After running one too many times into “parent transid verify failed”
that prevents a filesystem from being mounted, I found out how to adjust
some system blocks so that the kernel could get past that check and
mount the filesystem. In one case, I could get all the data I wanted
from the filesystem; in another, many checksums failed and I ended up
throwing it all away, so no guarrantees. mpiechotka''s running into the
problem and bringing it up on IRC prompted me to post for wider
consumption this patch for btrfsck, that will tell you what to do to
make the filesystem mountable again.
Add verbosity to btrfsck so that we can manually recover from a failure
to update the roots.
Signed-off-by: Alexandre Oliva <oliva@lsd.ic.unicamp.br>
---
disk-io.c | 41 +++++++++++++++++++++++++++++++++++++++++
volumes.c | 3 +++
2 files changed, 44 insertions(+), 0 deletions(-)
diff --git a/disk-io.c b/disk-io.c
index a6e1000..6860c26 100644
--- a/disk-io.c
+++ b/disk-io.c
@@ -87,6 +87,22 @@ int csum_tree_block_size(struct extent_buffer *buf, u16
csum_size,
printk("checksum verify failed on %llu wanted %X "
"found %X\n", (unsigned long long)buf->start,
*((int *)result), *((char *)buf->data));
+ if (csum_size == 4) {
+ fprintf(stderr, "dd if=(fd %i) bs=1c skip=%llu count=4 | od -t
x1:\n%02x %02x %02x %02x\n",
+ buf->fd,
+ (unsigned long long)buf->dev_bytenr,
+ (__u8)buf->data[0],
+ (__u8)buf->data[1],
+ (__u8)buf->data[2],
+ (__u8)buf->data[3]);
+ fprintf(stderr, "printf \"\\x%02x\\x%02x\\x%02x\\x%02x\" |
dd of=(fd %i) bs=1c seek=%llu conv=notrunc count=4\n",
+ (__u8)result[0],
+ (__u8)result[1],
+ (__u8)result[2],
+ (__u8)result[3],
+ buf->fd,
+ (unsigned long long)buf->dev_bytenr);
+ }
free(result);
return 1;
}
@@ -165,6 +181,31 @@ static int verify_parent_transid(struct extent_io_tree
*io_tree,
(unsigned long long)eb->start,
(unsigned long long)parent_transid,
(unsigned long long)btrfs_header_generation(eb));
+ fprintf(stderr, "dd if=(fd %i) bs=1c skip=%llu count=8 | od -t x1:\n%02x
%02x %02x %02x %02x %02x %02x %02x\n",
+ eb->fd,
+ (unsigned long long)eb->dev_bytenr
+ + offsetof (struct btrfs_header, generation),
+ (__u8)eb->data[offsetof (struct btrfs_header, generation)],
+ (__u8)eb->data[offsetof (struct btrfs_header, generation) + 1],
+ (__u8)eb->data[offsetof (struct btrfs_header, generation) + 2],
+ (__u8)eb->data[offsetof (struct btrfs_header, generation) + 3],
+ (__u8)eb->data[offsetof (struct btrfs_header, generation) + 4],
+ (__u8)eb->data[offsetof (struct btrfs_header, generation) + 5],
+ (__u8)eb->data[offsetof (struct btrfs_header, generation) + 6],
+ (__u8)eb->data[offsetof (struct btrfs_header, generation) + 7]);
+ btrfs_set_header_generation(eb, parent_transid);
+ fprintf(stderr, "printf
\"\\x%02x\\x%02x\\x%02x\\x%02x\\x%02x\\x%02x\\x%02x\\x%02x\" | dd
of=(fd %i) bs=1c seek=%llu conv=notrunc count=8\n",
+ (__u8)eb->data[offsetof (struct btrfs_header, generation)],
+ (__u8)eb->data[offsetof (struct btrfs_header, generation) + 1],
+ (__u8)eb->data[offsetof (struct btrfs_header, generation) + 2],
+ (__u8)eb->data[offsetof (struct btrfs_header, generation) + 3],
+ (__u8)eb->data[offsetof (struct btrfs_header, generation) + 4],
+ (__u8)eb->data[offsetof (struct btrfs_header, generation) + 5],
+ (__u8)eb->data[offsetof (struct btrfs_header, generation) + 6],
+ (__u8)eb->data[offsetof (struct btrfs_header, generation) + 7],
+ eb->fd,
+ (unsigned long long)eb->dev_bytenr
+ + offsetof (struct btrfs_header, generation));
ret = 1;
out:
clear_extent_buffer_uptodate(io_tree, eb);
diff --git a/volumes.c b/volumes.c
index 7671855..c30a3ba 100644
--- a/volumes.c
+++ b/volumes.c
@@ -188,6 +188,9 @@ int btrfs_open_devices(struct btrfs_fs_devices *fs_devices,
int flags)
device->fd = fd;
if (flags == O_RDWR)
device->writeable = 1;
+ fprintf(stderr, "Device %llu (%s) opened in fd %i\n",
+ (unsigned long long)device->devid,
+ device->name, device->fd);
}
return 0;
fail:
--
1.7.4.4
--
Alexandre Oliva, freedom fighter http://FSFLA.org/~lxoliva/
You must be the change you wish to see in the world. -- Gandhi
Be Free! -- http://FSFLA.org/ FSF Latin America board member
Free Software Evangelist Red Hat Brazil Compiler Engineer
--
To unsubscribe from this list: send the line "unsubscribe linux-btrfs"
in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
