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Filipe Manana 5a656c3628 btrfs: stop doing GFP_KERNEL memory allocations in the ref verify tool 
In commit 351cbf6e44 ("btrfs: use nofs allocations for running delayed
items") we wrapped all btree updates when running delayed items with
memalloc_nofs_save() and memalloc_nofs_restore(), due to a lock inversion
detected by lockdep involving reclaim and the mutex of delayed nodes.

The problem is because the ref verify tool does some memory allocations
with GFP_KERNEL, which can trigger reclaim and reclaim can trigger inode
eviction, which requires locking the mutex of an inode's delayed node.
On the other hand the ref verify tool is called when allocating metadata
extents as part of operations that modify a btree, which is a problem when
running delayed nodes, where we do btree updates while holding the mutex
of a delayed node. This is what caused the lockdep warning.

Instead of wrapping every btree update when running delayed nodes, change
the ref verify tool to never do GFP_KERNEL allocations, because:

1) We get less repeated code, which at the moment does not even have a
   comment mentioning why we need to setup the NOFS context, which is a
   recommended good practice as mentioned at
   Documentation/core-api/gfp_mask-from-fs-io.rst

2) The ref verify tool is something meant only for debugging and not
   something that should be enabled on non-debug / non-development
   kernels;

3) We may have yet more places outside delayed-inode.c where we have
   similar problem: doing btree updates while holding some lock and
   then having the GFP_KERNEL memory allocations, from the ref verify
   tool, trigger reclaim and trying again to acquire the same lock
   through the reclaim path.
   Or we could get more such cases in the future, therefore this change
   prevents getting into similar cases when using the ref verify tool.

Curiously most of the memory allocations done by the ref verify tool
were already using GFP_NOFS, except a few ones for no apparent reason.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
2021-08-23 13:19:00 +02:00
arch powerpc fixes for 5.14 #6 2021-08-22 09:49:31 -07:00
block block-5.14-2021-08-20 2021-08-21 08:11:22 -07:00
certs Kbuild updates for v5.13 (2nd) 2021-05-08 10:00:11 -07:00
crypto crypto: drbg - select SHA512 2021-07-16 15:49:31 +08:00
Documentation RISC-V Fixes for 5.14-rc7 2021-08-21 11:04:26 -07:00
drivers Two clk driver fixes 2021-08-21 11:27:16 -07:00
fs btrfs: stop doing GFP_KERNEL memory allocations in the ref verify tool 2021-08-23 13:19:00 +02:00
include Merge branch 'akpm' (patches from Andrew) 2021-08-20 13:08:56 -07:00
init init: Suppress wrong warning for bootconfig cmdline parameter 2021-08-12 13:35:57 -04:00
ipc Merge branch 'akpm' (patches from Andrew) 2021-07-02 12:08:10 -07:00
kernel Networking fixes for 5.14-rc7, including fixes from bpf, wireless and 2021-08-19 12:33:43 -07:00
lib lib: use PFN_PHYS() in devmem_is_allowed() 2021-08-13 14:09:32 -10:00
LICENSES LICENSES/dual/CC-BY-4.0: Git rid of "smart quotes" 2021-07-15 06:31:24 -06:00
mm hugetlb: don't pass page cache pages to restore_reserve_on_error 2021-08-20 11:31:42 -07:00
net mptcp: full fully established support after ADD_ADDR 2021-08-19 12:16:54 +01:00
samples Networking fixes for 5.14-rc2, including fixes from bpf and netfilter. 2021-07-14 09:24:32 -07:00
scripts Kbuild fixes for v5.14 (2nd) 2021-08-07 10:03:02 -07:00
security bpf: Add lockdown check for probe_write_user helper 2021-08-10 10:10:10 +02:00
sound another sound-fixes for 5.14-rc7 2021-08-20 12:31:10 -07:00
tools Networking fixes for 5.14-rc7, including fixes from bpf, wireless and 2021-08-19 12:33:43 -07:00
usr .gitignore: prefix local generated files with a slash 2021-05-02 00:43:35 +09:00
virt KVM: Do not leak memory for duplicate debugfs directories 2021-08-04 06:02:03 -04:00
.clang-format clang-format: Update with the latest for_each macro list 2021-05-12 23:32:39 +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 .gitignore: ignore only top-level modules.builtin 2021-05-02 00:43:35 +09:00
.mailmap m68k updates for v5.14 2021-06-28 14:01:03 -07:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: move Murali Karicheri to credits 2021-04-29 15:47:30 -07:00
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 Merge branch 'akpm' (patches from Andrew) 2021-08-20 13:08:56 -07:00
Makefile Linux 5.14-rc7 2021-08-22 14:24:56 -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.