs/xfs/xfs_alloc.c
+++ b/fs/xfs/xfs_alloc.c
@@ -665,6 +665,95 @@ error0:
 }
 
 /*
+ * Search the btree in a given direction via the search cursor and compare
+ * the records found against the good extent we've already found.
+ */
+STATIC int
+xfs_alloc_find_best_extent(
+        struct xfs_alloc_arg    *args,  /* allocation argument structure */
+        struct xfs_btree_cur    **gcur, /* good cursor */
+        struct xfs_btree_cur    **scur, /* searching cursor */
+        xfs_agblock_t           gdiff,  /* difference for search comparison */
+        xfs_agblock_t           *sbno,  /* extent found by search */
+        xfs_extlen_t            *slen,
+        xfs_extlen_t            *slena, /* aligned length */
+        int                     dir)    /* 0 = search right, 1 = search left */
+{
+        xfs_agblock_t           bno;
+        xfs_agblock_t           new;
+        xfs_agblock_t           sdiff;
+        int                     error;
+        int                     i;
+
+        /* The good extent is perfect, no need to  search. */
+        if (!gdiff)
+                goto out_use_good;
+
+        /*
+         * Look until we find a better one, run out of space or run off the end.
+         */
+        do {
+                error = xfs_alloc_get_rec(*scur, sbno, slen, &i);
+                if (error)
+                        goto error0;
+                XFS_WANT_CORRUPTED_GOTO(i == 1, error0);
+                xfs_alloc_compute_aligned(*sbno, *slen, args->alignment,
+                                          args->minlen, &bno, slena);
+
+                /*
+                 * The good extent is closer than this one.
+                 */
+                if (!dir) {
+                        if (bno >= args->agbno + gdiff)
+                                goto out_use_good;
+                } else {
+                        if (bno <= args->agbno - gdiff)
+                                goto out_use_good;
+                }
+
+                /*
+                 * Same distance, compare length and pick the best.
+                 */
+                if (*slena >= args->minlen) {
+                        args->len = XFS_EXTLEN_MIN(*slena, args->maxlen);
+                        xfs_alloc_fix_len(args);
+
+                        sdiff = xfs_alloc_compute_diff(args->agbno, args->len,
+                                                       args->alignment, *sbno,
+                                                       *slen, &new);
+
+                        /*
+                         * Choose closer size and invalidate other cursor.
+                         */
+                        if (sdiff < gdiff)
+                                goto out_use_search;
+                        goto out_use_good;
+                }
+
+                if (!dir)
+                        error = xfs_btree_increment(*scur, 0, &i);
+                else
+                        error = xfs_btree_decrement(*scur, 0, &i);
+                if (error)
+                        goto error0;
+        } while (i);
+
+out_use_good:
+        xfs_btree_del_cursor(*scur, XFS_BTREE_NOERROR);
+        *scur = NULL;
+        return 0;
+
+out_use_search:
+        xfs_btree_del_cursor(*gcur, XFS_BTREE_NOERROR);
+        *gcur = NULL;
+        return 0;
+
+error0:
+        /* caller invalidates cursors */
+        return error;
+}
+
+/*
  * Allocate a variable extent near bno in the allocation group agno.
  * Extent's length (returned in len) will be between minlen and maxlen,
  * and of the form k * prod + mod unless there's nothing that large.
@@ -931,203 +1020,45 @@ xfs_alloc_ag_vextent_near(
                         }
                 }
         } while (bno_cur_lt || bno_cur_gt);
+
         /*
          * Got both cursors still active, need to find better entry.
          */
         if (bno_cur_lt && bno_cur_gt) {
-                /*
-                 * Left side is long enough, look for a right side entry.
-                 */
                 if (ltlena >= args->minlen) {
                         /*
-                         * Fix up the length.
+                         * Left side is good, look for a right side entry.
                          */
                         args->len = XFS_EXTLEN_MIN(ltlena, args->maxlen);
                         xfs_alloc_fix_len(args);
-                        rlen = args->len;
-                        ltdiff = xfs_alloc_compute_diff(args->agbno, rlen,
+                        ltdiff = xfs_alloc_compute_diff(args->agbno, args->len,
                                 args->alignment, ltbno, ltlen, &ltnew);
+
+                        error = xfs_alloc_find_best_extent(args,
+                                                &bno_cur_lt, &bno_cur_gt,
+                                                ltdiff, &gtbno, &gtlen, &gtlena,
+                                                0 /* search right */);
+                } else {
+                        ASSERT(gtlena >= args->minlen);
+
                         /*
-                         * Not perfect.
-                         */
-                        if (ltdiff) {
-                                /*
-                                 * Look until we find a better one, run out of
-                                 * space, or run off the end.
-                                 */
-                                while (bno_cur_lt && bno_cur_gt) {
-                                        if ((error = xfs_alloc_get_rec(
-                                                        bno_cur_gt, &gtbno,
-                                                        &gtlen, &i)))
-                                                goto error0;
-                                        XFS_WANT_CORRUPTED_GOTO(i == 1, error0);
-                                        xfs_alloc_compute_aligned(gtbno, gtlen,
-                                                args->alignment, args->minlen,
-                                                &gtbnoa, &gtlena);
-                                        /*
-                                         * The left one is clearly better.
-                                         */
-                                        if (gtbnoa >= args->agbno + ltdiff) {
-                                                xfs_btree_del_cursor(
-                                                        bno_cur_gt,
-                                                        XFS_BTREE_NOERROR);
-                                                bno_cur_gt = NULL;
-                                                break;
-                                        }
-                                        /*
-                                         * If we reach a big enough entry,
-                                         * compare the two and pick the best.
-                                         */
-                                        if (gtlena >= args->minlen) {
-                                                args->len =
-                                                        XFS_EXTLEN_MIN(gtlena,
-                                                                args->maxlen);
-                                                xfs_alloc_fix_len(args);
-                                                rlen = args->len;
-                                                gtdiff = xfs_alloc_compute_diff(
-                                                        args->agbno, rlen,
-                                                        args->alignment,
-                                                        gtbno, gtlen, &gtnew);
-                                                /*
-                                                 * Right side is better.
-                                                 */
-                                                if (gtdiff < ltdiff) {
-                                                        xfs_btree_del_cursor(
-                                                                bno_cur_lt,
-                                                                XFS_BTREE_NOERROR);
-                                                        bno_cur_lt = NULL;
-                                                }
-                                                /*
-                                                 * Left side is better.
-                                                 */
-                                                else {
-                                                        xfs_btree_del_cursor(
-                                                                bno_cur_gt,
-                                                                XFS_BTREE_NOERROR);
-                                                        bno_cur_gt = NULL;
-                                                }
-                                                break;
-                                        }
-                                        /*
-                                         * Fell off the right end.
-                                         */
-                                        if ((error = xfs_btree_increment(
-                                                        bno_cur_gt, 0, &i)))
-                                                goto error0;
-                                        if (!i) {
-                                                xfs_btree_del_cursor(
-                                                        bno_cur_gt,
-                                                        XFS_BTREE_NOERROR);
-                                                bno_cur_gt = NULL;
-                                                break;
-                                        }
-                                }
-                        }
-                        /*
-                         * The left side is perfect, trash the right side.
-                         */
-                        else {
-                                xfs_btree_del_cursor(bno_cur_gt,
-                                                     XFS_BTREE_NOERROR);
-                                bno_cur_gt = NULL;
-                        }
-                }
-                /*
-                 * It's the right side that was found first, look left.
-                 */
-                else {
-                        /*
-                         * Fix up the length.
+                         * Right side is good, look for a left side entry.
                          */
                         args->len = XFS_EXTLEN_MIN(gtlena, args->maxlen);
                         xfs_alloc_fix_len(args);
-                        rlen = args->len;
-                        gtdiff = xfs_alloc_compute_diff(args->agbno, rlen,
+                        gtdiff = xfs_alloc_compute_diff(args->agbno, args->len,
                                 args->alignment, gtbno, gtlen, &gtnew);
-                        /*
-                         * Right side entry isn't perfect.
-                         */
-                        if (gtdiff) {
-                                /*
-                                 * Look until we find a better one, run out of
-                                 * space, or run off the end.
-                                 */
-                                while (bno_cur_lt && bno_cur_gt) {
-                                        if ((error = xfs_alloc_get_rec(
-                                                        bno_cur_lt, &ltbno,
-                                                        &ltlen, &i)))
-                                                goto error0;
-                                        XFS_WANT_CORRUPTED_GOTO(i == 1, error0);
-                                        xfs_alloc_compute_aligned(ltbno, ltlen,
-                                                args->alignment, args->minlen,
-                                                &ltbnoa, &ltlena);
-                                        /*
-                                         * The right one is clearly better.
-                                         */
-                                        if (ltbnoa <= args->agbno - gtdiff) {
-                                                xfs_btree_del_cursor(
-                                                        bno_cur_lt,
-                                                        XFS_BTREE_NOERROR);
-                                                bno_cur_lt = NULL;
-                                                break;
-                                        }
-                                        /*
-                                         * If we reach a big enough entry,
-                                         * compare the two and pick the best.
-                                         */
-                                        if (ltlena >= args->minlen) {
-                                                args->len = XFS_EXTLEN_MIN(
-                                                        ltlena, args->maxlen);
-                                                xfs_alloc_fix_len(args);
-                                                rlen = args->len;
-                                                ltdiff = xfs_alloc_compute_diff(
-                                                        args->agbno, rlen,
-                                                        args->alignment,
-                                                        ltbno, ltlen, &ltnew);
-                                                /*
-                                                 * Left side is better.
-                                                 */
-                                                if (ltdiff < gtdiff) {
-                                                        xfs_btree_del_cursor(
-                                                                bno_cur_gt,
-                                                                XFS_BTREE_NOERROR);
-                                                        bno_cur_gt = NULL;
-                                                }
-                                                /*
-                                                 * Right side is better.
-                                                 */
-                                                else {
-                                                        xfs_btree_del_cursor(
-                                                                bno_cur_lt,
-                                                                XFS_BTREE_NOERROR);
-                                                        bno_cur_lt = NULL;
-                                                }
-                                                break;
-                                        }
-                                        /*
-                                         * Fell off the left end.
-                                         */
-                                        if ((error = xfs_btree_decrement(
-                                                        bno_cur_lt, 0, &i)))
-                                                goto error0;
-                                        if (!i) {
-                                                xfs_btree_del_cursor(bno_cur_lt,
-                                                        XFS_BTREE_NOERROR);
-                                                bno_cur_lt = NULL;
-                                                break;
-                                        }
-                                }
-                        }
-                        /*
-                         * The right side is perfect, trash the left side.
-                         */
-                        else {
-                                xfs_btree_del_cursor(bno_cur_lt,
-                                        XFS_BTREE_NOERROR);
-                                bno_cur_lt = NULL;
-                        }
+
+                        error = xfs_alloc_find_best_extent(args,
+                                                &bno_cur_gt, &bno_cur_lt,
+                                                gtdiff, &ltbno, &ltlen, &ltlena,
+                                                1 /* search left */);
                 }
+
+                if (error)
+                        goto error0;
         }
+
         /*
          * If we couldn't get anything, give up.
          */
@@ -1136,6 +1067,7 @@ xfs_alloc_ag_vextent_near(
                 args->agbno = NULLAGBLOCK;
                 return 0;
         }
+
         /*
          * At this point we have selected a freespace entry, either to the
          * left or to the right.  If it's on the right, copy all the
@@ -1152,6 +1084,7 @@ xfs_alloc_ag_vextent_near(
                 j = 1;
         } else
                 j = 0;
+
         /*
          * Fix up the length and compute the useful address.
          */