From: Andreas Gruenbacher agruenba@redhat.com
commit a27a0c9b6a208722016c8ec5ad31ec96082b91ec upstream.
It turns out that the current version of gfs2_metadata_walker suffers from multiple problems that can cause gfs2_hole_size to report an incorrect size. This will confuse fiemap as well as lseek with the SEEK_DATA flag.
Fix that by changing gfs2_hole_walker to compute the metapath to the first data block after the hole (if any), and compute the hole size based on that.
Fixes xfstest generic/490.
Signed-off-by: Andreas Gruenbacher agruenba@redhat.com Reviewed-by: Bob Peterson rpeterso@redhat.com Cc: stable@vger.kernel.org # v4.18+ Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- fs/gfs2/bmap.c | 168 ++++++++++++++++++++++++++++++++++----------------------- 1 file changed, 103 insertions(+), 65 deletions(-)
--- a/fs/gfs2/bmap.c +++ b/fs/gfs2/bmap.c @@ -390,6 +390,19 @@ static int fillup_metapath(struct gfs2_i return mp->mp_aheight - x - 1; }
+static sector_t metapath_to_block(struct gfs2_sbd *sdp, struct metapath *mp) +{ + sector_t factor = 1, block = 0; + int hgt; + + for (hgt = mp->mp_fheight - 1; hgt >= 0; hgt--) { + if (hgt < mp->mp_aheight) + block += mp->mp_list[hgt] * factor; + factor *= sdp->sd_inptrs; + } + return block; +} + static void release_metapath(struct metapath *mp) { int i; @@ -430,60 +443,84 @@ static inline unsigned int gfs2_extent_l return ptr - first; }
-typedef const __be64 *(*gfs2_metadata_walker)( - struct metapath *mp, - const __be64 *start, const __be64 *end, - u64 factor, void *data); - -#define WALK_STOP ((__be64 *)0) -#define WALK_NEXT ((__be64 *)1) - -static int gfs2_walk_metadata(struct inode *inode, sector_t lblock, - u64 len, struct metapath *mp, gfs2_metadata_walker walker, - void *data) +enum walker_status { WALK_STOP, WALK_FOLLOW, WALK_CONTINUE }; + +/* + * gfs2_metadata_walker - walk an indirect block + * @mp: Metapath to indirect block + * @ptrs: Number of pointers to look at + * + * When returning WALK_FOLLOW, the walker must update @mp to point at the right + * indirect block to follow. + */ +typedef enum walker_status (*gfs2_metadata_walker)(struct metapath *mp, + unsigned int ptrs); + +/* + * gfs2_walk_metadata - walk a tree of indirect blocks + * @inode: The inode + * @mp: Starting point of walk + * @max_len: Maximum number of blocks to walk + * @walker: Called during the walk + * + * Returns 1 if the walk was stopped by @walker, 0 if we went past @max_len or + * past the end of metadata, and a negative error code otherwise. + */ + +static int gfs2_walk_metadata(struct inode *inode, struct metapath *mp, + u64 max_len, gfs2_metadata_walker walker) { - struct metapath clone; struct gfs2_inode *ip = GFS2_I(inode); struct gfs2_sbd *sdp = GFS2_SB(inode); - const __be64 *start, *end, *ptr; u64 factor = 1; unsigned int hgt; - int ret = 0; + int ret;
- for (hgt = ip->i_height - 1; hgt >= mp->mp_aheight; hgt--) + /* + * The walk starts in the lowest allocated indirect block, which may be + * before the position indicated by @mp. Adjust @max_len accordingly + * to avoid a short walk. + */ + for (hgt = mp->mp_fheight - 1; hgt >= mp->mp_aheight; hgt--) { + max_len += mp->mp_list[hgt] * factor; + mp->mp_list[hgt] = 0; factor *= sdp->sd_inptrs; + }
for (;;) { - u64 step; + u16 start = mp->mp_list[hgt]; + enum walker_status status; + unsigned int ptrs; + u64 len;
/* Walk indirect block. */ - start = metapointer(hgt, mp); - end = metaend(hgt, mp); - - step = (end - start) * factor; - if (step > len) - end = start + DIV_ROUND_UP_ULL(len, factor); - - ptr = walker(mp, start, end, factor, data); - if (ptr == WALK_STOP) + ptrs = (hgt >= 1 ? sdp->sd_inptrs : sdp->sd_diptrs) - start; + len = ptrs * factor; + if (len > max_len) + ptrs = DIV_ROUND_UP_ULL(max_len, factor); + status = walker(mp, ptrs); + switch (status) { + case WALK_STOP: + return 1; + case WALK_FOLLOW: + BUG_ON(mp->mp_aheight == mp->mp_fheight); + ptrs = mp->mp_list[hgt] - start; + len = ptrs * factor; break; - if (step >= len) + case WALK_CONTINUE: break; - len -= step; - if (ptr != WALK_NEXT) { - BUG_ON(!*ptr); - mp->mp_list[hgt] += ptr - start; - goto fill_up_metapath; } + if (len >= max_len) + break; + max_len -= len; + if (status == WALK_FOLLOW) + goto fill_up_metapath;
lower_metapath: /* Decrease height of metapath. */ - if (mp != &clone) { - clone_metapath(&clone, mp); - mp = &clone; - } brelse(mp->mp_bh[hgt]); mp->mp_bh[hgt] = NULL; + mp->mp_list[hgt] = 0; if (!hgt) break; hgt--; @@ -491,10 +528,7 @@ lower_metapath:
/* Advance in metadata tree. */ (mp->mp_list[hgt])++; - start = metapointer(hgt, mp); - end = metaend(hgt, mp); - if (start >= end) { - mp->mp_list[hgt] = 0; + if (mp->mp_list[hgt] >= sdp->sd_inptrs) { if (!hgt) break; goto lower_metapath; @@ -502,44 +536,36 @@ lower_metapath:
fill_up_metapath: /* Increase height of metapath. */ - if (mp != &clone) { - clone_metapath(&clone, mp); - mp = &clone; - } ret = fillup_metapath(ip, mp, ip->i_height - 1); if (ret < 0) - break; + return ret; hgt += ret; for (; ret; ret--) do_div(factor, sdp->sd_inptrs); mp->mp_aheight = hgt + 1; } - if (mp == &clone) - release_metapath(mp); - return ret; + return 0; }
-struct gfs2_hole_walker_args { - u64 blocks; -}; - -static const __be64 *gfs2_hole_walker(struct metapath *mp, - const __be64 *start, const __be64 *end, - u64 factor, void *data) +static enum walker_status gfs2_hole_walker(struct metapath *mp, + unsigned int ptrs) { - struct gfs2_hole_walker_args *args = data; - const __be64 *ptr; + const __be64 *start, *ptr, *end; + unsigned int hgt; + + hgt = mp->mp_aheight - 1; + start = metapointer(hgt, mp); + end = start + ptrs;
for (ptr = start; ptr < end; ptr++) { if (*ptr) { - args->blocks += (ptr - start) * factor; + mp->mp_list[hgt] += ptr - start; if (mp->mp_aheight == mp->mp_fheight) return WALK_STOP; - return ptr; /* increase height */ + return WALK_FOLLOW; } } - args->blocks += (end - start) * factor; - return WALK_NEXT; + return WALK_CONTINUE; }
/** @@ -557,12 +583,24 @@ static const __be64 *gfs2_hole_walker(st static int gfs2_hole_size(struct inode *inode, sector_t lblock, u64 len, struct metapath *mp, struct iomap *iomap) { - struct gfs2_hole_walker_args args = { }; - int ret = 0; + struct metapath clone; + u64 hole_size; + int ret; + + clone_metapath(&clone, mp); + ret = gfs2_walk_metadata(inode, &clone, len, gfs2_hole_walker); + if (ret < 0) + goto out; + + if (ret == 1) + hole_size = metapath_to_block(GFS2_SB(inode), &clone) - lblock; + else + hole_size = len; + iomap->length = hole_size << inode->i_blkbits; + ret = 0;
- ret = gfs2_walk_metadata(inode, lblock, len, mp, gfs2_hole_walker, &args); - if (!ret) - iomap->length = args.blocks << inode->i_blkbits; +out: + release_metapath(&clone); return ret; }