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[PATCH 3/6] xfs: bulkstat chunk-formatter has issues

To: xfs@xxxxxxxxxxx
Subject: [PATCH 3/6] xfs: bulkstat chunk-formatter has issues
From: Dave Chinner <david@xxxxxxxxxxxxx>
Date: Tue, 4 Nov 2014 23:53:18 +1100
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <1415105601-6455-1-git-send-email-david@xxxxxxxxxxxxx>
References: <1415105601-6455-1-git-send-email-david@xxxxxxxxxxxxx>
From: Dave Chinner <dchinner@xxxxxxxxxx>

The loop construct has issues:
        - clustidx is completely unused, so remove it.
        - the loop tries to be smart by terminating when the
          "freecount" tells it that all inodes are free. Just drop
          it as in most cases we have to scan all inodes in the
          chunk anyway.
        - move the "user buffer left" condition check to the only
          point where we consume space int eh user buffer.
        - move the initialisation of agino out of the loop, leaving
          just a simple loop control logic using the clusteridx.

Also, double handling of the user buffer variables leads to problems
tracking the current state - use the cursor variables directly
rather than keeping local copies and then having to update the
cursor before returning.

cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Dave Chinner <dchinner@xxxxxxxxxx>
---
 fs/xfs/xfs_itable.c | 55 ++++++++++++++++++++---------------------------------
 1 file changed, 21 insertions(+), 34 deletions(-)

diff --git a/fs/xfs/xfs_itable.c b/fs/xfs/xfs_itable.c
index 50a3e59..ff31965 100644
--- a/fs/xfs/xfs_itable.c
+++ b/fs/xfs/xfs_itable.c
@@ -283,59 +283,46 @@ xfs_bulkstat_ag_ichunk(
        xfs_ino_t                       *lastino)
 {
        char                            __user **ubufp = acp->ac_ubuffer;
-       int                             ubleft = acp->ac_ubleft;
-       int                             ubelem = acp->ac_ubelem;
-       int                             chunkidx, clustidx;
+       int                             chunkidx;
        int                             error = 0;
        xfs_agino_t                     agino;
 
-       for (agino = irbp->ir_startino, chunkidx = clustidx = 0;
-            XFS_BULKSTAT_UBLEFT(ubleft) &&
-            irbp->ir_freecount < XFS_INODES_PER_CHUNK;
-            chunkidx++, clustidx++, agino++) {
-               int             fmterror;       /* bulkstat formatter result */
+       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);
 
-               ASSERT(chunkidx < XFS_INODES_PER_CHUNK);
-
                /* Skip if this inode is free */
                if (XFS_INOBT_MASK(chunkidx) & irbp->ir_free) {
                        *lastino = ino;
                        continue;
                }
 
-               /*
-                * Count used inodes as free so we can tell when the
-                * chunk is used up.
-                */
-               irbp->ir_freecount++;
-
                /* Get the inode and fill in a single buffer */
                ubused = statstruct_size;
-               error = formatter(mp, ino, *ubufp, ubleft, &ubused, &fmterror);
-               if (fmterror == BULKSTAT_RV_NOTHING) {
-                       if (error && error != -ENOENT && error != -EINVAL) {
-                               ubleft = 0;
-                               break;
-                       }
-                       *lastino = ino;
-                       continue;
-               }
-               if (fmterror == BULKSTAT_RV_GIVEUP) {
-                       ubleft = 0;
+               error = formatter(mp, ino, *ubufp, acp->ac_ubleft,
+                                 &ubused, &fmterror);
+               if (fmterror == BULKSTAT_RV_GIVEUP ||
+                   (error && error != -ENOENT && error != -EINVAL)) {
+                       acp->ac_ubleft = 0;
                        ASSERT(error);
                        break;
                }
-               if (*ubufp)
-                       *ubufp += ubused;
-               ubleft -= ubused;
-               ubelem++;
+               if (fmterror == BULKSTAT_RV_NOTHING || error) {
+                       *lastino = ino;
+                       continue;
+               }
+
+               *ubufp += ubused;
+               acp->ac_ubleft -= ubused;
+               acp->ac_ubelem++;
                *lastino = ino;
-       }
 
-       acp->ac_ubleft = ubleft;
-       acp->ac_ubelem = ubelem;
+               if (acp->ac_ubleft < statstruct_size)
+                       break;
+       }
 
        return error;
 }
-- 
2.0.0

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