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Filipe Manana f803185361 Btrfs: send, skip backreference walking for extents with many references
commit fd0ddbe250 upstream.

Backreference walking, which is used by send to figure if it can issue
clone operations instead of write operations, can be very slow and use
too much memory when extents have many references. This change simply
skips backreference walking when an extent has more than 64 references,
in which case we fallback to a write operation instead of a clone
operation. This limit is conservative and in practice I observed no
signicant slowdown with up to 100 references and still low memory usage
up to that limit.

This is a temporary workaround until there are speedups in the backref
walking code, and as such it does not attempt to add extra interfaces or
knobs to tweak the threshold.

Reported-by: Atemu <atemu.main@gmail.com>
Link: https://lore.kernel.org/linux-btrfs/CAE4GHgkvqVADtS4AzcQJxo0Q1jKQgKaW3JGp3SGdoinVo=C9eQ@mail.gmail.com/T/#me55dc0987f9cc2acaa54372ce0492c65782be3fa
CC: stable@vger.kernel.org # 4.4+
Reviewed-by: Qu Wenruo <wqu@suse.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>
2019-12-17 20:34:48 +01:00
arch ARM: dts: pandora-common: define wl1251 as child node of mmc3 2019-12-17 20:34:36 +01:00
block block: call rq_qos_exit() after queue is frozen 2019-12-01 09:17:06 +01:00
certs export.h: remove VMLINUX_SYMBOL() and VMLINUX_SYMBOL_STR() 2018-08-22 23:21:44 +09:00
crypto crypto: user - fix memory leak in crypto_report 2019-12-13 08:52:48 +01:00
Documentation USB: documentation: flags on usb-storage versus UAS 2019-12-17 20:34:30 +01:00
drivers phy: renesas: rcar-gen3-usb2: Fix sysfs interface of "role" 2019-12-17 20:34:45 +01:00
firmware kbuild: remove all dummy assignments to obj- 2017-11-18 11:46:06 +09:00
fs Btrfs: send, skip backreference walking for extents with many references 2019-12-17 20:34:48 +01:00
include appletalk: Fix potential NULL pointer dereference in unregister_snap_client 2019-12-13 08:52:59 +01:00
init fork: fix some -Wmissing-prototypes warnings 2019-12-05 09:21:04 +01:00
ipc ipc/mqueue.c: only perform resource calculation if user valid 2019-08-06 19:06:52 +02:00
kernel sched/fair: Scale bandwidth quota and period without losing quota/period ratio precision 2019-12-13 08:52:35 +01:00
lib lib/genalloc.c: include vmalloc.h 2019-12-05 09:21:05 +01:00
LICENSES LICENSES: Remove CC-BY-SA-4.0 license text 2018-10-18 11:28:50 +02:00
mm mm/vmstat.c: fix NUMA statistics updates 2019-12-13 08:51:27 +01:00
net appletalk: Set error code if register_snap_client failed 2019-12-13 08:52:59 +01:00
samples vfio-mdev/samples: Use u8 instead of char for handle functions 2019-12-05 09:20:28 +01:00
scripts modpost: skip ELF local symbols during section mismatch check 2019-12-13 08:52:20 +01:00
security apparmor: delete the dentry in aafs_remove() to avoid a leak 2019-12-05 09:21:19 +01:00
sound ASoC: rsnd: fixup MIX kctrl registration 2019-12-13 08:52:57 +01:00
tools perf script: Fix invalid LBR/binary mismatch error 2019-12-13 08:52:55 +01:00
usr kbuild: clean compressed initramfs image 2019-10-07 18:57:16 +02:00
virt KVM: arm/arm64: vgic: Don't rely on the wrong pending table 2019-12-13 08:52:45 +01:00
.clang-format clang-format: Set IndentWrappedFunctionNames false 2018-08-01 18:38:51 +02:00
.cocciconfig
.get_maintainer.ignore
.gitattributes .gitattributes: set git diff driver for C source code files 2016-10-07 18:46:30 -07:00
.gitignore Kbuild updates for v4.17 (2nd) 2018-04-15 17:21:30 -07:00
.mailmap libnvdimm-for-4.19_misc 2018-08-25 18:13:10 -07:00
COPYING COPYING: use the new text with points to the license files 2018-03-23 12:41:45 -06:00
CREDITS 9p: remove Ron Minnich from MAINTAINERS 2018-08-17 16:20:26 -07:00
Kbuild Kbuild updates for v4.15 2017-11-17 17:45:29 -08:00
Kconfig kconfig: move the "Executable file formats" menu to fs/Kconfig.binfmt 2018-08-02 08:06:55 +09:00
MAINTAINERS USB: rio500: Remove Rio 500 kernel driver 2019-10-17 13:44:47 -07:00
Makefile Linux 4.19.89 2019-12-13 08:52:59 +01:00
README Docs: Added a pointer to the formatted docs to README 2018-03-21 09:02:53 -06:00

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.
See Documentation/00-INDEX for a list of what is contained in each file.

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.