WSL2-Linux-Kernel/fs/kernfs
Ian Kent 410d591a19 kernfs: don't create a negative dentry if inactive node exists
It's been reported that doing stress test for module insertion and
removal can result in an ENOENT from libkmod for a valid module.

In kernfs_iop_lookup() a negative dentry is created if there's no kernfs
node associated with the dentry or the node is inactive.

But inactive kernfs nodes are meant to be invisible to the VFS and
creating a negative dentry for these can have unexpected side effects
when the node transitions to an active state.

The point of creating negative dentries is to avoid the expensive
alloc/free cycle that occurs if there are frequent lookups for kernfs
attributes that don't exist. So kernfs nodes that are not yet active
should not result in a negative dentry being created so when they
transition to an active state VFS lookups can create an associated
dentry is a natural way.

It's also been reported that https://github.com/osandov/blktests.git
test block/001 hangs during the test. It was suggested that recent
changes to blktests might have caused it but applying this patch
resolved the problem without change to blktests.

Fixes: c7e7c04274 ("kernfs: use VFS negative dentry caching")
Tested-by: Yi Zhang <yi.zhang@redhat.com>
ACKed-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Ian Kent <raven@themaw.net>
Link: https://lore.kernel.org/r/163330943316.19450.15056895533949392922.stgit@mickey.themaw.net
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2021-10-04 10:27:18 +02:00
..
Kconfig treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
Makefile treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
dir.c kernfs: don't create a negative dentry if inactive node exists 2021-10-04 10:27:18 +02:00
file.c kernfs: switch kernfs to use an rwsem 2021-07-27 09:29:15 +02:00
inode.c kernfs: use i_lock to protect concurrent inode updates 2021-07-27 09:29:15 +02:00
kernfs-internal.h kernfs: switch kernfs to use an rwsem 2021-07-27 09:29:15 +02:00
mount.c kernfs: use i_lock to protect concurrent inode updates 2021-07-27 09:29:15 +02:00
symlink.c kernfs: switch kernfs to use an rwsem 2021-07-27 09:29:15 +02:00