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xfs: minor odds and ends in xfs_log_recover.c

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Odds and ends in "xfs_log_recover.c".  This patch just contains some
minor things that didn't seem to warrant their own individual
patches:
- In xlog_bread_noalign(), drop an assertion that a pointer is
  non-null (the crash will tell us it was a bad pointer).
- Add a more descriptive header comment for xlog_find_verify_cycle().
- Make a few additions to the comments in xlog_find_head().  Also
  rearrange some expressions in a few spots to produce the same
  result, but in a way that seems more clear what's being computed.

(Updated in response to Dave's review comments.  Note I did not
split this patch like I said I would.)

Signed-off-by: Alex Elder <aelder@sgi.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
This commit is contained in:
Alex Elder 2010-04-15 18:17:34 +00:00
parent e3bb2e30d5
commit 3f943d853d
1 changed files with 15 additions and 16 deletions
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31
fs/xfs/xfs_log_recover.c
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@ -167,7 +167,6 @@ xlog_bread_noalign(
ASSERT(nbblks > 0);
ASSERT(BBTOB(nbblks) <= XFS_BUF_SIZE(bp));
ASSERT(bp);
XFS_BUF_SET_ADDR(bp, log->l_logBBstart + blk_no);
XFS_BUF_READ(bp);
@ -380,14 +379,12 @@ xlog_find_cycle_start(
}
/*
* Check that the range of blocks does not contain the cycle number
* given. The scan needs to occur from front to back and the ptr into the
* region must be updated since a later routine will need to perform another
* test. If the region is completely good, we end up returning the same
* last block number.
*
* Set blkno to -1 if we encounter no errors. This is an invalid block number
* since we don't ever expect logs to get this large.
* Check that a range of blocks does not contain stop_on_cycle_no.
* Fill in *new_blk with the block offset where such a block is
* found, or with -1 (an invalid block number) if there is no such
* block in the range. The scan needs to occur from front to back
* and the pointer into the region must be updated since a later
* routine will need to perform another test.
*/
STATIC int
xlog_find_verify_cycle(
@ -661,7 +658,7 @@ xlog_find_head(
* In this case we want to find the first block with cycle
* number matching last_half_cycle. We expect the log to be
* some variation on
* x + 1 ... | x ...
* x + 1 ... | x ... | x
* The first block with cycle number x (last_half_cycle) will
* be where the new head belongs. First we do a binary search
* for the first occurrence of last_half_cycle. The binary
@ -671,11 +668,13 @@ xlog_find_head(
* the log, then we look for occurrences of last_half_cycle - 1
* at the end of the log. The cases we're looking for look
* like
* x + 1 ... | x | x + 1 | x ...
* ^ binary search stopped here
* v binary search stopped here
* x + 1 ... | x | x + 1 | x ... | x
* ^ but we want to locate this spot
* or
* x + 1 ... | x ... | x - 1 | x
* <---------> less than scan distance
* x + 1 ... | x ... | x - 1 | x
* ^ we want to locate this spot
*/
stop_on_cycle = last_half_cycle;
if ((error = xlog_find_cycle_start(log, bp, first_blk,
@ -731,9 +730,9 @@ xlog_find_head(
* certainly not the head of the log. By searching for
* last_half_cycle-1 we accomplish that.
*/
start_blk = log_bbnum - num_scan_bblks + head_blk;
ASSERT(head_blk <= INT_MAX &&
(xfs_daddr_t) num_scan_bblks - head_blk >= 0);
(xfs_daddr_t) num_scan_bblks >= head_blk);
start_blk = log_bbnum - (num_scan_bblks - head_blk);
if ((error = xlog_find_verify_cycle(log, start_blk,
num_scan_bblks - (int)head_blk,
(stop_on_cycle - 1), &new_blk)))
@ -780,7 +779,7 @@ xlog_find_head(
if ((error = xlog_find_verify_log_record(log, start_blk,
&head_blk, 0)) == -1) {
/* We hit the beginning of the log during our search */
start_blk = log_bbnum - num_scan_bblks + head_blk;
start_blk = log_bbnum - (num_scan_bblks - head_blk);
new_blk = log_bbnum;
ASSERT(start_blk <= INT_MAX &&
(xfs_daddr_t) log_bbnum-start_blk >= 0);