xfs: refactor xfs_iwalk_grab_ichunk

In preparation for reusing the iwalk code for the inogrp walking code
(aka INUMBERS), move the initial inobt lookup and retrieval code out of
xfs_iwalk_grab_ichunk so that we call the masking code only when we need
to trim out the inodes that came before the cursor in the inobt record
(aka BULKSTAT).
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>

fs/xfs/xfs_iwalk.c

@@ -98,43 +98,17 @@ xfs_iwalk_ichunk_ra(
 }
 
 /*
- * Lookup the inode chunk that the given @agino lives in and then get the
- * record if we found the chunk.  Set the bits in @irec's free mask that
- * correspond to the inodes before @agino so that we skip them.  This is how we
- * restart an inode walk that was interrupted in the middle of an inode record.
+ * Set the bits in @irec's free mask that correspond to the inodes before
+ * @agino so that we skip them.  This is how we restart an inode walk that was
+ * interrupted in the middle of an inode record.
  */
-STATIC int
-xfs_iwalk_grab_ichunk(
-	struct xfs_btree_cur		*cur,	/* btree cursor */
+STATIC void
+xfs_iwalk_adjust_start(
 	xfs_agino_t			agino,	/* starting inode of chunk */
-	int				*icount,/* return # of inodes grabbed */
 	struct xfs_inobt_rec_incore	*irec)	/* btree record */
 {
 	int				idx;	/* index into inode chunk */
-	int				stat;
 	int				i;
-	int				error = 0;
-
-	/* Lookup the inode chunk that this inode lives in */
-	error = xfs_inobt_lookup(cur, agino, XFS_LOOKUP_LE, &stat);
-	if (error)
-		return error;
-	if (!stat) {
-		*icount = 0;
-		return error;
-	}
-
-	/* Get the record, should always work */
-	error = xfs_inobt_get_rec(cur, irec, &stat);
-	if (error)
-		return error;
-	XFS_WANT_CORRUPTED_RETURN(cur->bc_mp, stat == 1);
-
-	/* Check if the record contains the inode in request */
-	if (irec->ir_startino + XFS_INODES_PER_CHUNK <= agino) {
-		*icount = 0;
-		return 0;
-	}
 
 	idx = agino - irec->ir_startino;
 
@@ -149,8 +123,6 @@ xfs_iwalk_grab_ichunk(
 	}
 
 	irec->ir_free |= xfs_inobt_maskn(0, idx);
-	*icount = irec->ir_count - irec->ir_freecount;
-	return 0;
 }
 
 /* Allocate memory for a walk. */
@@ -259,7 +231,7 @@ xfs_iwalk_ag_start(
 {
 	struct xfs_mount	*mp = iwag->mp;
 	struct xfs_trans	*tp = iwag->tp;
-	int			icount;
+	struct xfs_inobt_rec_incore *irec;
 	int			error;
 
 	/* Set up a fresh cursor and empty the inobt cache. */
@@ -275,15 +247,40 @@ xfs_iwalk_ag_start(
 	/*
 	 * Otherwise, we have to grab the inobt record where we left off, stuff
 	 * the record into our cache, and then see if there are more records.
-	 * We require a lookup cache of at least two elements so that we don't
-	 * have to deal with tearing down the cursor to walk the records.
+	 * We require a lookup cache of at least two elements so that the
+	 * caller doesn't have to deal with tearing down the cursor to walk the
+	 * records.
 	 */
-	error = xfs_iwalk_grab_ichunk(*curpp, agino, &icount,
-			&iwag->recs[iwag->nr_recs]);
+	error = xfs_inobt_lookup(*curpp, agino, XFS_LOOKUP_LE, has_more);
 	if (error)
 		return error;
-	if (icount)
-		iwag->nr_recs++;
+
+	/*
+	 * If the LE lookup at @agino yields no records, jump ahead to the
+	 * inobt cursor increment to see if there are more records to process.
+	 */
+	if (!*has_more)
+		goto out_advance;
+
+	/* Get the record, should always work */
+	irec = &iwag->recs[iwag->nr_recs];
+	error = xfs_inobt_get_rec(*curpp, irec, has_more);
+	if (error)
+		return error;
+	XFS_WANT_CORRUPTED_RETURN(mp, *has_more == 1);
+
+	/*
+	 * If the LE lookup yielded an inobt record before the cursor position,
+	 * skip it and see if there's another one after it.
+	 */
+	if (irec->ir_startino + XFS_INODES_PER_CHUNK <= agino)
+		goto out_advance;
+
+	/*
+	 * If agino fell in the middle of the inode record, make it look like
+	 * the inodes up to agino are free so that we don't return them again.
+	 */
+	xfs_iwalk_adjust_start(agino, irec);
 
 	/*
 	 * The prefetch calculation is supposed to give us a large enough inobt
@@ -291,8 +288,10 @@ xfs_iwalk_ag_start(
 	 * the loop body can cache a record without having to check for cache
 	 * space until after it reads an inobt record.
 	 */
+	iwag->nr_recs++;
 	ASSERT(iwag->nr_recs < iwag->sz_recs);
 
+out_advance:
 	return xfs_btree_increment(*curpp, 0, has_more);
 }