[GFS2] Prevent infinite loop in try_rgrp_unlink()

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>

1 files changed, 17 insertions, 13 deletions

diff --git a/fs/gfs2/rgrp.c b/fs/gfs2/rgrp.c
index ce48c4594ec8..b93ac45b88bb 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);