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Filename Latest commit message Latest commit date
David Rientjes 0bae7e7fac mm, thp: fix defrag setting if newline is not used
commit f42f25526502d851d0e3ca1e46297da8aafce8a7 upstream.

If thp defrag setting "defer" is used and a newline is *not* used when
writing to the sysfs file, this is interpreted as the "defer+madvise"
option.

This is because we do prefix matching and if five characters are written
without a newline, the current code ends up comparing to the first five
bytes of the "defer+madvise" option and using that instead.

Use the more appropriate sysfs_streq() that handles the trailing newline
for us.  Since this doubles as a nice cleanup, do it in enabled_store()
as well.

The current implementation relies on prefix matching: the number of
bytes compared is either the number of bytes written or the length of
the option being compared.  With a newline, "defer\n" does not match
"defer+"madvise"; without a newline, however, "defer" is considered to
match "defer+madvise" (prefix matching is only comparing the first five
bytes).  End result is that writing "defer" is broken unless it has an
additional trailing character.

This means that writing "madv" in the past would match and set
"madvise".  With strict checking, that no longer is the case but it is
unlikely anybody is currently doing this.

Link: http://lkml.kernel.org/r/alpine.DEB.2.21.2001171411020.56385@chino.kir.corp.google.com
Fixes: 21440d7eb9 ("mm, thp: add new defer+madvise defrag option")
Signed-off-by: David Rientjes <rientjes@google.com>
Suggested-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Mel Gorman <mgorman@techsingularity.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2020-03-05 16:43:51 +01:00
arch KVM: x86: Remove spurious clearing of async #PF MSR 2020-03-05 16:43:50 +01:00
block
certs
crypto
Documentation netfilter: nf_flowtable: fix documentation 2020-03-05 16:43:51 +01:00
drivers bus: tegra-aconnect: Remove PM_CLK dependency 2020-03-05 16:43:51 +01:00
fs xfs: clear kernel only flags in XFS_IOC_ATTRMULTI_BY_HANDLE 2020-03-05 16:43:51 +01:00
include lib/vdso: Make __arch_update_vdso_data() logic understandable 2020-03-05 16:43:49 +01:00
init
ipc
kernel locking/lockdep: Fix lockdep_stats indentation problem 2020-03-05 16:43:51 +01:00
lib kbuild: move headers_check rule to usr/include/Makefile 2020-03-05 16:43:47 +01:00
LICENSES
mm mm, thp: fix defrag setting if newline is not used 2020-03-05 16:43:51 +01:00
net netfilter: nft_tunnel: no need to call htons() when dumping ports 2020-03-05 16:43:50 +01:00
samples
scripts kbuild: move headers_check rule to usr/include/Makefile 2020-03-05 16:43:47 +01:00
security ima: ima/lsm policy rule loading logic bug fixes 2020-03-05 16:43:49 +01:00
sound
tools perf ui gtk: Add missing zalloc object 2020-03-05 16:43:50 +01:00
usr kbuild: move headers_check rule to usr/include/Makefile 2020-03-05 16:43:47 +01:00
virt KVM: Check for a bad hva before dropping into the ghc slow path 2020-03-05 16:43:48 +01:00
.clang-format
.cocciconfig
.get_maintainer.ignore
.gitattributes
.gitignore
.mailmap
COPYING
CREDITS
Kbuild
Kconfig
MAINTAINERS
Makefile kbuild: make single target builds even faster 2020-03-05 16:43:48 +01:00
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.