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linux/fs/fuse
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Krister Johansen 706448f716 fuse: share lookup state between submount and its parent 
commit c4d361f66a upstream.

Fuse submounts do not perform a lookup for the nodeid that they inherit
from their parent.  Instead, the code decrements the nlookup on the
submount's fuse_inode when it is instantiated, and no forget is
performed when a submount root is evicted.

Trouble arises when the submount's parent is evicted despite the
submount itself being in use.  In this author's case, the submount was
in a container and deatched from the initial mount namespace via a
MNT_DEATCH operation.  When memory pressure triggered the shrinker, the
inode from the parent was evicted, which triggered enough forgets to
render the submount's nodeid invalid.

Since submounts should still function, even if their parent goes away,
solve this problem by sharing refcounted state between the parent and
its submount.  When all of the references on this shared state reach
zero, it's safe to forget the final lookup of the fuse nodeid.

Signed-off-by: Krister Johansen <kjlx@templeofstupid.com>
Cc: stable@vger.kernel.org
Fixes: 1866d779d5 ("fuse: Allow fuse_fill_super_common() for submounts")
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Signed-off-by: Krister Johansen <kjlx@templeofstupid.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
History 2024-01-01 12:39:08 +00:00
..
acl.c vfs: add rcu argument to ->get_acl() callback 2021-08-18 22:08:24 +02:00
control.c fuse: Remove the control interface for virtio-fs 2022-07-21 16:06:19 +02:00
cuse.c cuse: simplify refcount 2021-04-14 10:40:58 +02:00
dax.c fuse: dax: set fc->dax to NULL in fuse_dax_conn_free() 2023-12-20 17:00:20 +01:00
dev.c mm: multi-gen LRU: groundwork 2022-09-26 19:46:09 -07:00
dir.c fuse: revalidate: don't invalidate if interrupted 2023-07-27 08:50:25 +02:00
file.c attr: use consistent sgid stripping checks 2023-03-03 11:52:25 +01:00
fuse_i.h fuse: share lookup state between submount and its parent 2024-01-01 12:39:08 +00:00
inode.c fuse: share lookup state between submount and its parent 2024-01-01 12:39:08 +00:00
ioctl.c fuse: ioctl: translate ENOSYS in outarg 2023-07-27 08:50:25 +02:00
Kconfig dax: remove CONFIG_DAX_DRIVER 2021-12-04 08:58:51 -08:00
Makefile fuse: move ioctl to separate source file 2021-04-12 15:04:30 +02:00
readdir.c fuse: nlookup missing decrement in fuse_direntplus_link 2023-09-19 12:28:05 +02:00
virtio_fs.c virtio_fs: Modify format for virtio_fs_direct_access 2022-07-26 10:38:58 +02:00
xattr.c fuse: move fuse_invalidate_attr() into fuse_update_ctime() 2021-10-22 17:03:01 +02:00