xfs: track bulkstat progress by agino

The bulkstat main loop progress is tracked by the "lastino"
variable, which is a full 64 bit inode. However, the loop actually
works on agno/agino pairs, and so there's a significant disconnect
between the rest of the loop and the main cursor. Convert this to
use the agino, and pass the agino into the chunk formatting function
and convert it too.

This gets rid of the inconsistency in the loop processing, and
finally makes it simple for us to skip inodes at any point in the
loop simply by incrementing the agino cursor.

cc: <stable@vger.kernel.org> # 3.17
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>

fs/xfs/xfs_itable.c

@@ -282,30 +282,31 @@ xfs_bulkstat_ag_ichunk(
 	bulkstat_one_pf			formatter,
 	size_t				statstruct_size,
 	struct xfs_bulkstat_agichunk	*acp,
-	xfs_ino_t			*lastino)
+	xfs_agino_t			*last_agino)
 {
 	char				__user **ubufp = acp->ac_ubuffer;
 	int				chunkidx;
 	int				error = 0;
-	xfs_agino_t			agino;
+	xfs_agino_t			agino = irbp->ir_startino;
 
-	agino = irbp->ir_startino;
 	for (chunkidx = 0; chunkidx < XFS_INODES_PER_CHUNK;
 	     chunkidx++, agino++) {
 		int		fmterror;
 		int		ubused;
-		xfs_ino_t	ino = XFS_AGINO_TO_INO(mp, agno, agino);
+
+		/* inode won't fit in buffer, we are done */
+		if (acp->ac_ubleft < statstruct_size)
+			break;
 
 		/* Skip if this inode is free */
-		if (XFS_INOBT_MASK(chunkidx) & irbp->ir_free) {
-			*lastino = ino;
+		if (XFS_INOBT_MASK(chunkidx) & irbp->ir_free)
 			continue;
-		}
 
 		/* Get the inode and fill in a single buffer */
 		ubused = statstruct_size;
-		error = formatter(mp, ino, *ubufp, acp->ac_ubleft,
-				  &ubused, &fmterror);
+		error = formatter(mp, XFS_AGINO_TO_INO(mp, agno, agino),
+				  *ubufp, acp->ac_ubleft, &ubused, &fmterror);
+
 		if (fmterror == BULKSTAT_RV_GIVEUP ||
 		    (error && error != -ENOENT && error != -EINVAL)) {
 			acp->ac_ubleft = 0;
@@ -315,20 +316,25 @@ xfs_bulkstat_ag_ichunk(
 
 		/* be careful not to leak error if at end of chunk */
 		if (fmterror == BULKSTAT_RV_NOTHING || error) {
-			*lastino = ino;
 			error = 0;
 			continue;
 		}
 
 		*ubufp += ubused;
 		acp->ac_ubleft -= ubused;
 		acp->ac_ubelem++;
-		*lastino = ino;
-
-		if (acp->ac_ubleft < statstruct_size)
-			break;
 	}
 
+	/*
+	 * Post-update *last_agino. At this point, agino will always point one
+	 * inode past the last inode we processed successfully. Hence we
+	 * substract that inode when setting the *last_agino cursor so that we
+	 * return the correct cookie to userspace. On the next bulkstat call,
+	 * the inode under the lastino cookie will be skipped as we have already
+	 * processed it here.
+	 */
+	*last_agino = agino - 1;
+
 	return error;
 }
 
@@ -352,7 +358,6 @@ xfs_bulkstat(
 	xfs_btree_cur_t		*cur;	/* btree cursor for ialloc btree */
 	size_t			irbsize; /* size of irec buffer in bytes */
 	xfs_inobt_rec_incore_t	*irbuf;	/* start of irec buffer */
-	xfs_ino_t		lastino; /* last inode number returned */
 	int			nirbuf;	/* size of irbuf */
 	int			ubcount; /* size of user's buffer */
 	struct xfs_bulkstat_agichunk ac;
@@ -361,11 +366,10 @@ xfs_bulkstat(
 	/*
 	 * Get the last inode value, see if there's nothing to do.
 	 */
-	lastino = *lastinop;
-	agno = XFS_INO_TO_AGNO(mp, lastino);
-	agino = XFS_INO_TO_AGINO(mp, lastino);
+	agno = XFS_INO_TO_AGNO(mp, *lastinop);
+	agino = XFS_INO_TO_AGINO(mp, *lastinop);
 	if (agno >= mp->m_sb.sb_agcount ||
-	    lastino != XFS_AGINO_TO_INO(mp, agno, agino)) {
+	    *lastinop != XFS_AGINO_TO_INO(mp, agno, agino)) {
 		*done = 1;
 		*ubcountp = 0;
 		return 0;
@@ -420,7 +424,6 @@ xfs_bulkstat(
 				irbp->ir_freecount = r.ir_freecount;
 				irbp->ir_free = r.ir_free;
 				irbp++;
-				agino = r.ir_startino + XFS_INODES_PER_CHUNK;
 			}
 			/* Increment to the next record */
 			error = xfs_btree_increment(cur, 0, &stat);
@@ -458,10 +461,6 @@ xfs_bulkstat(
 				irbp++;
 				icount += XFS_INODES_PER_CHUNK - r.ir_freecount;
 			}
-			/*
-			 * Set agino to after this chunk and bump the cursor.
-			 */
-			agino = r.ir_startino + XFS_INODES_PER_CHUNK;
 			error = xfs_btree_increment(cur, 0, &stat);
 			if (error || stat == 0) {
 				end_of_ag = true;
@@ -481,15 +480,17 @@ xfs_bulkstat(
 		if (error)
 			break;
 		/*
-		 * Now format all the good inodes into the user's buffer.
+		 * Now format all the good inodes into the user's buffer. The
+		 * call to xfs_bulkstat_ag_ichunk() sets up the agino pointer
+		 * for the next loop iteration.
 		 */
 		irbufend = irbp;
 		for (irbp = irbuf;
 		     irbp < irbufend && ac.ac_ubleft >= statstruct_size;
 		     irbp++) {
 			error = xfs_bulkstat_ag_ichunk(mp, agno, irbp,
 					formatter, statstruct_size, &ac,
-					&lastino);
+					&agino);
 			if (error)
 				break;
 
@@ -506,8 +507,7 @@ xfs_bulkstat(
 		if (end_of_ag) {
 			agno++;
 			agino = 0;
-		} else
-			agino = XFS_INO_TO_AGINO(mp, lastino);
+		}
 	}
 	/*
 	 * Done, we're either out of filesystem or space to put the data.
@@ -525,16 +525,13 @@ xfs_bulkstat(
 	if (ac.ac_ubelem)
 		error = 0;
 
-	if (agno >= mp->m_sb.sb_agcount) {
-		/*
-		 * If we ran out of filesystem, mark lastino as off
-		 * the end of the filesystem, so the next call
-		 * will return immediately.
-		 */
-		*lastinop = (xfs_ino_t)XFS_AGINO_TO_INO(mp, agno, 0);
+	/*
+	 * If we ran out of filesystem, lastino will point off the end of
+	 * the filesystem so the next call will return immediately.
+	 */
+	*lastinop = XFS_AGINO_TO_INO(mp, agno, agino);
+	if (agno >= mp->m_sb.sb_agcount)
 		*done = 1;
-	} else
-		*lastinop = (xfs_ino_t)lastino;
 
 	return error;
 }