xfs: add CRC checks to remote symlinks

Add a header to the remote symlink block, containing location and
owner information, as well as CRCs and LSN fields. This requires
verifiers to be added to the remote symlink buffers for CRC enabled
filesystems.

This also fixes a bug reading multiple block symlinks, where the second
block overwrites the first block when copying out the link name.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Ben Myers <bpm@sgi.com>
Signed-off-by: Ben Myers <bpm@sgi.com>

fs/xfs/xfs_buf_item.h

@@ -49,6 +49,7 @@ extern kmem_zone_t	*xfs_buf_item_zone;
 #define XFS_BLF_AGFL_BUF	(1<<7)
 #define XFS_BLF_AGI_BUF		(1<<8)
 #define XFS_BLF_DINO_BUF	(1<<9)
+#define XFS_BLF_SYMLINK_BUF	(1<<10)
 
 #define XFS_BLF_TYPE_MASK	\
 		(XFS_BLF_UDQUOT_BUF | \
@@ -58,7 +59,8 @@ extern kmem_zone_t	*xfs_buf_item_zone;
 		 XFS_BLF_AGF_BUF | \
 		 XFS_BLF_AGFL_BUF | \
 		 XFS_BLF_AGI_BUF | \
-		 XFS_BLF_DINO_BUF)
+		 XFS_BLF_DINO_BUF | \
+		 XFS_BLF_SYMLINK_BUF)
 
 #define	XFS_BLF_CHUNK		128
 #define	XFS_BLF_SHIFT		7

fs/xfs/xfs_log_recover.c

@@ -45,6 +45,7 @@
 #include "xfs_cksum.h"
 #include "xfs_trace.h"
 #include "xfs_icache.h"
+#include "xfs_symlink.h"
 
 STATIC int
 xlog_find_zeroed(
@@ -2002,6 +2003,14 @@ xlog_recover_do_reg_buffer(
 		}
 		bp->b_ops = &xfs_inode_buf_ops;
 		break;
+	case XFS_BLF_SYMLINK_BUF:
+		if (*(__be32 *)bp->b_addr != cpu_to_be32(XFS_SYMLINK_MAGIC)) {
+			xfs_warn(mp, "Bad symlink block magic!");
+			ASSERT(0);
+			break;
+		}
+		bp->b_ops = &xfs_symlink_buf_ops;
+		break;
 	default:
 		break;
 	}