Re: btrfs and LVM snapshots (Re: kernel BUG at fs/btrfs/extent-tree.c:1772)
On 02/10/2013 01:32 AM, Piotr Pawłow wrote: Hello, Yeah you can't mount images, we clear out the chunk tree so nothing works. Let me know if you run into any problems in the future. Thanks, That's surprising, I haven't seen it mentioned anywhere. With any other filesystem I could use an LVM snapshot to save the original state, but with a multi-device btrfs it would be very risky. Origin and snapshot volumes could easily get mixed up by kernel and tools. I tried that in qemu, and I've seen btrfs happily mount 1 origin and 1 snapshot device as a single FS. And then I've seen it mount both origin devices, even though one of them had old content. Naturally it complained a lot about bad checksums. I can confirm that, even with a single-device btrfs filesystem. However I am curious why you want to use the lvm snapshot capability instead of the btrfs one. Is there any way to avoid such mix-ups? To somehow mark devices so that btrfs would know these devices belong together? Btrfs assume that every device has an unique uuid. However when a device is snapshotted it uuid is copied too, so it is not unique any more. This is the reason of the btrfs confusing. Regards -- To unsubscribe from this list: send the line unsubscribe linux-btrfs in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html -- gpg @keyserver.linux.it: Goffredo Baroncelli (kreijackATinwind.it Key fingerprint BBF5 1610 0B64 DAC6 5F7D 17B2 0EDA 9B37 8B82 E0B5 ss -- To unsubscribe from this list: send the line unsubscribe linux-btrfs in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: Deleted subvolume reappears and other cleaner issues
Thanks for your comments, Josef. Another thing that confuses me is that there are some cases, in which btrfs_drop_snapshot() has a failure, but still returns 0, like for example, if btrfs_del_root() fails. (For cases when btrfs_drop_snapshot() returns non-zero there is a BUG_ON). So in this case for me __btrfs_abort_transaction() sees that trans-blocks_used==0, so it doesn't call __btrfs_std_error, which would further force the filesystem to become RO. So after that btrfs_drop_snapshot successfully completes, and, basically, nobody will retry the subvol deletion. In addition, in this case, after couple of seconds the machine completely freezes for me. I have not yet succeeded to determine why. Thanks, Alex. On Wed, Feb 6, 2013 at 5:14 PM, Josef Bacik jba...@fusionio.com wrote: On Thu, Jan 31, 2013 at 06:03:06AM -0700, Alex Lyakas wrote: Hi, I want to check if any of the below issues are worth/should be fixed: # btrfs_ioctl_snap_destroy() does not commit a transaction. As a result, user can ask to delete a subvol, he receives ok back. Even if user does btrfs sub list, he will not see the deleted subvol (even though the transaction was not committed yet). But if a crash happens, ORPHAN_ITEM will not re-appear after crash. So after crash, the subvolume still exists perfectly fine (happened couple of times here). Same thing happens to normal unlinks, I don't see a reason to have different rules for subvols. # btrfs_drop_snapshot() does not commit a transaction after btrfs_del_orphan_item(). So if the subvol deletion completed in one go (did not have to detach and re-attach to transaction, thus committing the ORPHAN_ITEM and drop_progress/level), then after crash ORPHAN_ITEM will not be in the tree, and subvolume still exists. Again same thing happens with normal files. # btrfs_drop_snapshot() checks btrfs_should_end_transaction(), and then does btrfs_end_transaction_throttle() and btrfs_start_transaction(). However, it looks like it can rejoin the same transaction if transaction was not not blocked yet. Minor issue, perhaps? No if we didn't block then its ok and we wait longer, we only throttle to give the transaction stuff a chance to commit, so if the join logic decides its ok to go on then we're good. # umount may get delayed because of pending-for-deletion subvolumes: btrfs_commit_super() locks the cleaner_mutex, so it will wait for the cleaner to complete. On the other hand, cleaner will not give up until it completes processing all its splice. If currently cleaner is not running, then btrfs_commit_super() calls btrfs_clean_old_snapshots() directly. So does it make sense: - btrfs_commit_super() will not call btrfs_clean_old_snapshots() - close_ctree() calls kthread_stop(cleaner_kthread) early, and cleaner thread periodically checks if it needs to exit I don't quite follow this, but sure? Thanks, Josef -- To unsubscribe from this list: send the line unsubscribe linux-btrfs in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: Diff using send-receive code / RFC
On Sun, Feb 10, 2013 at 10:21:31PM +0530, nafisa mandliwala wrote:
Hello,
We're a team of 4 final year computer science students and are
working on generating a diff between file system snapshots using the
send receive code.
This was just implemented in snapper. Unfortunately I was in a
hurry so the code doesn't look so good. Instead of improving the
code in snapper (C++) I thought about implementing it in C so
that it can be included in btrfsprogs (and libbtrfs).
Here is an example:
# btrfs send -a -p /testsuite/.snapshots/1/snapshot
/testsuite/.snapshots/2/snapshot | cat
At subvol /testsuite/.snapshots/2/snapshot
Comparing testsuite/.snapshots/1/snapshot and testsuite/.snapshots/2/snapshot.
+ /foo
+ /foo/bar
+ /foo/bar/world
Attached you can find my current state. It's completely
unfinished and only works from some test-cases. To get it
compiled you either need some patches posted here earlier
(e.g. NO_FILE_DATA) or must make minor modifications.
But I would like to get feedback about this feature on the list.
Kind Regards,
Arvin
--
Arvin Schnell, aschn...@suse.de
Senior Software Engineer, Research Development
SUSE LINUX Products GmbH, GF: Jeff Hawn, Jennifer Guild, Felix Imendörffer, HRB
16746 (AG Nürnberg)
Maxfeldstraße 5
90409 Nürnberg
Germany
/*
* Copyright (c) 2013 Arvin Schnell aschn...@suse.de
*
* All Rights Reserved.
*
* This program is free software; you can redistribute it and/or modify it
* under the terms of version 2 of the GNU General Public License as published
* by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
* more details.
*
* You should have received a copy of the GNU General Public License along
* with this program; if not, write to the Free Software Foundation, Inc., 59
* Temple Place - Suite 330, Boston, MA 021110-1307, USA.
*/
#define _GNU_SOURCE
#include fcntl.h
#include sys/stat.h
#include string.h
#include dirent.h
#include unistd.h
#include btrfs/send.h
#include btrfs/send-stream.h
#include btrfs/rbtree.h
#include btrfs/send-analyser.h
struct tree_root {
struct rb_root rb_root;
};
struct tree_node {
struct rb_node rb_node;
char *name;
unsigned int status;
struct tree_root children;
};
static void tree_root_init(struct tree_root *root)
{
root-rb_root = RB_ROOT;
}
static struct tree_node *tree_node_init(const char *name)
{
struct tree_node *node = malloc(sizeof(struct tree_node));
node-name = strdup(name);
node-status = 0;
tree_root_init(node-children);
return node;
}
static struct tree_node *tree_find(struct tree_root *root, const char *name)
{
struct rb_node *rb_node = root-rb_root.rb_node;
while (rb_node)
{
struct tree_node *data = rb_entry(rb_node, struct tree_node, rb_node);
int result = strcmp(name, data-name);
if (result 0)
rb_node = rb_node-rb_left;
else if (result 0)
rb_node = rb_node-rb_right;
else
return data;
}
return NULL;
}
static int tree_insert(struct tree_root *root, struct tree_node *node)
{
struct rb_node **new = (root-rb_root.rb_node);
struct rb_node *parent = NULL;
while (*new)
{
struct tree_node *this = rb_entry(*new, struct tree_node, rb_node);
parent = *new;
int result = strcmp(node-name, this-name);
if (result 0)
new = (*new)-rb_left;
else if (result 0)
new = (*new)-rb_right;
else
return 0;
}
rb_link_node(node-rb_node, parent, new);
rb_insert_color(node-rb_node, root-rb_root);
return 1;
}
/* find node or create new one, return 1 if already existing */
static int tree_find_or_insert(struct tree_root *root, const char *name,
struct tree_node **node)
{
struct rb_node **new = (root-rb_root.rb_node);
struct rb_node *parent = NULL;
while (*new)
{
struct tree_node *this = rb_entry(*new, struct tree_node, rb_node);
parent = *new;
int result = strcmp(name, this-name);
if (result 0)
new = (*new)-rb_left;
else if (result 0)
new = (*new)-rb_right;
else
{
*node = this;
return 1;
}
}
*node = tree_node_init(name);
rb_link_node((*node)-rb_node, parent, new);
rb_insert_color((*node)-rb_node, root-rb_root);
return 0;
}
static void tree_remove(struct tree_root *root, struct tree_node *node)
{
rb_erase(node-rb_node, root-rb_root);
free(node-name);
free(node);
}
static void tree_cut(struct tree_root *root, struct tree_node *node)
{
rb_erase(node-rb_node, root-rb_root);
}
static struct tree_node *tree_node_first(struct tree_root *root)
{
struct rb_node *rb_node = rb_first(root-rb_root);
if (!rb_node)
return NULL;
return rb_entry(rb_node, struct tree_node, rb_node);
}
static struct tree_node *tree_node_next(struct tree_node *node)
{
struct rb_node *rb_node = rb_next(node-rb_node);
if (!rb_node)
return NULL;
return rb_entry(rb_node, struct tree_node,
