xfs: rewrite xfs_bmap_first_unused to make better use of xfs_iext_get_extent

Look at the return value of xfs_iext_get_extent instead of figuring out
the extent count first and looping up to it.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>

diff --git a/fs/xfs/libxfs/xfs_bmap.c b/fs/xfs/libxfs/xfs_bmap.c
index e77a71c..bf23de8 100644 (file)
--- a/fs/xfs/libxfs/xfs_bmap.c
+++ b/fs/xfs/libxfs/xfs_bmap.c
@@ -1285,57 +1285,53 @@ error0:
 }
 
 /*
- * Returns the file-relative block number of the first unused block(s)
- * in the file with at least "len" logically contiguous blocks free.
- * This is the lowest-address hole if the file has holes, else the first block
- * past the end of file.
- * Return 0 if the file is currently local (in-inode).
+ * Returns the relative block number of the first unused block(s) in the given
+ * fork with at least "len" logically contiguous blocks free.  This is the
+ * lowest-address hole if the fork has holes, else the first block past the end
+ * of fork.  Return 0 if the fork is currently local (in-inode).
  */
 int                                            /* error */
 xfs_bmap_first_unused(
-       xfs_trans_t     *tp,                    /* transaction pointer */
-       xfs_inode_t     *ip,                    /* incore inode */
-       xfs_extlen_t    len,                    /* size of hole to find */
-       xfs_fileoff_t   *first_unused,          /* unused block */
-       int             whichfork)              /* data or attr fork */
+       struct xfs_trans        *tp,            /* transaction pointer */
+       struct xfs_inode        *ip,            /* incore inode */
+       xfs_extlen_t            len,            /* size of hole to find */
+       xfs_fileoff_t           *first_unused,  /* unused block */
+       int                     whichfork)      /* data or attr fork */
 {
-       int             error;                  /* error return value */
-       int             idx;                    /* extent record index */
-       xfs_ifork_t     *ifp;                   /* inode fork pointer */
-       xfs_fileoff_t   lastaddr;               /* last block number seen */
-       xfs_fileoff_t   lowest;                 /* lowest useful block */
-       xfs_fileoff_t   max;                    /* starting useful block */
-       xfs_extnum_t    nextents;               /* number of extent entries */
+       struct xfs_ifork        *ifp = XFS_IFORK_PTR(ip, whichfork);
+       struct xfs_bmbt_irec    got;
+       xfs_extnum_t            idx = 0;
+       xfs_fileoff_t           lastaddr = 0;
+       xfs_fileoff_t           lowest, max;
+       int                     error;
 
        ASSERT(XFS_IFORK_FORMAT(ip, whichfork) == XFS_DINODE_FMT_BTREE ||
               XFS_IFORK_FORMAT(ip, whichfork) == XFS_DINODE_FMT_EXTENTS ||
               XFS_IFORK_FORMAT(ip, whichfork) == XFS_DINODE_FMT_LOCAL);
+
        if (XFS_IFORK_FORMAT(ip, whichfork) == XFS_DINODE_FMT_LOCAL) {
                *first_unused = 0;
                return 0;
        }
-       ifp = XFS_IFORK_PTR(ip, whichfork);
-       if (!(ifp->if_flags & XFS_IFEXTENTS) &&
-           (error = xfs_iread_extents(tp, ip, whichfork)))
-               return error;
-       lowest = *first_unused;
-       nextents = xfs_iext_count(ifp);
-       for (idx = 0, lastaddr = 0, max = lowest; idx < nextents; idx++) {
-               struct xfs_bmbt_irec got;
 
-               xfs_iext_get_extent(ifp, idx, &got);
+       if (!(ifp->if_flags & XFS_IFEXTENTS)) {
+               error = xfs_iread_extents(tp, ip, whichfork);
+               if (error)
+                       return error;
+       }
 
+       lowest = max = *first_unused;
+       while (xfs_iext_get_extent(ifp, idx++, &got)) {
                /*
                 * See if the hole before this extent will work.
                 */
                if (got.br_startoff >= lowest + len &&
-                   got.br_startoff - max >= len) {
-                       *first_unused = max;
-                       return 0;
-               }
+                   got.br_startoff - max >= len)
+                       break;
                lastaddr = got.br_startoff + got.br_blockcount;
                max = XFS_FILEOFF_MAX(lastaddr, lowest);
        }
+
        *first_unused = max;
        return 0;
 }