J. Bruce Fields 40595cdc93 nfs: block notification on fs with its own ->lock ... NFSv4.1 supports an optional lock notification feature which notifies the client when a lock comes available. (Normally NFSv4 clients just poll for locks if necessary.) To make that work, we need to request a blocking lock from the filesystem. We turned that off for NFS in commit f657f8eef3 ("nfs: don't atempt blocking locks on nfs reexports") [sic] because it actually blocks the nfsd thread while waiting for the lock. Thanks to Vasily Averin for pointing out that NFS isn't the only filesystem with that problem. Any filesystem that leaves ->lock NULL will use posix_lock_file(), which does the right thing. Simplest is just to assume that any filesystem that defines its own ->lock is not safe to request a blocking lock from. So, this patch mostly reverts commit f657f8eef3 ("nfs: don't atempt blocking locks on nfs reexports") [sic] and commit b840be2f00 ("lockd: don't attempt blocking locks on nfs reexports"), and instead uses a check of ->lock (Vasily's suggestion) to decide whether to support blocking lock notifications on a given filesystem. Also add a little documentation. Perhaps someday we could add back an export flag later to allow filesystems with "good" ->lock methods to support blocking lock notifications. Reported-by: Vasily Averin <vvs@virtuozzo.com> Signed-off-by: J. Bruce Fields <bfields@redhat.com> [ cel: Description rewritten to address checkpatch nits ] [ cel: Fixed warning when SUNRPC debugging is disabled ] [ cel: Fixed NULL check ] Signed-off-by: Chuck Lever <chuck.lever@oracle.com> Reviewed-by: Vasily Averin <vvs@virtuozzo.com>		2022-01-08 14:42:01 -05:00
..
acpi	Merge branches 'acpica', 'acpi-ec', 'acpi-pmic' and 'acpi-video'	2021-11-10 14:03:14 +01:00
asm-generic	Add linux/cacheflush.h	2021-11-17 10:36:15 -05:00
clocksource
crypto
drm	Removed the TTM Huge Page functionnality to address a crash, a timeout	2021-11-11 08:14:19 +10:00
dt-bindings	dt-bindings: Rename Ingenic CGU headers to ingenic,*.h	2021-11-11 22:27:14 -06:00
keys
kunit	include/kunit/test.h: replace kernel.h with the necessary inclusions	2021-11-09 10:02:49 -08:00
kvm
linux	nfs: block notification on fs with its own ->lock	2022-01-08 14:42:01 -05:00
math-emu
media	Merge branch 'akpm' (patches from Andrew)	2021-11-09 10:11:53 -08:00
memory
misc
net	Merge git://git.kernel.org/pub/scm/linux/kernel/git/pablo/nf	2021-12-08 17:02:35 -08:00
pcmcia
ras
rdma	RDMA/netlink: Add __maybe_unused to static inline in C file	2021-11-16 13:13:08 -04:00
scsi	SCSI misc on 20211112	2021-11-12 12:25:50 -08:00
soc	net: mscc: ocelot: create a function that replaces an existing VCAP filter	2021-11-26 11:38:20 -08:00
sound	ASoC: Fixes for v5.16	2021-11-25 14:35:24 +01:00
target
trace	SUNRPC: Remove low signal-to-noise tracepoints	2021-12-13 13:43:00 -05:00
uapi	Merge branch 'akpm' (patches from Andrew)	2021-12-11 08:46:52 -08:00
vdso
video
xen	xen: add "not_essential" flag to struct xenbus_driver	2021-11-23 13:41:29 -06:00