xfs: nothing special about 1-block log sector

There are a number of places where a log sector size of 1 uses
special case code.  The round_up() and round_down() macros
produce the correct result even when the log sector size is 1, and
this eliminates the need for treating this as a special case.

Signed-off-by: Alex Elder <aelder@sgi.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>

1 files changed, 29 insertions, 13 deletions

diff --git a/fs/xfs/xfs_log_recover.c b/fs/xfs/xfs_log_recover.c
index b5eab63eb12d..629e88b38bd1 100644
--- a/fs/xfs/xfs_log_recover.c
+++ b/fs/xfs/xfs_log_recover.c
@@ -77,6 +77,11 @@ xlog_buf_bbcount_valid(
         return bbcount > 0 && bbcount <= log->l_logBBsize;
 }
 
+/*
+ * Allocate a buffer to hold log data.  The buffer needs to be able
+ * to map to a range of nbblks basic blocks at any valid (basic
+ * block) offset within the log.
+ */
 STATIC xfs_buf_t *
 xlog_get_bp(
         xlog_t          *log,
@@ -89,11 +94,26 @@ xlog_get_bp(
                 return NULL;
         }
 
-        if (log->l_sectbb_log) {
-                if (nbblks > 1)
-                        nbblks += xlog_sectbb(log);
-                nbblks = round_up(nbblks, xlog_sectbb(log));
-        }
+        /*
+         * We do log I/O in units of log sectors (a power-of-2
+         * multiple of the basic block size), so we round up the
+         * requested size to acommodate the basic blocks required
+         * for complete log sectors.
+         *
+         * In addition, the buffer may be used for a non-sector-
+         * aligned block offset, in which case an I/O of the
+         * requested size could extend beyond the end of the
+         * buffer.  If the requested size is only 1 basic block it
+         * will never straddle a sector boundary, so this won't be
+         * an issue.  Nor will this be a problem if the log I/O is
+         * done in basic blocks (sector size 1).  But otherwise we
+         * extend the buffer by one extra log sector to ensure
+         * there's space to accomodate this possiblility.
+         */
+        if (nbblks > 1 && log->l_sectbb_log)
+                nbblks += xlog_sectbb(log);
+        nbblks = round_up(nbblks, xlog_sectbb(log));
+
         return xfs_buf_get_noaddr(BBTOB(nbblks), log->l_mp->m_logdev_targp);
 }
 
@@ -142,10 +162,8 @@ xlog_bread_noalign(
                 return EFSCORRUPTED;
         }
 
-        if (log->l_sectbb_log) {
-                blk_no = round_down(blk_no, xlog_sectbb(log));
-                nbblks = round_up(nbblks, xlog_sectbb(log));
-        }
+        blk_no = round_down(blk_no, xlog_sectbb(log));
+        nbblks = round_up(nbblks, xlog_sectbb(log));
 
         ASSERT(nbblks > 0);
         ASSERT(BBTOB(nbblks) <= XFS_BUF_SIZE(bp));
@@ -204,10 +222,8 @@ xlog_bwrite(
                 return EFSCORRUPTED;
         }
 
-        if (log->l_sectbb_log) {
-                blk_no = round_down(blk_no, xlog_sectbb(log));
-                nbblks = round_up(nbblks, xlog_sectbb(log));
-        }
+        blk_no = round_down(blk_no, xlog_sectbb(log));
+        nbblks = round_up(nbblks, xlog_sectbb(log));
 
         ASSERT(nbblks > 0);
         ASSERT(BBTOB(nbblks) <= XFS_BUF_SIZE(bp));