[PATCH 11/8] xfs_logprint: fix continuation transactions

[Dave Chinner <david@xxxxxxxxxxxxx>]

From: Dave Chinner <dchinner@xxxxxxxxxx>

As demonstrated by xfs/295, continuation transactions cause of
problems for xfs_logprint. The failure demonstrated by the test is
that the buffer log format structures are variable sized on disk -
the dirty bitmap is sized according to the buffer length, not fixed
to the length of the maximum supported buffer size.

xfs_logprint assumes that the buf log format reocrds are of fixed
size, and so when a short buffer is found it fails to handle it
properly and treats it like a continuation record.  This causses the
opheader pointer to be incremented incorrectly and then logprint
wanders off into a dark corner and gets eaten by a grue.

While fixing this, make the xlog_print_record code that does the
transaction opheader walking a little easier to read and stop it
from outputting binary data direct to the console by converting the
no-data-print case to use a hex dumping loop.

Signed-off-by: Dave Chinner <dchinner@xxxxxxxxxx>
---
 logprint/log_misc.c |   22 +++++++++++++++++-----
 1 file changed, 17 insertions(+), 5 deletions(-)

diff --git a/logprint/log_misc.c b/logprint/log_misc.c
index 30b7ea6..d08f900 100644
--- a/logprint/log_misc.c
+++ b/logprint/log_misc.c
@@ -268,7 +268,13 @@ xlog_print_trans_buffer(xfs_caddr_t *ptr, int len, int *i, 
int num_ops)
     blen = f->blf_len;
     map_size = f->blf_map_size;
     flags = f->blf_flags;
-    struct_size = sizeof(xfs_buf_log_format_t);
+
+    /*
+     * size of the format header is dependent on the size of the bitmap, not
+     * the size of the in-memory structure. Hence the slightly obtuse
+     * calculation.
+     */
+    struct_size = offsetof(struct xfs_buf_log_format, blf_map_size) + map_size;
 
     if (len >= struct_size) {
        ASSERT((len - sizeof(struct_size)) % sizeof(int) == 0);
@@ -933,22 +939,28 @@ xlog_print_record(int                       fd,
        continued = ((op_head->oh_flags & XLOG_WAS_CONT_TRANS) ||
                     (op_head->oh_flags & XLOG_CONTINUE_TRANS));
 
-       /* print transaction data */
-       if (print_no_data ||
-           (continued && be32_to_cpu(op_head->oh_len) == 0)) {
+       if (continued && be32_to_cpu(op_head->oh_len) == 0)
+               continue;
+
+       if (print_no_data) {
            for (n = 0; n < be32_to_cpu(op_head->oh_len); n++) {
-               printf("%c", *ptr);
+               printf("0x%02x ", (unsigned int)*ptr);
+               if (n % 16 == 15)
+                       printf("\n");
                ptr++;
            }
            printf("\n");
            continue;
        }
+
+       /* print transaction data */
        if (xlog_print_find_tid(be32_to_cpu(op_head->oh_tid),
                                op_head->oh_flags & XLOG_WAS_CONT_TRANS)) {
            printf(_("Left over region from split log item\n"));
            ptr += be32_to_cpu(op_head->oh_len);
            continue;
        }
+
        if (be32_to_cpu(op_head->oh_len) != 0) {
            if (*(uint *)ptr == XFS_TRANS_HEADER_MAGIC) {
                skip = xlog_print_trans_header(&ptr,