hammer - Add tunable vfs.hammer.skip_redo

This tunable can be used to change the behaviour of the redo
recovery in the case a HAMMER filesystem is not able to mount.

Following values are accepted:

	0 - Run redo recovery normally and fail to mount if
	    the operation fails (default).
	1 - Run redo recovery, but don't fail to mount if the
	    operation fails.
	2 - Completely skip redo recovery (only for severe error
	    conditions and/or debugging).

Pointed-out-by: dillon

diff --git a/share/man/man5/hammer.5 b/share/man/man5/hammer.5
index 1f79973..f6e076c 100644 (file)
--- a/share/man/man5/hammer.5
+++ b/share/man/man5/hammer.5
@@ -29,7 +29,7 @@
 .\" OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 .\" SUCH DAMAGE.
 .\"
-.Dd April 19, 2011
+.Dd August 14, 2012
 .Dt HAMMER 5
 .Os
 .Sh NAME
@@ -103,6 +103,24 @@ After a non-graceful system shutdown,
 file systems will be brought back into a fully coherent state
 when mounting the file system, usually within a few seconds.
 .Pp
+In the unlikely case
+.Nm
+mount fails due redo recovery (stage 2 recovery) being corrupted, a
+workaround to skip this stage can be applied by setting the following tunable:
+.Bd -literal -offset indent
+vfs.hammer.skip_redo=<value>
+.Ed
+.Pp
+Possible values are:
+.Bl -tag -width indent
+.It 0
+Run redo recovery normally and fail to mount in the case of error (default).
+.It 1
+Run redo recovery but continue mounting if an error appears.
+.It 2
+Completely bypass redo recovery.
+.El
+.Pp
 Related commands:
 .Xr mount_hammer 8
 .Ss Large File Systems & Multi Volume

diff --git a/sys/vfs/hammer/hammer.h b/sys/vfs/hammer/hammer.h
index f837a07..745d5f5 100644 (file)
--- a/sys/vfs/hammer/hammer.h
+++ b/sys/vfs/hammer/hammer.h
@@ -998,6 +998,7 @@ extern struct vop_ops hammer_spec_vops;
 extern struct vop_ops hammer_fifo_vops;
 extern struct bio_ops hammer_bioops;
 
+extern int hammer_skip_redo;
 extern int hammer_debug_io;
 extern int hammer_debug_general;
 extern int hammer_debug_debug;

diff --git a/sys/vfs/hammer/hammer_recover.c b/sys/vfs/hammer/hammer_recover.c
index 0b699d2..d7566ca 100644 (file)
--- a/sys/vfs/hammer/hammer_recover.c
+++ b/sys/vfs/hammer/hammer_recover.c
@@ -116,6 +116,21 @@
 #include "hammer.h"
 
 /*
+ * Specify the way we want to handle stage2 errors.
+ *
+ * Following values are accepted:
+ *
+ * 0 - Run redo recovery normally and fail to mount if
+ *     the operation fails (default).
+ * 1 - Run redo recovery, but don't fail to mount if the
+ *     operation fails.
+ * 2 - Completely skip redo recovery (only for severe error
+ *     conditions and/or debugging.
+ */
+int hammer_skip_redo = 0;
+TUNABLE_INT("vfs.hammer.skip_redo", &hammer_skip_redo);
+
+/*
  * Each rterm entry has a list of fifo offsets indicating termination
  * points.  These are stripped as the scan progresses.
  */
@@ -529,6 +544,16 @@ hammer_recover_stage2(hammer_mount_t hmp, hammer_volume_t root_volume)
        KKASSERT(hmp->ronly == 0);
        RB_INIT(&rterm_root);
 
+       if (hammer_skip_redo == 1)
+               kprintf("HAMMER(%s) recovery redo marked as optional\n",
+                   root_volume->ondisk->vol_name);
+
+       if (hammer_skip_redo == 2) {
+               kprintf("HAMMER(%s) recovery redo skipped.\n",
+                   root_volume->ondisk->vol_name);
+               return (0);
+       }
+
        /*
         * Examine the UNDO FIFO.  If it is empty the filesystem is clean
         * and no action need be taken.
@@ -741,7 +766,13 @@ fatal:
                kprintf("HAMMER(%s) End redo recovery\n",
                        root_volume->ondisk->vol_name);
        }
-       return (error);
+
+       if (error && hammer_skip_redo == 1)
+               kprintf("HAMMER(%s) recovery redo error %d, "
+                   " skipping.\n", root_volume->ondisk->vol_name,
+                   error);
+
+       return (hammer_skip_redo ? 0 : error);
 }
 
 /*