xfs: untangle xfs_dialloc

Clarify the control flow in xfs_dialloc.  Factor out a helper to go to the
next node from the current one and improve the control flow by expanding
composite if statements and using gotos.

The xfs_ialloc_next_rec helper is borrowed from Dave Chinners dynamic
allocation policy patches.

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

1 files changed, 138 insertions, 153 deletions

diff --git a/fs/xfs/xfs_ialloc.c b/fs/xfs/xfs_ialloc.c
index 18bf6eece54d..7679c1633053 100644
--- a/fs/xfs/xfs_ialloc.c
+++ b/fs/xfs/xfs_ialloc.c
@@ -589,6 +589,37 @@ nextag:
         }
 }
 
+/*
+ * Try to retrieve the next record to the left/right from the current one.
+ */
+STATIC int
+xfs_ialloc_next_rec(
+        struct xfs_btree_cur    *cur,
+        xfs_inobt_rec_incore_t  *rec,
+        int                     *done,
+        int                     left)
+{
+        int                     error;
+        int                     i;
+
+        if (left)
+                error = xfs_btree_decrement(cur, 0, &i);
+        else
+                error = xfs_btree_increment(cur, 0, &i);
+
+        if (error)
+                return error;
+        *done = !i;
+        if (i) {
+                error = xfs_inobt_get_rec(cur, rec, &i);
+                if (error)
+                        return error;
+                XFS_WANT_CORRUPTED_RETURN(i == 1);
+        }
+
+        return 0;
+}
+
 
 /*
  * Visible inode allocation functions.
@@ -644,8 +675,8 @@ xfs_dialloc(
         int             j;              /* result code */
         xfs_mount_t     *mp;            /* file system mount structure */
         int             offset;         /* index of inode in chunk */
-        xfs_agino_t     pagino;         /* parent's a.g. relative inode # */
-        xfs_agnumber_t  pagno;          /* parent's allocation group number */
+        xfs_agino_t     pagino;         /* parent's AG relative inode # */
+        xfs_agnumber_t  pagno;          /* parent's AG number */
         xfs_inobt_rec_incore_t rec;     /* inode allocation record */
         xfs_agnumber_t  tagno;          /* testing allocation group number */
         xfs_btree_cur_t *tcur;          /* temp cursor */
@@ -781,186 +812,140 @@ nextag:
                 goto error0;
 
         /*
-         * If in the same a.g. as the parent, try to get near the parent.
+         * If in the same AG as the parent, try to get near the parent.
          */
         if (pagno == agno) {
-                if ((error = xfs_inobt_lookup_le(cur, pagino, 0, 0, &i)))
+                int             doneleft;       /* done, to the left */
+                int             doneright;      /* done, to the right */
+
+                error = xfs_inobt_lookup_le(cur, pagino, 0, 0, &i);
+                if (error)
+                        goto error0;
+                XFS_WANT_CORRUPTED_GOTO(i == 1, error0);
+
+                error = xfs_inobt_get_rec(cur, &rec, &j);
+                if (error)
                         goto error0;
-                if (i != 0 &&
-                    (error = xfs_inobt_get_rec(cur, &rec, &j)) == 0 &&
-                    j == 1 &&
-                    rec.ir_freecount > 0) {
+                XFS_WANT_CORRUPTED_GOTO(i == 1, error0);
+
+                if (rec.ir_freecount > 0) {
                         /*
                          * Found a free inode in the same chunk
-                         * as parent, done.
+                         * as the parent, done.
                          */
+                        goto alloc_inode;
                 }
+
+
                 /*
-                 * In the same a.g. as parent, but parent's chunk is full.
+                 * In the same AG as parent, but parent's chunk is full.
                  */
-                else {
-                        int     doneleft;       /* done, to the left */
-                        int     doneright;      /* done, to the right */
 
-                        if (error)
-                                goto error0;
-                        ASSERT(i == 1);
-                        ASSERT(j == 1);
-                        /*
-                         * Duplicate the cursor, search left & right
-                         * simultaneously.
-                         */
-                        if ((error = xfs_btree_dup_cursor(cur, &tcur)))
-                                goto error0;
-                        /*
-                         * Search left with tcur, back up 1 record.
-                         */
-                        if ((error = xfs_btree_decrement(tcur, 0, &i)))
-                                goto error1;
-                        doneleft = !i;
-                        if (!doneleft) {
-                                error = xfs_inobt_get_rec(tcur, &trec, &i);
-                                if (error)
-                                        goto error1;
-                                XFS_WANT_CORRUPTED_GOTO(i == 1, error1);
+                /* duplicate the cursor, search left & right simultaneously */
+                error = xfs_btree_dup_cursor(cur, &tcur);
+                if (error)
+                        goto error0;
+
+                /* search left with tcur, back up 1 record */
+                error = xfs_ialloc_next_rec(tcur, &trec, &doneleft, 1);
+                if (error)
+                        goto error1;
+
+                /* search right with cur, go forward 1 record. */
+                error = xfs_ialloc_next_rec(cur, &rec, &doneright, 0);
+                if (error)
+                        goto error1;
+
+                /*
+                 * Loop until we find an inode chunk with a free inode.
+                 */
+                while (!doneleft || !doneright) {
+                        int     useleft;  /* using left inode chunk this time */
+
+                        /* figure out the closer block if both are valid. */
+                        if (!doneleft && !doneright) {
+                                useleft = pagino -
+                                 (trec.ir_startino + XFS_INODES_PER_CHUNK - 1) <
+                                  rec.ir_startino - pagino;
+                        } else {
+                                useleft = !doneleft;
                         }
-                        /*
-                         * Search right with cur, go forward 1 record.
-                         */
-                        if ((error = xfs_btree_increment(cur, 0, &i)))
-                                goto error1;
-                        doneright = !i;
-                        if (!doneright) {
-                                error = xfs_inobt_get_rec(cur, &rec, &i);
-                                if (error)
-                                        goto error1;
-                                XFS_WANT_CORRUPTED_GOTO(i == 1, error1);
+
+                        /* free inodes to the left? */
+                        if (useleft && trec.ir_freecount) {
+                                rec = trec;
+                                xfs_btree_del_cursor(cur, XFS_BTREE_NOERROR);
+                                cur = tcur;
+                                goto alloc_inode;
                         }
-                        /*
-                         * Loop until we find the closest inode chunk
-                         * with a free one.
-                         */
-                        while (!doneleft || !doneright) {
-                                int     useleft;  /* using left inode
-                                                     chunk this time */
 
-                                /*
-                                 * Figure out which block is closer,
-                                 * if both are valid.
-                                 */
-                                if (!doneleft && !doneright)
-                                        useleft =
-                                                pagino -
-                                                (trec.ir_startino +
-                                                 XFS_INODES_PER_CHUNK - 1) <
-                                                 rec.ir_startino - pagino;
-                                else
-                                        useleft = !doneleft;
-                                /*
-                                 * If checking the left, does it have
-                                 * free inodes?
-                                 */
-                                if (useleft && trec.ir_freecount) {
-                                        /*
-                                         * Yes, set it up as the chunk to use.
-                                         */
-                                        rec = trec;
-                                        xfs_btree_del_cursor(cur,
-                                                XFS_BTREE_NOERROR);
-                                        cur = tcur;
-                                        break;
-                                }
-                                /*
-                                 * If checking the right, does it have
-                                 * free inodes?
-                                 */
-                                if (!useleft && rec.ir_freecount) {
-                                        /*
-                                         * Yes, it's already set up.
-                                         */
-                                        xfs_btree_del_cursor(tcur,
-                                                XFS_BTREE_NOERROR);
-                                        break;
-                                }
-                                /*
-                                 * If used the left, get another one
-                                 * further left.
-                                 */
-                                if (useleft) {
-                                        if ((error = xfs_btree_decrement(tcur, 0,
-                                                        &i)))
-                                                goto error1;
-                                        doneleft = !i;
-                                        if (!doneleft) {
-                                                error = xfs_inobt_get_rec(
-                                                            tcur, &trec, &i);
-                                                if (error)
-                                                        goto error1;
-                                                XFS_WANT_CORRUPTED_GOTO(i == 1,
-                                                        error1);
-                                        }
-                                }
-                                /*
-                                 * If used the right, get another one
-                                 * further right.
-                                 */
-                                else {
-                                        if ((error = xfs_btree_increment(cur, 0,
-                                                        &i)))
-                                                goto error1;
-                                        doneright = !i;
-                                        if (!doneright) {
-                                                error = xfs_inobt_get_rec(
-                                                            cur, &rec, &i);
-                                                if (error)
-                                                        goto error1;
-                                                XFS_WANT_CORRUPTED_GOTO(i == 1,
-                                                        error1);
-                                        }
-                                }
+                        /* free inodes to the right? */
+                        if (!useleft && rec.ir_freecount) {
+                                xfs_btree_del_cursor(tcur, XFS_BTREE_NOERROR);
+                                goto alloc_inode;
                         }
-                        ASSERT(!doneleft || !doneright);
+
+                        /* get next record to check */
+                        if (useleft) {
+                                error = xfs_ialloc_next_rec(tcur, &trec,
+                                                                 &doneleft, 1);
+                        } else {
+                                error = xfs_ialloc_next_rec(cur, &rec,
+                                                                 &doneright, 0);
+                        }
+                        if (error)
+                                goto error1;
                 }
+                ASSERT(!doneleft || !doneright);
         }
+
         /*
-         * In a different a.g. from the parent.
+         * In a different AG from the parent.
          * See if the most recently allocated block has any free.
          */
         else if (be32_to_cpu(agi->agi_newino) != NULLAGINO) {
-                if ((error = xfs_inobt_lookup_eq(cur,
-                                be32_to_cpu(agi->agi_newino), 0, 0, &i)))
+                error = xfs_inobt_lookup_eq(cur, be32_to_cpu(agi->agi_newino),
+                                            0, 0, &i);
+                if (error)
                         goto error0;
-                if (i == 1 &&
-                    (error = xfs_inobt_get_rec(cur, &rec, &j)) == 0 &&
-                    j == 1 &&
-                    rec.ir_freecount > 0) {
-                        /*
-                         * The last chunk allocated in the group still has
-                         * a free inode.
-                         */
+
+                if (i == 1) {
+                        error = xfs_inobt_get_rec(cur, &rec, &j);
+                        if (error)
+                                goto error0;
+
+                        if (j == 1 && rec.ir_freecount > 0) {
+                                /*
+                                 * The last chunk allocated in the group
+                                 * still has a free inode.
+                                 */
+                                goto alloc_inode;
+                        }
                 }
+
                 /*
-                 * None left in the last group, search the whole a.g.
+                 * None left in the last group, search the whole AG
                  */
-                else {
+                error = xfs_inobt_lookup_ge(cur, 0, 0, 0, &i);
+                if (error)
+                        goto error0;
+                XFS_WANT_CORRUPTED_GOTO(i == 1, error0);
+
+                for (;;) {
+                        error = xfs_inobt_get_rec(cur, &rec, &i);
                         if (error)
                                 goto error0;
-                        if ((error = xfs_inobt_lookup_ge(cur, 0, 0, 0, &i)))
+                        XFS_WANT_CORRUPTED_GOTO(i == 1, error0);
+                        if (rec.ir_freecount > 0)
+                                break;
+                        error = xfs_btree_increment(cur, 0, &i);
+                        if (error)
                                 goto error0;
-                        ASSERT(i == 1);
-                        for (;;) {
-                                error = xfs_inobt_get_rec(cur, &rec, &i);
-                                if (error)
-                                        goto error0;
-                                XFS_WANT_CORRUPTED_GOTO(i == 1, error0);
-                                if (rec.ir_freecount > 0)
-                                        break;
-                                if ((error = xfs_btree_increment(cur, 0, &i)))
-                                        goto error0;
-                                XFS_WANT_CORRUPTED_GOTO(i == 1, error0);
-                        }
+                        XFS_WANT_CORRUPTED_GOTO(i == 1, error0);
                 }
         }
+
+alloc_inode:
         offset = xfs_ialloc_find_free(&rec.ir_free);
         ASSERT(offset >= 0);
         ASSERT(offset < XFS_INODES_PER_CHUNK);