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Al Viro b0be96903d fast_dput(): handle underflows gracefully 
[ Upstream commit 504e08cebe ]

If refcount is less than 1, we should just warn, unlock dentry and
return true, so that the caller doesn't try to do anything else.

Taking care of that leaves the rest of "lockref_put_return() has
failed" case equivalent to "decrement refcount and rejoin the
normal slow path after the point where we grab ->d_lock".

NOTE: lockref_put_return() is strictly a fastpath thing - unlike
the rest of lockref primitives, it does not contain a fallback.
Caller (and it looks like fast_dput() is the only legitimate one
in the entire kernel) has to do that itself.  Reasons for
lockref_put_return() failures:
	* ->d_lock held by somebody
	* refcount <= 0
	* ... or an architecture not supporting lockref use of
cmpxchg - sparc, anything non-SMP, config with spinlock debugging...

We could add a fallback, but it would be a clumsy API - we'd have
to distinguish between:
	(1) refcount > 1 - decremented, lock not held on return
	(2) refcount < 1 - left alone, probably no sense to hold the lock
	(3) refcount is 1, no cmphxcg - decremented, lock held on return
	(4) refcount is 1, cmphxcg supported - decremented, lock *NOT* held
	    on return.
We want to return with no lock held in case (4); that's the whole point of that
thing.  We very much do not want to have the fallback in case (3) return without
a lock, since the caller might have to retake it in that case.
So it wouldn't be more convenient than doing the fallback in the caller and
it would be very easy to screw up, especially since the test coverage would
suck - no way to test (3) and (4) on the same kernel build.

Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
History 2024-02-05 20:16:57 +00:00
arch ARM: dts: usr8200: Fix phy registers 2024-02-05 20:16:56 +00:00
block block: prevent an integer overflow in bvec_try_merge_hw_page 2024-02-05 20:16:54 +00:00
certs This update includes the following changes: 2023-11-02 16:15:30 -10:00
crypto crypto: api - Disallow identical driver names 2024-01-31 16:20:54 -08:00
Documentation ASoC: doc: Fix undefined SND_SOC_DAPM_NOPM argument 2024-02-05 20:16:57 +00:00
drivers net: dsa: qca8k: put MDIO bus OF node on qca8k_mdio_register() failure 2024-02-05 20:16:56 +00:00
fs fast_dput(): handle underflows gracefully 2024-02-05 20:16:57 +00:00
include intel: add bit macro includes where needed 2024-02-05 20:16:55 +00:00
init rootfs: Fix support for rootfstype= when root= is given 2024-01-25 15:45:15 -08:00
io_uring io_uring: adjust defer tw counting 2024-01-25 15:45:30 -08:00
ipc Many singleton patches against the MM code. The patch series which are 2023-11-02 19:38:47 -10:00
kernel x86/cfi,bpf: Fix bpf_exception_cb() signature 2024-02-05 20:16:54 +00:00
lib kunit: Reset test->priv after each param iteration 2024-02-05 20:16:46 +00:00
LICENSES LICENSES: Add the copyleft-next-0.3.1 license 2022-11-08 15:44:01 +01:00
mm memblock: fix crash when reserved memory is not added to memory 2024-01-31 16:21:18 -08:00
net net: kcm: fix direct access to bv_len 2024-02-05 20:16:56 +00:00
rust rust: Ignore preserve-most functions 2024-01-25 15:45:09 -08:00
samples Landlock updates for v6.7-rc1 2023-11-03 09:28:53 -10:00
scripts scripts/get_abi: fix source path leak 2024-01-31 16:21:00 -08:00
security lsm: new security_file_ioctl_compat() hook 2024-01-31 16:21:00 -08:00
sound ALSA: hda: Refer to correct stream index at loops 2024-02-05 20:16:56 +00:00
tools libbpf: Fix NULL pointer dereference in bpf_object__collect_prog_relos 2024-02-05 20:16:55 +00:00
usr arch: Remove Itanium (IA-64) architecture 2023-09-11 08:13:17 +00:00
virt KVM/arm64 fixes for 6.7, part #2 2023-12-22 18:03:54 -05:00
.clang-format iommu: Add for_each_group_device() 2023-05-23 08:15:51 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore get_maintainer: add Alan to .get_maintainer.ignore 2022-08-20 15:17:44 -07:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore kbuild: rpm-pkg: generate kernel.spec in rpmbuild/SPECS/ 2023-10-03 20:49:09 +09:00
.mailmap 12 hotfixes. 2 are cc:stable and the remainder either address post-6.7 2024-01-05 13:46:18 -08:00
.rustfmt.toml rust: add .rustfmt.toml 2022-09-28 09:02:20 +02:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS 12 hotfixes. 2 are cc:stable and the remainder either address post-6.7 2024-01-05 13:46:18 -08:00
Kbuild Kbuild updates for v6.1 2022-10-10 12:00:45 -07:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS 12 hotfixes. 2 are cc:stable and the remainder either address post-6.7 2024-01-05 13:46:18 -08:00
Makefile Linux 6.7.3 2024-01-31 16:21:21 -08:00
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.