On Mon, May 21, 2012 at 05:10:50PM -0500, Eric Sandeen wrote: > blkmap_next_off() was cryptic (to me), so document what it does. > Also catch cases when the passed in extent index 't' is beyond > the number of extents in the blkmap, so that: > > ext = blkmap->exts + *t; > > doesn't walk off the end of the array into garbage. > > Signed-off-by: Eric Sandeen <sandeen@xxxxxxxxxx> > --- > > diff --git a/repair/bmap.c b/repair/bmap.c > index c43ca7f..85d66dc 100644 > --- a/repair/bmap.c > +++ b/repair/bmap.c > @@ -206,8 +206,25 @@ blkmap_last_off( > return ext->startoff + ext->blockcount; > } > > -/* > - * Return the next offset in a block map. > +/** > + * blkmap_next_off - Return next logical block offset in a block map. > + * @blkmap: blockmap to use > + * @o: current file logical block number > + * @t: current extent index into blockmap (in/out) > + * > + * Given a logical block offset in a file, return the next mapped logical offset > + * The map index "t" tracks the current extent number in the block map, and > + * is updated automatically if the returned offset resides within the next > + * mapped extent. > + * > + * If the blockmap contains no extents, or no more logical offsets are mapped, > + * or the extent index exceeds the number of extents in the map, > + * return NULLDFILOFF. > + * > + * If offset o is beyond extent index t, the first offset in the next extent > + * after extent t will be returned. > + * > + * Intended to be called starting with offset 0, index 0, and iterated. > */ > xfs_dfiloff_t > blkmap_next_off( > @@ -223,10 +240,12 @@ blkmap_next_off( > *t = 0; > return blkmap->exts[0].startoff; > } > + if (*t >= blkmap->nexts) > + return NULLDFILOFF; > ext = blkmap->exts + *t; > if (o < ext->startoff + ext->blockcount - 1) > return o + 1; > - if (*t >= blkmap->nexts - 1) > + if (*t == blkmap->nexts - 1) > return NULLDFILOFF; > (*t)++; > return ext[1].startoff; Ok, so you have 50 extents, and when *t == 49 you don't want to go looking at ext[50].startoff. Looks good to me. Reviewed-by: Ben Myers <bpm@xxxxxxx> _______________________________________________ xfs mailing list xfs@xxxxxxxxxxx http://oss.sgi.com/mailman/listinfo/xfs
