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Hugh Dickins af53d3e9e0 mm: swapoff: shmem_unuse() stop eviction without igrab() 
The igrab() in shmem_unuse() looks good, but we forgot that it gives no
protection against concurrent unmounting: a point made by Konstantin
Khlebnikov eight years ago, and then fixed in 2.6.39 by 778dd893ae
("tmpfs: fix race between umount and swapoff").  The current 5.1-rc
swapoff is liable to hit "VFS: Busy inodes after unmount of tmpfs.
Self-destruct in 5 seconds.  Have a nice day..." followed by GPF.

Once again, give up on using igrab(); but don't go back to making such
heavy-handed use of shmem_swaplist_mutex as last time: that would spoil
the new design, and I expect could deadlock inside shmem_swapin_page().

Instead, shmem_unuse() just raise a "stop_eviction" count in the shmem-
specific inode, and shmem_evict_inode() wait for that to go down to 0.
Call it "stop_eviction" rather than "swapoff_busy" because it can be put
to use for others later (huge tmpfs patches expect to use it).

That simplifies shmem_unuse(), protecting it from both unlink and
unmount; and in practice lets it locate all the swap in its first try.
But do not rely on that: there's still a theoretical case, when
shmem_writepage() might have been preempted after its get_swap_page(),
before making the swap entry visible to swapoff.

[hughd@google.com: remove incorrect list_del()]
  Link: http://lkml.kernel.org/r/alpine.LSU.2.11.1904091133570.1898@eggly.anvils
Link: http://lkml.kernel.org/r/alpine.LSU.2.11.1904081259400.1523@eggly.anvils
Fixes: b56a2d8af9 ("mm: rid swapoff of quadratic complexity")
Signed-off-by: Hugh Dickins <hughd@google.com>
Cc: "Alex Xu (Hello71)" <alex_y_xu@yahoo.ca>
Cc: Huang Ying <ying.huang@intel.com>
Cc: Kelley Nielsen <kelleynnn@gmail.com>
Cc: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Cc: Rik van Riel <riel@surriel.com>
Cc: Vineeth Pillai <vpillai@digitalocean.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2019-04-19 09:46:04 -07:00
arch Avoid compiler uninitialised warning introduced by recent arm64 futex fix 2019-04-18 10:24:48 -07:00
block block: do not leak memory in bio_copy_user_iov() 2019-04-10 16:14:40 -06:00
certs kexec, KEYS: Make use of platform keyring for signature verify 2019-02-04 17:34:07 -05:00
crypto crypto: x86/poly1305 - fix overflow during partial reduction 2019-04-08 14:43:06 +08:00
Documentation rxrpc: Make rxrpc_kernel_check_life() indicate if call completed 2019-04-12 16:57:23 -07:00
drivers s390 update with bug fixes for 5.1-rc6 2019-04-18 08:15:06 -07:00
fs AFS fixes 2019-04-18 08:10:22 -07:00
include mm: swapoff: shmem_unuse() stop eviction without igrab() 2019-04-19 09:46:04 -07:00
init init/main: add checks for the return value of memblock_alloc*() 2019-03-12 10:04:02 -07:00
ipc Merge branch 'work.mount' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2019-03-12 14:08:19 -07:00
kernel signal: use fdget() since we don't allow O_PATH 2019-04-18 08:35:18 -07:00
lib Merge branch 'fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2019-04-09 16:20:59 -10:00
LICENSES LICENSES: Add GCC runtime library exception text 2019-01-16 14:54:15 -07:00
mm mm: swapoff: shmem_unuse() stop eviction without igrab() 2019-04-19 09:46:04 -07:00
net Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2019-04-17 09:57:45 -07:00
samples Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2019-03-11 08:54:01 -07:00
scripts fs: stream_open - opener for stream-like files so that read and write can run simultaneously without deadlock 2019-04-06 07:01:55 -10:00
security apparmor: Restore Y/N in /sys for apparmor's "enabled" 2019-04-10 04:24:48 -07:00
sound ASoC: Fixes for v5.1 2019-04-11 14:36:30 +02:00
tools Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2019-04-17 09:57:45 -07:00
usr user/Makefile: Fix typo and capitalization in comment section 2018-12-11 00:18:03 +09:00
virt KVM: fix spectrev1 gadgets 2019-04-16 15:38:07 +02:00
.clang-format clang-format: Update with the latest for_each macro list 2019-04-12 12:49:54 +02:00
.cocciconfig
.get_maintainer.ignore
.gitattributes
.gitignore kbuild: Add support for DT binding schema checks 2018-12-13 09:41:32 -06:00
.mailmap Update Nicolas Pitre's email address 2019-04-02 18:12:44 -10:00
COPYING COPYING: use the new text with points to the license files 2018-03-23 12:41:45 -06:00
CREDITS Char/Misc driver patches for 5.1-rc1 2019-03-06 14:18:59 -08:00
Kbuild Kbuild updates for v5.1 2019-03-10 17:48:21 -07:00
Kconfig kconfig: move the "Executable file formats" menu to fs/Kconfig.binfmt 2018-08-02 08:06:55 +09:00
MAINTAINERS Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2019-04-17 09:57:45 -07:00
Makefile Linux 5.1-rc5 2019-04-14 15:17:41 -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.