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Filipe Manana e867056462 Btrfs: fix missing hole after hole punching and fsync when using NO_HOLES 
commit 0e56315ca1 upstream.

When using the NO_HOLES feature, if we punch a hole into a file and then
fsync it, there are cases where a subsequent fsync will miss the fact that
a hole was punched, resulting in the holes not existing after replaying
the log tree.

Essentially these cases all imply that, tree-log.c:copy_items(), is not
invoked for the leafs that delimit holes, because nothing changed those
leafs in the current transaction. And it's precisely copy_items() where
we currenly detect and log holes, which works as long as the holes are
between file extent items in the input leaf or between the beginning of
input leaf and the previous leaf or between the last item in the leaf
and the next leaf.

First example where we miss a hole:

  *) The extent items of the inode span multiple leafs;

  *) The punched hole covers a range that affects only the extent items of
     the first leaf;

  *) The fsync operation is done in full mode (BTRFS_INODE_NEEDS_FULL_SYNC
     is set in the inode's runtime flags).

  That results in the hole not existing after replaying the log tree.

  For example, if the fs/subvolume tree has the following layout for a
  particular inode:

      Leaf N, generation 10:

      [ ... INODE_ITEM INODE_REF EXTENT_ITEM (0 64K) EXTENT_ITEM (64K 128K) ]

      Leaf N + 1, generation 10:

      [ EXTENT_ITEM (128K 64K) ... ]

  If at transaction 11 we punch a hole coverting the range [0, 128K[, we end
  up dropping the two extent items from leaf N, but we don't touch the other
  leaf, so we end up in the following state:

      Leaf N, generation 11:

      [ ... INODE_ITEM INODE_REF ]

      Leaf N + 1, generation 10:

      [ EXTENT_ITEM (128K 64K) ... ]

  A full fsync after punching the hole will only process leaf N because it
  was modified in the current transaction, but not leaf N + 1, since it
  was not modified in the current transaction (generation 10 and not 11).
  As a result the fsync will not log any holes, because it didn't process
  any leaf with extent items.

Second example where we will miss a hole:

  *) An inode as its items spanning 5 (or more) leafs;

  *) A hole is punched and it covers only the extents items of the 3rd
     leaf. This resulsts in deleting the entire leaf and not touching any
     of the other leafs.

  So the only leaf that is modified in the current transaction, when
  punching the hole, is the first leaf, which contains the inode item.
  During the full fsync, the only leaf that is passed to copy_items()
  is that first leaf, and that's not enough for the hole detection
  code in copy_items() to determine there's a hole between the last
  file extent item in the 2nd leaf and the first file extent item in
  the 3rd leaf (which was the 4th leaf before punching the hole).

Fix this by scanning all leafs and punch holes as necessary when doing a
full fsync (less common than a non-full fsync) when the NO_HOLES feature
is enabled. The lack of explicit file extent items to mark holes makes it
necessary to scan existing extents to determine if holes exist.

A test case for fstests follows soon.

Fixes: 16e7549f04 ("Btrfs: incompatible format change to remove hole extents")
CC: stable@vger.kernel.org # 4.4+
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
History 2020-02-11 04:37:03 -08:00
arch powerpc/futex: Fix incorrect user access blocking 2020-02-11 04:37:02 -08:00
block block: allow partitions on host aware zone devices 2020-01-26 09:59:08 -07:00
certs certs: Add wrapper function to check blacklisted binary hash 2019-11-12 12:25:50 +11:00
crypto crypto: api - Fix race condition in crypto_spawn_alg 2020-02-11 04:37:01 -08:00
Documentation PM / devfreq: Add new name attribute for sysfs 2020-02-04 18:18:01 +00:00
drivers scsi: qla2xxx: Fix unbound NVME response length 2020-02-11 04:37:02 -08:00
fs Btrfs: fix missing hole after hole punching and fsync when using NO_HOLES 2020-02-11 04:37:03 -08:00
include crypto: pcrypt - Avoid deadlock by using per-instance padata queues 2020-02-11 04:36:58 -08:00
init Revert "um: Enable CONFIG_CONSTRUCTORS" 2020-02-01 09:33:00 +00:00
ipc ipc/msg.c: consolidate all xxxctl_down() functions 2020-02-11 04:36:39 -08:00
kernel bpf, devmap: Pass lockdep expression to RCU lists 2020-02-11 04:36:59 -08:00
lib lib/test_kasan.c: fix memory leak in kmalloc_oob_krealloc_more() 2020-02-11 04:36:45 -08:00
LICENSES LICENSES: Rename other to deprecated 2019-05-03 06:34:32 -06:00
mm mm: move_pages: report the number of non-attempted pages 2020-02-11 04:36:44 -08:00
net flow_dissector: Fix to use new variables for port ranges in bpf hook 2020-02-11 04:36:59 -08:00
samples samples/bpf: Reintroduce missed build targets 2020-02-11 04:37:00 -08:00
scripts scripts/find-unused-docs: Fix massive false positives 2020-02-11 04:36:53 -08:00
security tomoyo: Use atomic_t for statistics counter 2020-02-04 18:18:02 +00:00
sound ASoC: SOF: core: release resources on errors in probe_continue 2020-02-11 04:36:57 -08:00
tools selftests: bpf: Ignore FIN packets for reuseport tests 2020-02-11 04:37:00 -08:00
usr gen_initramfs_list.sh: fix 'bad variable name' error 2020-01-04 00:00:48 +09:00
virt KVM: arm64: Only sign-extend MMIO up to register width 2020-02-11 04:36:47 -08:00
.clang-format clang-format: Update with the latest for_each macro list 2019-08-31 10:00:51 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore Opt out of scripts/get_maintainer.pl 2019-05-16 10:53:40 -07:00
.gitattributes .gitattributes: use 'dts' diff driver for dts files 2019-12-04 19:44:11 -08:00
.gitignore modpost: dump missing namespaces into a single modules.nsdeps file 2019-11-11 20:10:01 +09:00
.mailmap MAINTAINERS: update my email address 2020-01-11 14:33:39 -08:00
COPYING COPYING: use the new text with points to the license files 2018-03-23 12:41:45 -06:00
CREDITS Linux 5.4-rc4 2019-10-29 04:43:29 -06:00
Kbuild kbuild: do not descend to ./Kbuild when cleaning 2019-08-21 21:03:58 +09:00
Kconfig docs: kbuild: convert docs to ReST and rename to *.rst 2019-06-14 14:21:21 -06:00
MAINTAINERS MAINTAINERS: correct entries for ISDN/mISDN section 2020-02-11 04:36:38 -08:00
Makefile Linux 5.5.2 2020-02-04 18:18:03 +00:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -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 Restructured Text 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.