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Filipe Manana e6e3dec6c3 btrfs: update generation of hole file extent item when merging holes 
When punching a hole into a file range that is adjacent with a hole and we
are not using the no-holes feature, we expand the range of the adjacent
file extent item that represents a hole, to save metadata space.

However we don't update the generation of hole file extent item, which
means a full fsync will not log that file extent item if the fsync happens
in a later transaction (since commit 7f30c07288 ("btrfs: stop copying
old file extents when doing a full fsync")).

For example, if we do this:

    $ mkfs.btrfs -f -O ^no-holes /dev/sdb
    $ mount /dev/sdb /mnt
    $ xfs_io -f -c "pwrite -S 0xab 2M 2M" /mnt/foobar
    $ sync

We end up with 2 file extent items in our file:

1) One that represents the hole for the file range [0, 2M), with a
   generation of 7;

2) Another one that represents an extent covering the range [2M, 4M).

After that if we do the following:

    $ xfs_io -c "fpunch 2M 2M" /mnt/foobar

We end up with a single file extent item in the file, which represents a
hole for the range [0, 4M) and with a generation of 7 - because we end
dropping the data extent for range [2M, 4M) and then update the file
extent item that represented the hole at [0, 2M), by increasing
length from 2M to 4M.

Then doing a full fsync and power failing:

    $ xfs_io -c "fsync" /mnt/foobar
    <power failure>

will result in the full fsync not logging the file extent item that
represents the hole for the range [0, 4M), because its generation is 7,
which is lower than the generation of the current transaction (8).
As a consequence, after mounting again the filesystem (after log replay),
the region [2M, 4M) does not have a hole, it still points to the
previous data extent.

So fix this by always updating the generation of existing file extent
items representing holes when we merge/expand them. This solves the
problem and it's the same approach as when we merge prealloc extents that
got written (at btrfs_mark_extent_written()). Setting the generation to
the current transaction's generation is also what we do when merging
the new hole extent map with the previous one or the next one.

A test case for fstests, covering both cases of hole file extent item
merging (to the left and to the right), will be sent soon.

Fixes: 7f30c07288 ("btrfs: stop copying old file extents when doing a full fsync")
CC: stable@vger.kernel.org # 5.18+
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2022-08-22 18:06:42 +02:00
arch highmem: Make __kunmap_{local,atomic}() take const void pointer 2022-07-25 17:45:40 +02:00
block block: fix missing blkcg_bio_issue_init 2022-07-14 10:54:49 -06:00
certs certs: make system keyring depend on x509 parser 2022-07-24 12:53:55 -07:00
crypto crypto: s390 - do not depend on CRYPTO_HW for SIMD implementations 2022-07-06 20:04:06 -07:00
Documentation * Check for invalid flags to KVM_CAP_X86_USER_SPACE_MSR 2022-07-23 10:22:26 -07:00
drivers - Make retbleed mitigations 64-bit only (32-bit will need a bit more 2022-07-24 09:40:17 -07:00
fs btrfs: update generation of hole file extent item when merging holes 2022-08-22 18:06:42 +02:00
include block: add bdev_max_segments() helper 2022-07-25 17:45:41 +02:00
init gcc-12: disable '-Warray-bounds' universally for now 2022-06-09 10:11:12 -07:00
ipc ipc: Free mq_sysctls if ipc namespace creation failed 2022-06-22 17:47:41 -05:00
kernel A single fix to correct a wrong BUG_ON() condition for deboosted tasks. 2022-07-24 09:50:53 -07:00
lib ubsan: disable UBSAN_DIV_ZERO for clang 2022-07-14 15:45:26 -07:00
LICENSES LICENSES/LGPL-2.1: Add LGPL-2.1-or-later as valid identifiers 2021-12-16 14:33:10 +01:00
mm highmem: Make __kunmap_{local,atomic}() take const void pointer 2022-07-25 17:45:40 +02:00
net net/sched: cls_api: Fix flow action initialization 2022-07-20 10:54:27 +01:00
samples Fixes and minor clean ups for tracing: 2022-07-12 16:17:40 -07:00
scripts scripts/gdb: Fix gdb 'lx-symbols' command 2022-07-21 10:40:55 -07:00
security lockdown: Fix kexec lockdown bypass with ima policy 2022-07-20 09:56:48 -07:00
sound ASoC: Drop Rockchip BCLK management for v5.19 2022-07-15 12:31:07 +02:00
tools * Check for invalid flags to KVM_CAP_X86_USER_SPACE_MSR 2022-07-23 10:22:26 -07:00
usr Not a lot of material this cycle. Many singleton patches against various 2022-05-27 11:22:03 -07:00
virt KVM: x86: disable preemption around the call to kvm_arch_vcpu_{un|}blocking 2022-06-09 10:52:20 -04:00
.clang-format clang-format: Fix space after for_each macros 2022-05-20 19:27:16 +02:00
.cocciconfig
.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 kbuild: split the second line of *.mod into *.usyms 2022-05-08 03:16:59 +09:00
.mailmap cxl fixes for 5.19-rc6 2022-07-08 12:55:25 -07:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: mark ARM/PALM TREO SUPPORT orphan 2022-07-07 15:17:00 +02:00
Kbuild kbuild: rename hostprogs-y/always to hostprogs/always-y 2020-02-04 01:53:07 +09:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS Pin control fixes for the v5.19 kernel cycle: 2022-07-22 12:24:04 -07:00
Makefile Linux 5.19-rc8 2022-07-24 13:26:27 -07:00
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.