[PATCH 08/51] [GFS2] Prevent infinite loop in try_rgrp_unlink()

swhiteho
2007-10-04T09:20:03Z

From: Bob Peterson <rpeterso@redhat.com>

This is patch three of five for bug #248176.

The try_rgrp_unlink code in rgrp.c had an infinite loop. This was
caused because the bitmap function rgblk_search can return a block
less than the "goal" block, in which case it was looping. The fix is
to make it always march forward as needed.

Signed-off-by: Bob Peterson <rpeterso@redhat.com>
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>

diff --git a/fs/gfs2/rgrp.c b/fs/gfs2/rgrp.c
index ce48c45..b93ac45 100644
--- a/fs/gfs2/rgrp.c
+++ b/fs/gfs2/rgrp.c
@@ -31,6 +31,7 @@
#include "inode.h"

#define BFITNOENT ((u32)~0)
+#define NO_BLOCK ((u64)~0)

/*
* These routines are used by the resource group routines (rgrp.c)
@@ -116,8 +117,7 @@ static unsigned char gfs2_testbit(struct gfs2_rgrpd *rgd, unsigned char *buffer,
* @buffer: the buffer that holds the bitmaps
* @buflen: the length (in bytes) of the buffer
* @goal: start search at this block's bit-pair (within @buffer)
- * @old_state: GFS2_BLKST_XXX the state of the block we're looking for;
- * bit 0 = alloc(1)/free(0), bit 1 = meta(1)/data(0)
+ * @old_state: GFS2_BLKST_XXX the state of the block we're looking for.
*
* Scope of @goal and returned block number is only within this bitmap buffer,
* not entire rgrp or filesystem. @buffer will be offset from the actual
@@ -137,9 +137,13 @@ static u32 gfs2_bitfit(struct gfs2_rgrpd *rgd, unsigned char *buffer,
byte = buffer + (goal / GFS2_NBBY);
bit = (goal % GFS2_NBBY) * GFS2_BIT_SIZE;
end = buffer + buflen;
- alloc = (old_state & 1) ? 0 : 0x55;
+ alloc = (old_state == GFS2_BLKST_FREE) ? 0x55 : 0;

while (byte < end) {
+ /* If we're looking for a free block we can eliminate all
+ bitmap settings with 0x55, which represents four data
+ blocks in a row. If we're looking for a data block, we can
+ eliminate 0x00 which corresponds to four free blocks. */
if ((*byte & 0x55) == alloc) {
blk += (8 - bit) >> 1;

@@ -859,19 +863,21 @@ static int try_rgrp_fit(struct gfs2_rgrpd *rgd, struct gfs2_alloc *al)
static struct inode *try_rgrp_unlink(struct gfs2_rgrpd *rgd, u64 *last_unlinked)
{
struct inode *inode;
- u32 goal = 0;
+ u32 goal = 0, block;
u64 no_addr;

for(;;) {
if (goal >= rgd->rd_data)
break;
- goal = rgblk_search(rgd, goal, GFS2_BLKST_UNLINKED,
- GFS2_BLKST_UNLINKED);
- if (goal == BFITNOENT)
+ block = rgblk_search(rgd, goal, GFS2_BLKST_UNLINKED,
+ GFS2_BLKST_UNLINKED);
+ if (block == BFITNOENT)
break;
- no_addr = goal + rgd->rd_data0;
+ /* rgblk_search can return a block < goal, so we need to
+ keep it marching forward. */
+ no_addr = block + rgd->rd_data0;
goal++;
- if (no_addr < *last_unlinked)
+ if (*last_unlinked != NO_BLOCK && no_addr <= *last_unlinked)
continue;
*last_unlinked = no_addr;
inode = gfs2_inode_lookup(rgd->rd_sbd->sd_vfs, DT_UNKNOWN,
@@ -1152,7 +1158,7 @@ int gfs2_inplace_reserve_i(struct gfs2_inode *ip, char *file, unsigned int line)
struct gfs2_alloc *al = &ip->i_alloc;
struct inode *inode;
int error = 0;
- u64 last_unlinked = 0;
+ u64 last_unlinked = NO_BLOCK;

if (gfs2_assert_warn(sdp, al->al_requested))
return -EINVAL;
@@ -1305,9 +1311,7 @@ static u32 rgblk_search(struct gfs2_rgrpd *rgd, u32 goal,
goal = 0;
}

- if (old_state != new_state) {
- gfs2_assert_withdraw(rgd->rd_sbd, blk != BFITNOENT);
-
+ if (blk != BFITNOENT && old_state != new_state) {
gfs2_trans_add_bh(rgd->rd_gl, bi->bi_bh, 1);
gfs2_setbit(rgd, bi->bi_bh->b_data + bi->bi_offset,
bi->bi_len, blk, new_state);
--
1.5.1.2