xfs: Validate log space at mount time

Validate log space during log mount stage, the underlying function
will drop a warning message via syslog in critical level if the log
space is too small or too large.

[ dchinner: For CRC enable filesystems, abort the mounting of the
filesystem as mkfs should never make a log too small for the given
filesystem configuration. ]

[ dchinner: make a note of the fact that the log size limits in
block counts are in units of filesystem blocks, not basic blocks. ]

Signed-off-by: Jie Liu <jeff.liu@oracle.com>
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Mark Tinguely <tinguely@sgi.com>
Signed-off-by: Ben Myers <bpm@sgi.com>

2 files changed, 49 insertions, 2 deletions

diff --git a/fs/xfs/xfs_fs.h b/fs/xfs/xfs_fs.h
index 74b24b2ecd07..53e33c26f53e 100644
--- a/fs/xfs/xfs_fs.h
+++ b/fs/xfs/xfs_fs.h
@@ -240,7 +240,9 @@ typedef struct xfs_fsop_resblks {
 
 
 /*
- * Minimum and maximum sizes need for growth checks
+ * Minimum and maximum sizes need for growth checks.
+ *
+ * Block counts are in units of filesystem blocks, not basic blocks.
  */
 #define XFS_MIN_AG_BLOCKS       64
 #define XFS_MIN_LOG_BLOCKS      512ULL
diff --git a/fs/xfs/xfs_log.c b/fs/xfs/xfs_log.c
index 704f0959e9c6..b5703ccd533e 100644
--- a/fs/xfs/xfs_log.c
+++ b/fs/xfs/xfs_log.c
@@ -614,7 +614,8 @@ xfs_log_mount(
         xfs_daddr_t     blk_offset,
         int             num_bblks)
 {
-        int             error;
+        int             error = 0;
+        int             min_logfsbs;
 
         if (!(mp->m_flags & XFS_MOUNT_NORECOVERY))
                 xfs_notice(mp, "Mounting Filesystem");
@@ -631,6 +632,50 @@ xfs_log_mount(
         }
 
         /*
+         * Validate the given log space and drop a critical message via syslog
+         * if the log size is too small that would lead to some unexpected
+         * situations in transaction log space reservation stage.
+         *
+         * Note: we can't just reject the mount if the validation fails.  This
+         * would mean that people would have to downgrade their kernel just to
+         * remedy the situation as there is no way to grow the log (short of
+         * black magic surgery with xfs_db).
+         *
+         * We can, however, reject mounts for CRC format filesystems, as the
+         * mkfs binary being used to make the filesystem should never create a
+         * filesystem with a log that is too small.
+         */
+        min_logfsbs = xfs_log_calc_minimum_size(mp);
+
+        if (mp->m_sb.sb_logblocks < min_logfsbs) {
+                xfs_warn(mp,
+                "Log size %d blocks too small, minimum size is %d blocks",
+                         mp->m_sb.sb_logblocks, min_logfsbs);
+                error = EINVAL;
+        } else if (mp->m_sb.sb_logblocks > XFS_MAX_LOG_BLOCKS) {
+                xfs_warn(mp,
+                "Log size %d blocks too large, maximum size is %lld blocks",
+                         mp->m_sb.sb_logblocks, XFS_MAX_LOG_BLOCKS);
+                error = EINVAL;
+        } else if (XFS_FSB_TO_B(mp, mp->m_sb.sb_logblocks) > XFS_MAX_LOG_BYTES) {
+                xfs_warn(mp,
+                "log size %lld bytes too large, maximum size is %lld bytes",
+                         XFS_FSB_TO_B(mp, mp->m_sb.sb_logblocks),
+                         XFS_MAX_LOG_BYTES);
+                error = EINVAL;
+        }
+        if (error) {
+                if (xfs_sb_version_hascrc(&mp->m_sb)) {
+                        xfs_crit(mp, "AAIEEE! Log failed size checks. Abort!");
+                        ASSERT(0);
+                        goto out_free_log;
+                }
+                xfs_crit(mp,
+"Log size out of supported range. Continuing onwards, but if log hangs are\n"
+"experienced then please report this message in the bug report.");
+        }
+
+        /*
          * Initialize the AIL now we have a log.
          */
         error = xfs_trans_ail_init(mp);