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[PATCH v2] logprint: Fix printing of AGF and AGI buffers

To: xfs@xxxxxxxxxxx
Subject: [PATCH v2] logprint: Fix printing of AGF and AGI buffers
From: Jan Kara <jack@xxxxxxx>
Date: Wed, 16 Jul 2014 22:45:21 +0200
Cc: Christoph Hellwig <hch@xxxxxxxxxxxxx>, dchinner@xxxxxxxxxx, Jan Kara <jack@xxxxxxx>
Delivered-to: xfs@xxxxxxxxxxx
Currently xfs_logprint doesn't show detailed data about AGF and AGI
buffers and instead always shows "Out of space". This is because
xfs_agf_t has additional fields and padding which we never read from
disk and thus buffer length is always smaller than the size of
xfs_agf_t or xfs_agi_t respectively.

Fix the problem by only making sure we have enough data in the buffer
to contain all the information we want to print.

Signed-off-by: Jan Kara <jack@xxxxxxx>
---
 logprint/log_misc.c | 20 ++++++++++++++++++--
 1 file changed, 18 insertions(+), 2 deletions(-)

diff --git a/logprint/log_misc.c b/logprint/log_misc.c
index d482cf3fba57..c9286c67b913 100644
--- a/logprint/log_misc.c
+++ b/logprint/log_misc.c
@@ -325,7 +325,15 @@ xlog_print_trans_buffer(xfs_caddr_t *ptr, int len, int *i, 
int num_ops)
        } else if (be32_to_cpu(*(__be32 *)(*ptr)) == XFS_AGI_MAGIC) {
                agi = (xfs_agi_t *)(*ptr);
                printf(_("AGI Buffer: XAGI  "));
-               if (be32_to_cpu(head->oh_len) < sizeof(xfs_agi_t) -
+               /*
+                * v4 filesystems only contain the fields before the uuid.
+                * Even v5 filesystems don't log any field beneath it. That
+                * means that the size that is logged is almost always going to
+                * be smaller than the structure itself. Hence we need to make
+                * sure that the buffer contains all the data we want to print
+                * rather than just check against the structure size.
+                */
+               if (be32_to_cpu(head->oh_len) < offsetof(xfs_agi_t, agi_uuid) -
                                XFS_AGI_UNLINKED_BUCKETS*sizeof(xfs_agino_t)) {
                        printf(_("out of space\n"));
                } else {
@@ -367,7 +375,15 @@ xlog_print_trans_buffer(xfs_caddr_t *ptr, int len, int *i, 
int num_ops)
        } else if (be32_to_cpu(*(__be32 *)(*ptr)) == XFS_AGF_MAGIC) {
                agf = (xfs_agf_t *)(*ptr);
                printf(_("AGF Buffer: XAGF  "));
-               if (be32_to_cpu(head->oh_len) < sizeof(xfs_agf_t)) {
+               /*
+                * v4 filesystems only contain the fields before the uuid.
+                * Even v5 filesystems don't log any field beneath it. That
+                * means that the size that is logged is almost always going to
+                * be smaller than the structure itself. Hence we need to make
+                * sure that the buffer contains all the data we want to print
+                * rather than just check against the structure size.
+                */
+               if (be32_to_cpu(head->oh_len) < offsetof(xfs_agf_t, agf_uuid)) {
                        printf(_("Out of space\n"));
                } else {
                        printf("\n");
-- 
1.8.1.4

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