linux.git/fs/overlayfs/export.c, branch v6.9

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
  ...

ovl: remove redundant ofs->indexdir member

2023-11-20T07:49:09+00:00

When the index feature is disabled, ofs->indexdir is NULL.
When the index feature is enabled, ofs->indexdir has the same value as
ofs->workdir and takes an extra reference.

This makes the code harder to understand when it is not always clear
that ofs->indexdir in one function is the same dentry as ofs->workdir
in another function.

Remove this redundancy, by referencing ofs->workdir directly in index
helpers and by using the ovl_indexdir() accessor in generic code.

Signed-off-by: Amir Goldstein

ovl: stop using d_alloc_anon()/d_instantiate_anon()

2023-11-18T21:15:19+00:00

Commit f9c34674bc60 ("vfs: factor out helpers d_instantiate_anon() and
d_alloc_anon()") was introduced so overlayfs could initialize a non-dir
disconnected overlay dentry before overlay inode is attached to it.

Since commit ("0af950f57fef ovl: move ovl_entry into ovl_inode"), all
ovl_obtain_alias() can do is set DCACHE_OP_*REVALIDATE flags in ->d_flags
and OVL_E_UPPER_ALIAS flag in ->d_fsdata.

The DCACHE_OP_*REVALIDATE flags and OVL_E_UPPER_ALIAS flag are irrelevant
for a disconnected non-dir dentry, so it is better to use d_obtain_alias()
instead of open coding it.

Suggested-by: Al Viro 
Signed-off-by: Amir Goldstein 
Signed-off-by: Al Viro

ovl: reorder ovl_want_write() after ovl_inode_lock()

2023-10-30T22:12:57+00:00

Make the locking order of ovl_inode_lock() strictly between the two
vfs stacked layers, i.e.:
- ovl vfs locks: sb_writers, inode_lock, ...
- ovl_inode_lock
- upper vfs locks: sb_writers, inode_lock, ...

To that effect, move ovl_want_write() into the helpers ovl_nlink_start()
and ovl_copy_up_start which currently take the ovl_inode_lock() after
ovl_want_write().

Signed-off-by: Amir Goldstein

ovl: fix NULL pointer defer when encoding non-decodable lower fid

2023-10-03T06:24:11+00:00

A wrong return value from ovl_check_encode_origin() would cause
ovl_dentry_to_fid() to try to encode fid from NULL upper dentry.

Reported-by: syzbot+2208f82282740c1c8915@syzkaller.appspotmail.com
Fixes: 16aac5ad1fa9 ("ovl: support encoding non-decodable file handles")
Signed-off-by: Amir Goldstein

ovl: make consistent use of OVL_FS()

2023-08-12T16:02:54+00:00

Always use OVL_FS() to retrieve the corresponding struct ovl_fs from a
struct super_block.

Reviewed-by: Amir Goldstein 
Signed-off-by: Andrea Righi 
Signed-off-by: Amir Goldstein

ovl: support encoding non-decodable file handles

2023-08-12T16:02:47+00:00

When all layers support file handles, we support encoding non-decodable
file handles (a.k.a. fid) even with nfs_export=off.

When file handles do not need to be decoded, we do not need to copy up
redirected lower directories on encode, and we encode also non-indexed
upper with lower file handle, so fid will not change on copy up.

This enables reporting fanotify events with file handles on overlayfs
with default config/mount options.

Signed-off-by: Amir Goldstein

ovl: deduplicate lowerpath and lowerstack[]

2023-06-19T11:01:13+00:00

The ovl_inode contains a copy of lowerpath in lowerstack[0], so the
lowerpath member can be removed.

Use accessor ovl_lowerpath() to get the lowerpath whereever the member
was accessed directly.

Signed-off-by: Amir Goldstein 
Signed-off-by: Miklos Szeredi

ovl: move ovl_entry into ovl_inode

2023-06-19T11:01:13+00:00

The lower stacks of all the ovl inode aliases should be identical
and there is redundant information in ovl_entry and ovl_inode.

Move lowerstack into ovl_inode and keep only the OVL_E_FLAGS
per overlay dentry.

Following patches will deduplicate redundant ovl_inode fields.

Note that for pure upper and negative dentries, OVL_E(dentry) may be
NULL now, so it is imporatnt to use the ovl_numlower() accessor.

Reviewed-by: Alexander Larsson 
Signed-off-by: Amir Goldstein 
Signed-off-by: Miklos Szeredi

ovl: use ovl_numlower() and ovl_lowerstack() accessors

2023-06-19T11:01:13+00:00

This helps fortify against dereferencing a NULL ovl_entry,
before we move the ovl_entry reference into ovl_inode.

Reviewed-by: Alexander Larsson 
Signed-off-by: Amir Goldstein 
Signed-off-by: Miklos Szeredi