linux-stable.git/fs/libfs.c, branch linux-6.8.y

shmem: Fix shmem_rename2()

2024-05-30T07:49:00+00:00

[ Upstream commit ad191eb6d6942bb835a0b20b647f7c53c1d99ca4 ]

When renaming onto an existing directory entry, user space expects
the replacement entry to have the same directory offset as the
original one.

Link: https://gitlab.alpinelinux.org/alpine/aports/-/issues/15966
Fixes: a2e459555c5f ("shmem: stable directory offsets")
Signed-off-by: Chuck Lever 
Link: https://lore.kernel.org/r/20240415152057.4605-4-cel@kernel.org
Signed-off-by: Christian Brauner 
Signed-off-by: Sasha Levin

libfs: Add simple_offset_rename() API

2024-05-30T07:48:59+00:00

[ Upstream commit 5a1a25be995e1014abd01600479915683e356f5c ]

I'm about to fix a tmpfs rename bug that requires the use of
internal simple_offset helpers that are not available in mm/shmem.c

Signed-off-by: Chuck Lever 
Link: https://lore.kernel.org/r/20240415152057.4605-3-cel@kernel.org
Signed-off-by: Christian Brauner 
Stable-dep-of: ad191eb6d694 ("shmem: Fix shmem_rename2()")
Signed-off-by: Sasha Levin

libfs: Fix simple_offset_rename_exchange()

2024-05-30T07:48:59+00:00

[ Upstream commit 23cdd0eed3f1fff3af323092b0b88945a7950d8e ]

User space expects the replacement (old) directory entry to have
the same directory offset after the rename.

Suggested-by: Christian Brauner 
Fixes: a2e459555c5f ("shmem: stable directory offsets")
Signed-off-by: Chuck Lever 
Link: https://lore.kernel.org/r/20240415152057.4605-2-cel@kernel.org
Signed-off-by: Christian Brauner 
Signed-off-by: Sasha Levin

libfs: Convert simple directory offsets to use a Maple Tree

2024-05-30T07:48:59+00:00

[ Upstream commit 0e4a862174f2a8d1653a8a9cf0815020e1d3af24 ]

Test robot reports:
> kernel test robot noticed a -19.0% regression of aim9.disk_src.ops_per_sec on:
>
> commit: a2e459555c5f9da3e619b7e47a63f98574dc75f1 ("shmem: stable directory offsets")
> https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git master

Feng Tang further clarifies that:
> ... the new simple_offset_add()
> called by shmem_mknod() brings extra cost related with slab,
> specifically the 'radix_tree_node', which cause the regression.

Willy's analysis is that, over time, the test workload causes
xa_alloc_cyclic() to fragment the underlying SLAB cache.

This patch replaces the offset_ctx's xarray with a Maple Tree in the
hope that Maple Tree's dense node mode will handle this scenario
more scalably.

In addition, we can widen the simple directory offset maximum to
signed long (as loff_t is also signed).

Suggested-by: Matthew Wilcox 
Reported-by: kernel test robot 
Closes: https://lore.kernel.org/oe-lkp/202309081306.3ecb3734-oliver.sang@intel.com
Signed-off-by: Chuck Lever 
Link: https://lore.kernel.org/r/170820145616.6328.12620992971699079156.stgit@91.116.238.104.host.secureserver.net
Reviewed-by: Jan Kara 
Signed-off-by: Christian Brauner 
Stable-dep-of: 23cdd0eed3f1 ("libfs: Fix simple_offset_rename_exchange()")
Signed-off-by: Sasha Levin

libfs: Add simple_offset_empty()

2024-05-30T07:48:59+00:00

[ Upstream commit ecba88a3b32d733d41e27973e25b2bc580f64281 ]

For simple filesystems that use directory offset mapping, rely
strictly on the directory offset map to tell when a directory has
no children.

After this patch is applied, the emptiness test holds only the RCU
read lock when the directory being tested has no children.

In addition, this adds another layer of confirmation that
simple_offset_add/remove() are working as expected.

Reviewed-by: Jan Kara 
Signed-off-by: Chuck Lever 
Link: https://lore.kernel.org/r/170820143463.6328.7872919188371286951.stgit@91.116.238.104.host.secureserver.net
Signed-off-by: Christian Brauner 
Stable-dep-of: 23cdd0eed3f1 ("libfs: Fix simple_offset_rename_exchange()")
Signed-off-by: Sasha Levin

libfs: Define a minimum directory offset

2024-05-30T07:48:59+00:00

[ Upstream commit 7beea725a8ca412c6190090ce7c3a13b169592a1 ]

This value is used in several places, so make it a symbolic
constant.

Reviewed-by: Jan Kara 
Signed-off-by: Chuck Lever 
Link: https://lore.kernel.org/r/170820142741.6328.12428356024575347885.stgit@91.116.238.104.host.secureserver.net
Signed-off-by: Christian Brauner 
Stable-dep-of: 23cdd0eed3f1 ("libfs: Fix simple_offset_rename_exchange()")
Signed-off-by: Sasha Levin

libfs: Re-arrange locking in offset_iterate_dir()

2024-05-30T07:48:58+00:00

[ Upstream commit 3f6d810665dfde0d33785420618ceb03fba0619d ]

Liam and Matthew say that once the RCU read lock is released,
xa_state is not safe to re-use for the next xas_find() call. But the
RCU read lock must be released on each loop iteration so that
dput(), which might_sleep(), can be called safely.

Thus we are forced to walk the offset tree with fresh state for each
directory entry. xa_find() can do this for us, though it might be a
little less efficient than maintaining xa_state locally.

We believe that in the current code base, inode->i_rwsem provides
protection for the xa_state maintained in
offset_iterate_dir(). However, there is no guarantee that will
continue to be the case in the future.

Since offset_iterate_dir() doesn't build xa_state locally any more,
there's no longer a strong need for offset_find_next(). Clean up by
rolling these two helpers together.

Suggested-by: Liam R. Howlett 
Message-ID: <170785993027.11135.8830043889278631735.stgit@91.116.238.104.host.secureserver.net>
Signed-off-by: Chuck Lever 
Link: https://lore.kernel.org/r/170820142021.6328.15047865406275957018.stgit@91.116.238.104.host.secureserver.net
Reviewed-by: Jan Kara 
Signed-off-by: Christian Brauner 
Stable-dep-of: 23cdd0eed3f1 ("libfs: Fix simple_offset_rename_exchange()")
Signed-off-by: Sasha Levin

Merge tag 'pull-dcache' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs

2024-01-12T04:11:35+00:00

Pull dcache updates from Al Viro:
 "Change of locking rules for __dentry_kill(), regularized refcounting
  rules in that area, assorted cleanups and removal of weird corner
  cases (e.g. now ->d_iput() on child is always called before the parent
  might hit __dentry_kill(), etc)"

* tag 'pull-dcache' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: (40 commits)
  dcache: remove unnecessary NULL check in dget_dlock()
  kill DCACHE_MAY_FREE
  __d_unalias() doesn't use inode argument
  d_alloc_parallel(): in-lookup hash insertion doesn't need an RCU variant
  get rid of DCACHE_GENOCIDE
  d_genocide(): move the extern into fs/internal.h
  simple_fill_super(): don't bother with d_genocide() on failure
  nsfs: use d_make_root()
  d_alloc_pseudo(): move setting ->d_op there from the (sole) caller
  kill d_instantate_anon(), fold __d_instantiate_anon() into remaining caller
  retain_dentry(): introduce a trimmed-down lockless variant
  __dentry_kill(): new locking scheme
  d_prune_aliases(): use a shrink list
  switch select_collect{,2}() to use of to_shrink_list()
  to_shrink_list(): call only if refcount is 0
  fold dentry_kill() into dput()
  don't try to cut corners in shrink_lock_dentry()
  fold the call of retain_dentry() into fast_dput()
  Call retain_dentry() with refcount 0
  dentry_kill(): don't bother with retain_dentry() on slow path
  ...

Merge branches 'work.dcache-misc' and 'work.dcache2' into work.dcache

2023-11-25T07:51:35+00:00

simple_fill_super(): don't bother with d_genocide() on failure

2023-11-25T07:50:11+00:00

Failing ->fill_super() will be followed by ->kill_sb(), which should
include kill_litter_super() if the call of simple_fill_super() had
been asked to create anything besides the root dentry.  So there's
no need to empty the partially populated tree - it will be trimmed
by inevitable kill_litter_super().

Signed-off-by: Al Viro