http://bugzilla.suse.com/show_bug.cgi?id=1025048
Bug ID: 1025048
Summary: Btrfs: incremental send, don't delay directory renames
unnecessarily
Classification: openSUSE
Product: openSUSE Distribution
Version: Leap 42.1
Hardware: Other
OS: Other
Status: NEW
Severity: Normal
Priority: P5 - None
Component: Kernel
Assignee: jeffm@suse.com
Reporter: jeffm@suse.com
QA Contact: qa-bugs@suse.de
Found By: ---
Blocker: ---
From: Filipe Manana
Date: Fri, 27 Mar 2015 17:50:45 +0000
Subject: Btrfs: incremental send, don't delay directory renames unnecessarily
Git-commit: 80aa6027561eef12b49031d46fd6724daf1e7fb6
Patch-mainline: v4.2-rc2
References: revisit
Even though we delay the rename of directories when they become
descendents of other directories that were also renamed in the send
root to prevent infinite path build loops, we were doing it in cases
where this was not needed and was actually harmful resulting in
infinite path build loops as we ended up with a circular dependency
of delayed directory renames.
Consider the following reproducer:
$ mkfs.btrfs -f /dev/sdb
$ mount /dev/sdb /mnt
$ mkfs.btrfs -f /dev/sdc
$ mount /dev/sdc /mnt2
$ mkdir /mnt/data
$ mkdir /mnt/data/n1
$ mkdir /mnt/data/n1/n2
$ mkdir /mnt/data/n4
$ mkdir /mnt/data/n1/n2/p1
$ mkdir /mnt/data/n1/n2/p1/p2
$ mkdir /mnt/data/t6
$ mkdir /mnt/data/t7
$ mkdir -p /mnt/data/t5/t7
$ mkdir /mnt/data/t2
$ mkdir /mnt/data/t4
$ mkdir -p /mnt/data/t1/t3
$ mkdir /mnt/data/p1
$ mv /mnt/data/t1 /mnt/data/p1
$ mkdir -p /mnt/data/p1/p2
$ mv /mnt/data/t4 /mnt/data/p1/p2/t1
$ mv /mnt/data/t5 /mnt/data/n4/t5
$ mv /mnt/data/n1/n2/p1/p2 /mnt/data/n4/t5/p2
$ mv /mnt/data/t7 /mnt/data/n4/t5/p2/t7
$ mv /mnt/data/t2 /mnt/data/n4/t1
$ mv /mnt/data/p1 /mnt/data/n4/t5/p2/p1
$ mv /mnt/data/n1/n2 /mnt/data/n4/t5/p2/p1/p2/n2
$ mv /mnt/data/n4/t5/p2/p1/p2/t1 /mnt/data/n4/t5/p2/p1/p2/n2/t1
$ mv /mnt/data/n4/t5/t7 /mnt/data/n4/t5/p2/p1/p2/n2/t1/t7
$ mv /mnt/data/n4/t5/p2/p1/t1/t3 /mnt/data/n4/t5/p2/p1/p2/n2/t1/t3
$ mv /mnt/data/n4/t5/p2/p1/p2/n2/p1 /mnt/data/n4/t5/p2/p1/p2/n2/t1/t7/p1
$ mv /mnt/data/t6 /mnt/data/n4/t5/p2/p1/p2/n2/t1/t3/t5
$ mv /mnt/data/n4/t5/p2/p1/t1 /mnt/data/n4/t5/p2/p1/p2/n2/t1/t3/t1
$ mv /mnt/data/n1 /mnt/data/n4/t5/p2/p1/p2/n2/t1/t7/p1/n1
$ btrfs subvolume snapshot -r /mnt /mnt/snap1
$ mv /mnt/data/n4/t1 /mnt/data/n4/t5/p2/p1/p2/n2/t1/t7/p1/t1
$ mv /mnt/data/n4/t5/p2/p1/p2/n2/t1 /mnt/data/n4/
$ mv /mnt/data/n4/t5/p2/p1/p2/n2 /mnt/data/n4/t1/n2
$ mv /mnt/data/n4/t1/t7/p1 /mnt/data/n4/t1/n2/p1
$ mv /mnt/data/n4/t1/t3/t1 /mnt/data/n4/t1/n2/t1
$ mv /mnt/data/n4/t1/t3 /mnt/data/n4/t1/n2/t1/t3
$ mv /mnt/data/n4/t5/p2/p1/p2 /mnt/data/n4/t1/n2/p1/p2
$ mv /mnt/data/n4/t1/t7 /mnt/data/n4/t1/n2/p1/t7
$ mv /mnt/data/n4/t5/p2/p1 /mnt/data/n4/t1/n2/p1/p2/p1
$ mv /mnt/data/n4/t1/n2/t1/t3/t5 /mnt/data/n4/t1/n2/p1/p2/t5
$ mv /mnt/data/n4/t5 /mnt/data/n4/t1/n2/p1/p2/p1/t5
$ mv /mnt/data/n4/t1/n2/p1/p2/p1/t5/p2 /mnt/data/n4/t1/n2/p1/p2/p1/p2
$ mv /mnt/data/n4/t1/n2/p1/p2/p1/p2/t7 /mnt/data/n4/t1/t7
$ btrfs subvolume snapshot -r /mnt /mnt/snap2
$ btrfs send /mnt/snap1 | btrfs receive /mnt2
$ btrfs send -p /mnt/snap1 /mnt/snap2 | btrfs receive -vv /mnt2
ERROR: send ioctl failed with -12: Cannot allocate memory
This reproducer resulted in an infinite path build loop when building the
path for inode 266 because the following circular dependency of delayed
directory renames was created:
ino 272 <- ino 261 <- ino 259 <- ino 268 <- ino 267 <- ino 261
Where the notation "X <- Y" means the rename of inode X is delayed by the
rename of inode Y (X will be renamed after Y is renamed). This resulted
in an infinite path build loop of inode 266 because that inode has inode
261 as an ancestor in the send root and inode 261 is in the circular
dependency of delayed renames listed above.
Fix this by not delaying the rename of a directory inode if an ancestor of
the inode in the send root, which has a delayed rename operation, is not
also a descendent of the inode in the parent root.
Thanks to Robbie Ko for sending the reproducer example.
A test case for xfstests follows soon.
Reported-by: Robbie Ko
Signed-off-by: Filipe Manana
Acked-by: Jeff Mahoney
---
fs/btrfs/send.c | 48 ++++++++++++++++++++++++++++++++++++++++++++++--
1 file changed, 46 insertions(+), 2 deletions(-)
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