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Ting-Chang Hou 1fabe43b4e btrfs: send: fix duplicated rmdir operations when using extrefs 
Commit 29d6d30f5c ("Btrfs: send, don't send rmdir for same target
multiple times") has fixed an issue that a send stream contained a rmdir
operation for the same directory multiple times. After that fix we keep
track of the last directory for which we sent a rmdir operation and
compare with it before sending a rmdir for the parent inode of a deleted
hardlink we are processing. But there is still a corner case that in
between rmdir dir operations for the same inode we find deleted hardlinks
for other parent inodes, so tracking just the last inode for which we sent
a rmdir operation is not enough.

Hardlinks of a file in the same directory are stored in the same INODE_REF
item, but if the number of hardlinks is too large and can not fit in a
leaf, we use INODE_EXTREF items to store them. The key of an INODE_EXTREF
item is (inode_id, INODE_EXTREF, hash[name, parent ino]), so between two
hardlinks for the same parent directory, we can find others for other
parent directories. For example for the reproducer below we get the
following (from a btrfs inspect-internal dump-tree output):

    item 0 key (259 INODE_EXTREF 2309449) itemoff 16257 itemsize 26
            index 6925 parent 257 namelen 8 name: foo.6923
    item 1 key (259 INODE_EXTREF 2311350) itemoff 16231 itemsize 26
            index 6588 parent 258 namelen 8 name: foo.6587
    item 2 key (259 INODE_EXTREF 2457395) itemoff 16205 itemsize 26
            index 6611 parent 257 namelen 8 name: foo.6609
    (...)

So tracking the last directory's inode number does not work in this case
since we process a link for parent inode 257, then for 258 and then back
again for 257, and that second time we process a deleted link for 257 we
think we have not yet sent a rmdir operation.

Fix this by using a rbtree to keep track of all the directories for which
we have already sent rmdir operations, and add those directories to the
'check_dirs' ref list in process_recorded_refs() only if the directory is
not yet in the rbtree, otherwise skip it since it means we have already
sent a rmdir operation for that directory.

The following test script reproduces the problem:

  $ cat test.sh
  #!/bin/bash

  DEV=/dev/sdi
  MNT=/mnt/sdi

  mkfs.btrfs -f $DEV
  mount $DEV $MNT

  mkdir $MNT/a $MNT/b

  echo 123 > $MNT/a/foo
  for ((i = 1; i <= 1000; i++)); do
     ln $MNT/a/foo $MNT/a/foo.$i
     ln $MNT/a/foo $MNT/b/foo.$i
  done

  btrfs subvolume snapshot -r $MNT $MNT/snap1
  btrfs send $MNT/snap1 -f /tmp/base.send

  rm -r $MNT/a $MNT/b

  btrfs subvolume snapshot -r $MNT $MNT/snap2
  btrfs send -p $MNT/snap1 $MNT/snap2 -f /tmp/incremental.send

  umount $MNT
  mkfs.btrfs -f $DEV
  mount $DEV $MNT

  btrfs receive $MNT -f /tmp/base.send
  btrfs receive $MNT -f /tmp/incremental.send

  rm -f /tmp/base.send /tmp/incremental.send

  umount $MNT

When running it, it fails like this:

  $ ./test.sh
  (...)
  At subvol snap1
  At snapshot snap2
  ERROR: rmdir o257-9-0 failed: No such file or directory

CC: <stable@vger.kernel.org>
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Ting-Chang Hou <tchou@synology.com>
[ Updated changelog ]
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
 		2025-10-17 18:33:34 +02:00
Documentation sound fixes for 6.17-rc7 2025-09-19 08:22:07 -07:00
LICENSES LICENSES: Replace the obsolete address of the FSF in the GFDL-1.2 2025-07-24 11:15:39 +02:00
arch Fix a SEV-SNP regression when CONFIG_KVM_AMD_SEV is disabled. 2025-09-20 09:27:15 -07:00
block vfs-6.17-rc6.fixes 2025-09-08 07:53:01 -07:00
certs sign-file,extract-cert: use pkcs11 provider for OPENSSL MAJOR >= 3 2024-09-20 19:52:48 +03:00
crypto This push fixes a NULL pointer dereference in ccp and a couple of 2025-09-19 09:58:21 -07:00
drivers Fixes to the Allwinner and Renesas clk drivers: 2025-09-21 11:11:07 -07:00
fs btrfs: send: fix duplicated rmdir operations when using extrefs 2025-10-17 18:33:34 +02:00
include io_uring-6.17-20250919 2025-09-19 12:10:49 -07:00
init 20 hotfixes. 15 are cc:stable and the remainder address post-6.16 issues 2025-09-10 21:19:34 -07:00
io_uring io_uring-6.17-20250919 2025-09-19 12:10:49 -07:00
ipc vfs-6.17-rc1.mmap_prepare 2025-07-28 13:43:25 -07:00
kernel Runtime Verifier fixes for v6.17 2025-09-18 15:22:00 -07:00
lib hardening fixes for v6.17-rc4 2025-08-31 08:56:45 -07:00
mm 15 hotfixes. 11 are cc:stable and the remainder address post-6.16 issues 2025-09-17 21:34:26 -07:00
net Including fixes from wireless. No known regressions at this point. 2025-09-18 10:22:02 -07:00
rust Driver core fixes for 6.17-rc6 2025-09-13 10:36:06 -07:00
samples 15 hotfixes. 11 are cc:stable and the remainder address post-6.16 issues 2025-09-17 21:34:26 -07:00
scripts Rust fixes for v6.17 (2nd) 2025-09-06 12:33:09 -07:00
security + Features 2025-08-04 08:17:28 -07:00
sound ALSA: hda/realtek: Fix mute led for HP Laptop 15-dw4xx 2025-09-18 21:10:05 +02:00
tools LoongArch fixes for v6.17-rc7 2025-09-19 10:06:51 -07:00
usr usr/include: openrisc: don't HDRTEST bpf_perf_event.h 2025-05-12 15:03:17 +09:00
virt Merge tag 'kvm-x86-no_assignment-6.17' of https://github.com/kvm-x86/linux into HEAD 2025-07-29 08:36:42 -04:00
.clang-format Linux 6.15-rc5 2025-05-06 16:39:25 +10:00
.clippy.toml rust: clean Rust 1.88.0's warning about `clippy::disallowed_macros` configuration 2025-05-07 00:11:47 +02:00
.cocciconfig
…
.editorconfig .editorconfig: remove trim_trailing_whitespace option 2024-06-13 16:47:52 +02:00
.get_maintainer.ignore MAINTAINERS: Retire Ralf Baechle 2024-11-12 15:48:59 +01:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore gitignore: allow .pylintrc to be tracked 2025-07-02 17:10:04 -06:00
.mailmap MAINTAINERS: Update Nobuhiro Iwamatsu's email address 2025-09-01 10:36:10 +02:00
.pylintrc docs: add a .pylintrc file with sys path for docs scripts 2025-04-09 12:10:33 -06:00
.rustfmt.toml rust: add `.rustfmt.toml` 2022-09-28 09:02:20 +02:00
COPYING
…
CREDITS MAINTAINERS: retire Boris from TLS maintainers 2025-08-26 17:36:01 -07:00
Kbuild drm: ensure drm headers are self-contained and pass kernel-doc 2025-02-12 10:44:43 +02:00
Kconfig io_uring: Rename KConfig to Kconfig 2025-02-19 14:53:27 -07:00
MAINTAINERS Runtime Verifier fixes for v6.17 2025-09-18 15:22:00 -07:00
Makefile Linux 6.17-rc7 2025-09-21 15:08:52 -07:00
README README: Fix spelling 2024-03-18 03:36:32 -06:00

README 

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.