linux/include
David Howells 9880150655 fscache: Fix the default for fscache_maybe_release_page()
Fix the default for fscache_maybe_release_page() for when the cookie isn't
valid or the page isn't cached.  It mustn't return false as that indicates
the page cannot yet be freed.

The problem with the default is that if, say, there's no cache, but a
network filesystem's pages are using up almost all the available memory, a
system can OOM because the filesystem ->releasepage() op will not allow
them to be released as fscache_maybe_release_page() incorrectly prevents
it.

This can be tested by writing a sequence of 512MiB files to an AFS mount.
It does not affect NFS or CIFS because both of those wrap the call in a
check of PG_fscache and it shouldn't bother Ceph as that only has
PG_private set whilst writeback is in progress.  This might be an issue for
9P, however.

Note that the pages aren't entirely stuck.  Removing a file or unmounting
will clear things because that uses ->invalidatepage() instead.

Fixes: 201a15428b ("FS-Cache: Handle pages pending storage that get evicted under OOM conditions")
Reported-by: Marc Dionne <marc.dionne@auristor.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Jeff Layton <jlayton@redhat.com>
Acked-by: Al Viro <viro@zeniv.linux.org.uk>
Tested-by: Marc Dionne <marc.dionne@auristor.com>
cc: stable@vger.kernel.org # 2.6.32+
2018-01-02 10:02:19 +00:00
..
acpi Merge branch 'acpi-ec' into acpi 2017-11-30 13:37:29 +01:00
asm-generic Merge branch 'x86-pti-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2017-12-23 11:53:04 -08:00
clocksource arm64 updates for 4.15 2017-11-15 10:56:56 -08:00
crypto Merge branch 'linus' of git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6 2017-12-22 12:22:48 -08:00
drm drm: rework delayed connector cleanup in connector_iter 2017-12-13 22:59:00 +01:00
dt-bindings fixes/cleanups for rc1, non-desktop flags for VR 2017-11-23 21:04:56 -10:00
keys
kvm KVM: arm/arm64: timer: Don't set irq as forwarded if no usable GIC 2017-12-18 10:53:23 +01:00
linux fscache: Fix the default for fscache_maybe_release_page() 2018-01-02 10:02:19 +00:00
math-emu
media media updates for v4.15-rc1 2017-11-15 20:30:12 -08:00
memory
misc
net sock: Add sock_owned_by_user_nocheck 2017-12-28 14:28:22 -05:00
pcmcia
ras
rdma Updates for 4.15 kernel merge window 2017-11-15 14:54:53 -08:00
scsi scsi: libsas: align sata_device's rps_resp on a cacheline 2017-11-21 23:06:32 -05:00
soc We have two changes to the core framework this time around. The first being a 2017-11-17 20:04:24 -08:00
sound ALSA: hda - Fix yet remaining issue with vmaster 0dB initialization 2017-11-22 12:34:56 +01:00
target Merge branch 'for-next' of git://git.kernel.org/pub/scm/linux/kernel/git/nab/target-pending 2017-11-24 19:19:20 -10:00
trace Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2017-12-28 23:20:21 -08:00
uapi Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2017-12-15 13:08:37 -08:00
video fbdev changes for v4.15: 2017-11-20 21:50:24 -10:00
xen xen: fixes for 4.15-rc5 2017-12-22 12:30:10 -08:00