mirror of https://github.com/Qortal/Brooklyn
You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
910 lines
29 KiB
910 lines
29 KiB
==================== |
|
Changes since 2.5.0: |
|
==================== |
|
|
|
--- |
|
|
|
**recommended** |
|
|
|
New helpers: sb_bread(), sb_getblk(), sb_find_get_block(), set_bh(), |
|
sb_set_blocksize() and sb_min_blocksize(). |
|
|
|
Use them. |
|
|
|
(sb_find_get_block() replaces 2.4's get_hash_table()) |
|
|
|
--- |
|
|
|
**recommended** |
|
|
|
New methods: ->alloc_inode() and ->destroy_inode(). |
|
|
|
Remove inode->u.foo_inode_i |
|
|
|
Declare:: |
|
|
|
struct foo_inode_info { |
|
/* fs-private stuff */ |
|
struct inode vfs_inode; |
|
}; |
|
static inline struct foo_inode_info *FOO_I(struct inode *inode) |
|
{ |
|
return list_entry(inode, struct foo_inode_info, vfs_inode); |
|
} |
|
|
|
Use FOO_I(inode) instead of &inode->u.foo_inode_i; |
|
|
|
Add foo_alloc_inode() and foo_destroy_inode() - the former should allocate |
|
foo_inode_info and return the address of ->vfs_inode, the latter should free |
|
FOO_I(inode) (see in-tree filesystems for examples). |
|
|
|
Make them ->alloc_inode and ->destroy_inode in your super_operations. |
|
|
|
Keep in mind that now you need explicit initialization of private data |
|
typically between calling iget_locked() and unlocking the inode. |
|
|
|
At some point that will become mandatory. |
|
|
|
--- |
|
|
|
**mandatory** |
|
|
|
Change of file_system_type method (->read_super to ->get_sb) |
|
|
|
->read_super() is no more. Ditto for DECLARE_FSTYPE and DECLARE_FSTYPE_DEV. |
|
|
|
Turn your foo_read_super() into a function that would return 0 in case of |
|
success and negative number in case of error (-EINVAL unless you have more |
|
informative error value to report). Call it foo_fill_super(). Now declare:: |
|
|
|
int foo_get_sb(struct file_system_type *fs_type, |
|
int flags, const char *dev_name, void *data, struct vfsmount *mnt) |
|
{ |
|
return get_sb_bdev(fs_type, flags, dev_name, data, foo_fill_super, |
|
mnt); |
|
} |
|
|
|
(or similar with s/bdev/nodev/ or s/bdev/single/, depending on the kind of |
|
filesystem). |
|
|
|
Replace DECLARE_FSTYPE... with explicit initializer and have ->get_sb set as |
|
foo_get_sb. |
|
|
|
--- |
|
|
|
**mandatory** |
|
|
|
Locking change: ->s_vfs_rename_sem is taken only by cross-directory renames. |
|
Most likely there is no need to change anything, but if you relied on |
|
global exclusion between renames for some internal purpose - you need to |
|
change your internal locking. Otherwise exclusion warranties remain the |
|
same (i.e. parents and victim are locked, etc.). |
|
|
|
--- |
|
|
|
**informational** |
|
|
|
Now we have the exclusion between ->lookup() and directory removal (by |
|
->rmdir() and ->rename()). If you used to need that exclusion and do |
|
it by internal locking (most of filesystems couldn't care less) - you |
|
can relax your locking. |
|
|
|
--- |
|
|
|
**mandatory** |
|
|
|
->lookup(), ->truncate(), ->create(), ->unlink(), ->mknod(), ->mkdir(), |
|
->rmdir(), ->link(), ->lseek(), ->symlink(), ->rename() |
|
and ->readdir() are called without BKL now. Grab it on entry, drop upon return |
|
- that will guarantee the same locking you used to have. If your method or its |
|
parts do not need BKL - better yet, now you can shift lock_kernel() and |
|
unlock_kernel() so that they would protect exactly what needs to be |
|
protected. |
|
|
|
--- |
|
|
|
**mandatory** |
|
|
|
BKL is also moved from around sb operations. BKL should have been shifted into |
|
individual fs sb_op functions. If you don't need it, remove it. |
|
|
|
--- |
|
|
|
**informational** |
|
|
|
check for ->link() target not being a directory is done by callers. Feel |
|
free to drop it... |
|
|
|
--- |
|
|
|
**informational** |
|
|
|
->link() callers hold ->i_mutex on the object we are linking to. Some of your |
|
problems might be over... |
|
|
|
--- |
|
|
|
**mandatory** |
|
|
|
new file_system_type method - kill_sb(superblock). If you are converting |
|
an existing filesystem, set it according to ->fs_flags:: |
|
|
|
FS_REQUIRES_DEV - kill_block_super |
|
FS_LITTER - kill_litter_super |
|
neither - kill_anon_super |
|
|
|
FS_LITTER is gone - just remove it from fs_flags. |
|
|
|
--- |
|
|
|
**mandatory** |
|
|
|
FS_SINGLE is gone (actually, that had happened back when ->get_sb() |
|
went in - and hadn't been documented ;-/). Just remove it from fs_flags |
|
(and see ->get_sb() entry for other actions). |
|
|
|
--- |
|
|
|
**mandatory** |
|
|
|
->setattr() is called without BKL now. Caller _always_ holds ->i_mutex, so |
|
watch for ->i_mutex-grabbing code that might be used by your ->setattr(). |
|
Callers of notify_change() need ->i_mutex now. |
|
|
|
--- |
|
|
|
**recommended** |
|
|
|
New super_block field ``struct export_operations *s_export_op`` for |
|
explicit support for exporting, e.g. via NFS. The structure is fully |
|
documented at its declaration in include/linux/fs.h, and in |
|
Documentation/filesystems/nfs/exporting.rst. |
|
|
|
Briefly it allows for the definition of decode_fh and encode_fh operations |
|
to encode and decode filehandles, and allows the filesystem to use |
|
a standard helper function for decode_fh, and provide file-system specific |
|
support for this helper, particularly get_parent. |
|
|
|
It is planned that this will be required for exporting once the code |
|
settles down a bit. |
|
|
|
**mandatory** |
|
|
|
s_export_op is now required for exporting a filesystem. |
|
isofs, ext2, ext3, resierfs, fat |
|
can be used as examples of very different filesystems. |
|
|
|
--- |
|
|
|
**mandatory** |
|
|
|
iget4() and the read_inode2 callback have been superseded by iget5_locked() |
|
which has the following prototype:: |
|
|
|
struct inode *iget5_locked(struct super_block *sb, unsigned long ino, |
|
int (*test)(struct inode *, void *), |
|
int (*set)(struct inode *, void *), |
|
void *data); |
|
|
|
'test' is an additional function that can be used when the inode |
|
number is not sufficient to identify the actual file object. 'set' |
|
should be a non-blocking function that initializes those parts of a |
|
newly created inode to allow the test function to succeed. 'data' is |
|
passed as an opaque value to both test and set functions. |
|
|
|
When the inode has been created by iget5_locked(), it will be returned with the |
|
I_NEW flag set and will still be locked. The filesystem then needs to finalize |
|
the initialization. Once the inode is initialized it must be unlocked by |
|
calling unlock_new_inode(). |
|
|
|
The filesystem is responsible for setting (and possibly testing) i_ino |
|
when appropriate. There is also a simpler iget_locked function that |
|
just takes the superblock and inode number as arguments and does the |
|
test and set for you. |
|
|
|
e.g.:: |
|
|
|
inode = iget_locked(sb, ino); |
|
if (inode->i_state & I_NEW) { |
|
err = read_inode_from_disk(inode); |
|
if (err < 0) { |
|
iget_failed(inode); |
|
return err; |
|
} |
|
unlock_new_inode(inode); |
|
} |
|
|
|
Note that if the process of setting up a new inode fails, then iget_failed() |
|
should be called on the inode to render it dead, and an appropriate error |
|
should be passed back to the caller. |
|
|
|
--- |
|
|
|
**recommended** |
|
|
|
->getattr() finally getting used. See instances in nfs, minix, etc. |
|
|
|
--- |
|
|
|
**mandatory** |
|
|
|
->revalidate() is gone. If your filesystem had it - provide ->getattr() |
|
and let it call whatever you had as ->revlidate() + (for symlinks that |
|
had ->revalidate()) add calls in ->follow_link()/->readlink(). |
|
|
|
--- |
|
|
|
**mandatory** |
|
|
|
->d_parent changes are not protected by BKL anymore. Read access is safe |
|
if at least one of the following is true: |
|
|
|
* filesystem has no cross-directory rename() |
|
* we know that parent had been locked (e.g. we are looking at |
|
->d_parent of ->lookup() argument). |
|
* we are called from ->rename(). |
|
* the child's ->d_lock is held |
|
|
|
Audit your code and add locking if needed. Notice that any place that is |
|
not protected by the conditions above is risky even in the old tree - you |
|
had been relying on BKL and that's prone to screwups. Old tree had quite |
|
a few holes of that kind - unprotected access to ->d_parent leading to |
|
anything from oops to silent memory corruption. |
|
|
|
--- |
|
|
|
**mandatory** |
|
|
|
FS_NOMOUNT is gone. If you use it - just set SB_NOUSER in flags |
|
(see rootfs for one kind of solution and bdev/socket/pipe for another). |
|
|
|
--- |
|
|
|
**recommended** |
|
|
|
Use bdev_read_only(bdev) instead of is_read_only(kdev). The latter |
|
is still alive, but only because of the mess in drivers/s390/block/dasd.c. |
|
As soon as it gets fixed is_read_only() will die. |
|
|
|
--- |
|
|
|
**mandatory** |
|
|
|
->permission() is called without BKL now. Grab it on entry, drop upon |
|
return - that will guarantee the same locking you used to have. If |
|
your method or its parts do not need BKL - better yet, now you can |
|
shift lock_kernel() and unlock_kernel() so that they would protect |
|
exactly what needs to be protected. |
|
|
|
--- |
|
|
|
**mandatory** |
|
|
|
->statfs() is now called without BKL held. BKL should have been |
|
shifted into individual fs sb_op functions where it's not clear that |
|
it's safe to remove it. If you don't need it, remove it. |
|
|
|
--- |
|
|
|
**mandatory** |
|
|
|
is_read_only() is gone; use bdev_read_only() instead. |
|
|
|
--- |
|
|
|
**mandatory** |
|
|
|
destroy_buffers() is gone; use invalidate_bdev(). |
|
|
|
--- |
|
|
|
**mandatory** |
|
|
|
fsync_dev() is gone; use fsync_bdev(). NOTE: lvm breakage is |
|
deliberate; as soon as struct block_device * is propagated in a reasonable |
|
way by that code fixing will become trivial; until then nothing can be |
|
done. |
|
|
|
**mandatory** |
|
|
|
block truncatation on error exit from ->write_begin, and ->direct_IO |
|
moved from generic methods (block_write_begin, cont_write_begin, |
|
nobh_write_begin, blockdev_direct_IO*) to callers. Take a look at |
|
ext2_write_failed and callers for an example. |
|
|
|
**mandatory** |
|
|
|
->truncate is gone. The whole truncate sequence needs to be |
|
implemented in ->setattr, which is now mandatory for filesystems |
|
implementing on-disk size changes. Start with a copy of the old inode_setattr |
|
and vmtruncate, and the reorder the vmtruncate + foofs_vmtruncate sequence to |
|
be in order of zeroing blocks using block_truncate_page or similar helpers, |
|
size update and on finally on-disk truncation which should not fail. |
|
setattr_prepare (which used to be inode_change_ok) now includes the size checks |
|
for ATTR_SIZE and must be called in the beginning of ->setattr unconditionally. |
|
|
|
**mandatory** |
|
|
|
->clear_inode() and ->delete_inode() are gone; ->evict_inode() should |
|
be used instead. It gets called whenever the inode is evicted, whether it has |
|
remaining links or not. Caller does *not* evict the pagecache or inode-associated |
|
metadata buffers; the method has to use truncate_inode_pages_final() to get rid |
|
of those. Caller makes sure async writeback cannot be running for the inode while |
|
(or after) ->evict_inode() is called. |
|
|
|
->drop_inode() returns int now; it's called on final iput() with |
|
inode->i_lock held and it returns true if filesystems wants the inode to be |
|
dropped. As before, generic_drop_inode() is still the default and it's been |
|
updated appropriately. generic_delete_inode() is also alive and it consists |
|
simply of return 1. Note that all actual eviction work is done by caller after |
|
->drop_inode() returns. |
|
|
|
As before, clear_inode() must be called exactly once on each call of |
|
->evict_inode() (as it used to be for each call of ->delete_inode()). Unlike |
|
before, if you are using inode-associated metadata buffers (i.e. |
|
mark_buffer_dirty_inode()), it's your responsibility to call |
|
invalidate_inode_buffers() before clear_inode(). |
|
|
|
NOTE: checking i_nlink in the beginning of ->write_inode() and bailing out |
|
if it's zero is not *and* *never* *had* *been* enough. Final unlink() and iput() |
|
may happen while the inode is in the middle of ->write_inode(); e.g. if you blindly |
|
free the on-disk inode, you may end up doing that while ->write_inode() is writing |
|
to it. |
|
|
|
--- |
|
|
|
**mandatory** |
|
|
|
.d_delete() now only advises the dcache as to whether or not to cache |
|
unreferenced dentries, and is now only called when the dentry refcount goes to |
|
0. Even on 0 refcount transition, it must be able to tolerate being called 0, |
|
1, or more times (eg. constant, idempotent). |
|
|
|
--- |
|
|
|
**mandatory** |
|
|
|
.d_compare() calling convention and locking rules are significantly |
|
changed. Read updated documentation in Documentation/filesystems/vfs.rst (and |
|
look at examples of other filesystems) for guidance. |
|
|
|
--- |
|
|
|
**mandatory** |
|
|
|
.d_hash() calling convention and locking rules are significantly |
|
changed. Read updated documentation in Documentation/filesystems/vfs.rst (and |
|
look at examples of other filesystems) for guidance. |
|
|
|
--- |
|
|
|
**mandatory** |
|
|
|
dcache_lock is gone, replaced by fine grained locks. See fs/dcache.c |
|
for details of what locks to replace dcache_lock with in order to protect |
|
particular things. Most of the time, a filesystem only needs ->d_lock, which |
|
protects *all* the dcache state of a given dentry. |
|
|
|
--- |
|
|
|
**mandatory** |
|
|
|
Filesystems must RCU-free their inodes, if they can have been accessed |
|
via rcu-walk path walk (basically, if the file can have had a path name in the |
|
vfs namespace). |
|
|
|
Even though i_dentry and i_rcu share storage in a union, we will |
|
initialize the former in inode_init_always(), so just leave it alone in |
|
the callback. It used to be necessary to clean it there, but not anymore |
|
(starting at 3.2). |
|
|
|
--- |
|
|
|
**recommended** |
|
|
|
vfs now tries to do path walking in "rcu-walk mode", which avoids |
|
atomic operations and scalability hazards on dentries and inodes (see |
|
Documentation/filesystems/path-lookup.txt). d_hash and d_compare changes |
|
(above) are examples of the changes required to support this. For more complex |
|
filesystem callbacks, the vfs drops out of rcu-walk mode before the fs call, so |
|
no changes are required to the filesystem. However, this is costly and loses |
|
the benefits of rcu-walk mode. We will begin to add filesystem callbacks that |
|
are rcu-walk aware, shown below. Filesystems should take advantage of this |
|
where possible. |
|
|
|
--- |
|
|
|
**mandatory** |
|
|
|
d_revalidate is a callback that is made on every path element (if |
|
the filesystem provides it), which requires dropping out of rcu-walk mode. This |
|
may now be called in rcu-walk mode (nd->flags & LOOKUP_RCU). -ECHILD should be |
|
returned if the filesystem cannot handle rcu-walk. See |
|
Documentation/filesystems/vfs.rst for more details. |
|
|
|
permission is an inode permission check that is called on many or all |
|
directory inodes on the way down a path walk (to check for exec permission). It |
|
must now be rcu-walk aware (mask & MAY_NOT_BLOCK). See |
|
Documentation/filesystems/vfs.rst for more details. |
|
|
|
--- |
|
|
|
**mandatory** |
|
|
|
In ->fallocate() you must check the mode option passed in. If your |
|
filesystem does not support hole punching (deallocating space in the middle of a |
|
file) you must return -EOPNOTSUPP if FALLOC_FL_PUNCH_HOLE is set in mode. |
|
Currently you can only have FALLOC_FL_PUNCH_HOLE with FALLOC_FL_KEEP_SIZE set, |
|
so the i_size should not change when hole punching, even when puching the end of |
|
a file off. |
|
|
|
--- |
|
|
|
**mandatory** |
|
|
|
->get_sb() is gone. Switch to use of ->mount(). Typically it's just |
|
a matter of switching from calling ``get_sb_``... to ``mount_``... and changing |
|
the function type. If you were doing it manually, just switch from setting |
|
->mnt_root to some pointer to returning that pointer. On errors return |
|
ERR_PTR(...). |
|
|
|
--- |
|
|
|
**mandatory** |
|
|
|
->permission() and generic_permission()have lost flags |
|
argument; instead of passing IPERM_FLAG_RCU we add MAY_NOT_BLOCK into mask. |
|
|
|
generic_permission() has also lost the check_acl argument; ACL checking |
|
has been taken to VFS and filesystems need to provide a non-NULL ->i_op->get_acl |
|
to read an ACL from disk. |
|
|
|
--- |
|
|
|
**mandatory** |
|
|
|
If you implement your own ->llseek() you must handle SEEK_HOLE and |
|
SEEK_DATA. You can hanle this by returning -EINVAL, but it would be nicer to |
|
support it in some way. The generic handler assumes that the entire file is |
|
data and there is a virtual hole at the end of the file. So if the provided |
|
offset is less than i_size and SEEK_DATA is specified, return the same offset. |
|
If the above is true for the offset and you are given SEEK_HOLE, return the end |
|
of the file. If the offset is i_size or greater return -ENXIO in either case. |
|
|
|
**mandatory** |
|
|
|
If you have your own ->fsync() you must make sure to call |
|
filemap_write_and_wait_range() so that all dirty pages are synced out properly. |
|
You must also keep in mind that ->fsync() is not called with i_mutex held |
|
anymore, so if you require i_mutex locking you must make sure to take it and |
|
release it yourself. |
|
|
|
--- |
|
|
|
**mandatory** |
|
|
|
d_alloc_root() is gone, along with a lot of bugs caused by code |
|
misusing it. Replacement: d_make_root(inode). On success d_make_root(inode) |
|
allocates and returns a new dentry instantiated with the passed in inode. |
|
On failure NULL is returned and the passed in inode is dropped so the reference |
|
to inode is consumed in all cases and failure handling need not do any cleanup |
|
for the inode. If d_make_root(inode) is passed a NULL inode it returns NULL |
|
and also requires no further error handling. Typical usage is:: |
|
|
|
inode = foofs_new_inode(....); |
|
s->s_root = d_make_root(inode); |
|
if (!s->s_root) |
|
/* Nothing needed for the inode cleanup */ |
|
return -ENOMEM; |
|
... |
|
|
|
--- |
|
|
|
**mandatory** |
|
|
|
The witch is dead! Well, 2/3 of it, anyway. ->d_revalidate() and |
|
->lookup() do *not* take struct nameidata anymore; just the flags. |
|
|
|
--- |
|
|
|
**mandatory** |
|
|
|
->create() doesn't take ``struct nameidata *``; unlike the previous |
|
two, it gets "is it an O_EXCL or equivalent?" boolean argument. Note that |
|
local filesystems can ignore tha argument - they are guaranteed that the |
|
object doesn't exist. It's remote/distributed ones that might care... |
|
|
|
--- |
|
|
|
**mandatory** |
|
|
|
FS_REVAL_DOT is gone; if you used to have it, add ->d_weak_revalidate() |
|
in your dentry operations instead. |
|
|
|
--- |
|
|
|
**mandatory** |
|
|
|
vfs_readdir() is gone; switch to iterate_dir() instead |
|
|
|
--- |
|
|
|
**mandatory** |
|
|
|
->readdir() is gone now; switch to ->iterate() |
|
|
|
**mandatory** |
|
|
|
vfs_follow_link has been removed. Filesystems must use nd_set_link |
|
from ->follow_link for normal symlinks, or nd_jump_link for magic |
|
/proc/<pid> style links. |
|
|
|
--- |
|
|
|
**mandatory** |
|
|
|
iget5_locked()/ilookup5()/ilookup5_nowait() test() callback used to be |
|
called with both ->i_lock and inode_hash_lock held; the former is *not* |
|
taken anymore, so verify that your callbacks do not rely on it (none |
|
of the in-tree instances did). inode_hash_lock is still held, |
|
of course, so they are still serialized wrt removal from inode hash, |
|
as well as wrt set() callback of iget5_locked(). |
|
|
|
--- |
|
|
|
**mandatory** |
|
|
|
d_materialise_unique() is gone; d_splice_alias() does everything you |
|
need now. Remember that they have opposite orders of arguments ;-/ |
|
|
|
--- |
|
|
|
**mandatory** |
|
|
|
f_dentry is gone; use f_path.dentry, or, better yet, see if you can avoid |
|
it entirely. |
|
|
|
--- |
|
|
|
**mandatory** |
|
|
|
never call ->read() and ->write() directly; use __vfs_{read,write} or |
|
wrappers; instead of checking for ->write or ->read being NULL, look for |
|
FMODE_CAN_{WRITE,READ} in file->f_mode. |
|
|
|
--- |
|
|
|
**mandatory** |
|
|
|
do _not_ use new_sync_{read,write} for ->read/->write; leave it NULL |
|
instead. |
|
|
|
--- |
|
|
|
**mandatory** |
|
->aio_read/->aio_write are gone. Use ->read_iter/->write_iter. |
|
|
|
--- |
|
|
|
**recommended** |
|
|
|
for embedded ("fast") symlinks just set inode->i_link to wherever the |
|
symlink body is and use simple_follow_link() as ->follow_link(). |
|
|
|
--- |
|
|
|
**mandatory** |
|
|
|
calling conventions for ->follow_link() have changed. Instead of returning |
|
cookie and using nd_set_link() to store the body to traverse, we return |
|
the body to traverse and store the cookie using explicit void ** argument. |
|
nameidata isn't passed at all - nd_jump_link() doesn't need it and |
|
nd_[gs]et_link() is gone. |
|
|
|
--- |
|
|
|
**mandatory** |
|
|
|
calling conventions for ->put_link() have changed. It gets inode instead of |
|
dentry, it does not get nameidata at all and it gets called only when cookie |
|
is non-NULL. Note that link body isn't available anymore, so if you need it, |
|
store it as cookie. |
|
|
|
--- |
|
|
|
**mandatory** |
|
|
|
any symlink that might use page_follow_link_light/page_put_link() must |
|
have inode_nohighmem(inode) called before anything might start playing with |
|
its pagecache. No highmem pages should end up in the pagecache of such |
|
symlinks. That includes any preseeding that might be done during symlink |
|
creation. __page_symlink() will honour the mapping gfp flags, so once |
|
you've done inode_nohighmem() it's safe to use, but if you allocate and |
|
insert the page manually, make sure to use the right gfp flags. |
|
|
|
--- |
|
|
|
**mandatory** |
|
|
|
->follow_link() is replaced with ->get_link(); same API, except that |
|
|
|
* ->get_link() gets inode as a separate argument |
|
* ->get_link() may be called in RCU mode - in that case NULL |
|
dentry is passed |
|
|
|
--- |
|
|
|
**mandatory** |
|
|
|
->get_link() gets struct delayed_call ``*done`` now, and should do |
|
set_delayed_call() where it used to set ``*cookie``. |
|
|
|
->put_link() is gone - just give the destructor to set_delayed_call() |
|
in ->get_link(). |
|
|
|
--- |
|
|
|
**mandatory** |
|
|
|
->getxattr() and xattr_handler.get() get dentry and inode passed separately. |
|
dentry might be yet to be attached to inode, so do _not_ use its ->d_inode |
|
in the instances. Rationale: !@#!@# security_d_instantiate() needs to be |
|
called before we attach dentry to inode. |
|
|
|
--- |
|
|
|
**mandatory** |
|
|
|
symlinks are no longer the only inodes that do *not* have i_bdev/i_cdev/ |
|
i_pipe/i_link union zeroed out at inode eviction. As the result, you can't |
|
assume that non-NULL value in ->i_nlink at ->destroy_inode() implies that |
|
it's a symlink. Checking ->i_mode is really needed now. In-tree we had |
|
to fix shmem_destroy_callback() that used to take that kind of shortcut; |
|
watch out, since that shortcut is no longer valid. |
|
|
|
--- |
|
|
|
**mandatory** |
|
|
|
->i_mutex is replaced with ->i_rwsem now. inode_lock() et.al. work as |
|
they used to - they just take it exclusive. However, ->lookup() may be |
|
called with parent locked shared. Its instances must not |
|
|
|
* use d_instantiate) and d_rehash() separately - use d_add() or |
|
d_splice_alias() instead. |
|
* use d_rehash() alone - call d_add(new_dentry, NULL) instead. |
|
* in the unlikely case when (read-only) access to filesystem |
|
data structures needs exclusion for some reason, arrange it |
|
yourself. None of the in-tree filesystems needed that. |
|
* rely on ->d_parent and ->d_name not changing after dentry has |
|
been fed to d_add() or d_splice_alias(). Again, none of the |
|
in-tree instances relied upon that. |
|
|
|
We are guaranteed that lookups of the same name in the same directory |
|
will not happen in parallel ("same" in the sense of your ->d_compare()). |
|
Lookups on different names in the same directory can and do happen in |
|
parallel now. |
|
|
|
--- |
|
|
|
**recommended** |
|
|
|
->iterate_shared() is added; it's a parallel variant of ->iterate(). |
|
Exclusion on struct file level is still provided (as well as that |
|
between it and lseek on the same struct file), but if your directory |
|
has been opened several times, you can get these called in parallel. |
|
Exclusion between that method and all directory-modifying ones is |
|
still provided, of course. |
|
|
|
Often enough ->iterate() can serve as ->iterate_shared() without any |
|
changes - it is a read-only operation, after all. If you have any |
|
per-inode or per-dentry in-core data structures modified by ->iterate(), |
|
you might need something to serialize the access to them. If you |
|
do dcache pre-seeding, you'll need to switch to d_alloc_parallel() for |
|
that; look for in-tree examples. |
|
|
|
Old method is only used if the new one is absent; eventually it will |
|
be removed. Switch while you still can; the old one won't stay. |
|
|
|
--- |
|
|
|
**mandatory** |
|
|
|
->atomic_open() calls without O_CREAT may happen in parallel. |
|
|
|
--- |
|
|
|
**mandatory** |
|
|
|
->setxattr() and xattr_handler.set() get dentry and inode passed separately. |
|
The xattr_handler.set() gets passed the user namespace of the mount the inode |
|
is seen from so filesystems can idmap the i_uid and i_gid accordingly. |
|
dentry might be yet to be attached to inode, so do _not_ use its ->d_inode |
|
in the instances. Rationale: !@#!@# security_d_instantiate() needs to be |
|
called before we attach dentry to inode and !@#!@##!@$!$#!@#$!@$!@$ smack |
|
->d_instantiate() uses not just ->getxattr() but ->setxattr() as well. |
|
|
|
--- |
|
|
|
**mandatory** |
|
|
|
->d_compare() doesn't get parent as a separate argument anymore. If you |
|
used it for finding the struct super_block involved, dentry->d_sb will |
|
work just as well; if it's something more complicated, use dentry->d_parent. |
|
Just be careful not to assume that fetching it more than once will yield |
|
the same value - in RCU mode it could change under you. |
|
|
|
--- |
|
|
|
**mandatory** |
|
|
|
->rename() has an added flags argument. Any flags not handled by the |
|
filesystem should result in EINVAL being returned. |
|
|
|
--- |
|
|
|
|
|
**recommended** |
|
|
|
->readlink is optional for symlinks. Don't set, unless filesystem needs |
|
to fake something for readlink(2). |
|
|
|
--- |
|
|
|
**mandatory** |
|
|
|
->getattr() is now passed a struct path rather than a vfsmount and |
|
dentry separately, and it now has request_mask and query_flags arguments |
|
to specify the fields and sync type requested by statx. Filesystems not |
|
supporting any statx-specific features may ignore the new arguments. |
|
|
|
--- |
|
|
|
**mandatory** |
|
|
|
->atomic_open() calling conventions have changed. Gone is ``int *opened``, |
|
along with FILE_OPENED/FILE_CREATED. In place of those we have |
|
FMODE_OPENED/FMODE_CREATED, set in file->f_mode. Additionally, return |
|
value for 'called finish_no_open(), open it yourself' case has become |
|
0, not 1. Since finish_no_open() itself is returning 0 now, that part |
|
does not need any changes in ->atomic_open() instances. |
|
|
|
--- |
|
|
|
**mandatory** |
|
|
|
alloc_file() has become static now; two wrappers are to be used instead. |
|
alloc_file_pseudo(inode, vfsmount, name, flags, ops) is for the cases |
|
when dentry needs to be created; that's the majority of old alloc_file() |
|
users. Calling conventions: on success a reference to new struct file |
|
is returned and callers reference to inode is subsumed by that. On |
|
failure, ERR_PTR() is returned and no caller's references are affected, |
|
so the caller needs to drop the inode reference it held. |
|
alloc_file_clone(file, flags, ops) does not affect any caller's references. |
|
On success you get a new struct file sharing the mount/dentry with the |
|
original, on failure - ERR_PTR(). |
|
|
|
--- |
|
|
|
**mandatory** |
|
|
|
->clone_file_range() and ->dedupe_file_range have been replaced with |
|
->remap_file_range(). See Documentation/filesystems/vfs.rst for more |
|
information. |
|
|
|
--- |
|
|
|
**recommended** |
|
|
|
->lookup() instances doing an equivalent of:: |
|
|
|
if (IS_ERR(inode)) |
|
return ERR_CAST(inode); |
|
return d_splice_alias(inode, dentry); |
|
|
|
don't need to bother with the check - d_splice_alias() will do the |
|
right thing when given ERR_PTR(...) as inode. Moreover, passing NULL |
|
inode to d_splice_alias() will also do the right thing (equivalent of |
|
d_add(dentry, NULL); return NULL;), so that kind of special cases |
|
also doesn't need a separate treatment. |
|
|
|
--- |
|
|
|
**strongly recommended** |
|
|
|
take the RCU-delayed parts of ->destroy_inode() into a new method - |
|
->free_inode(). If ->destroy_inode() becomes empty - all the better, |
|
just get rid of it. Synchronous work (e.g. the stuff that can't |
|
be done from an RCU callback, or any WARN_ON() where we want the |
|
stack trace) *might* be movable to ->evict_inode(); however, |
|
that goes only for the things that are not needed to balance something |
|
done by ->alloc_inode(). IOW, if it's cleaning up the stuff that |
|
might have accumulated over the life of in-core inode, ->evict_inode() |
|
might be a fit. |
|
|
|
Rules for inode destruction: |
|
|
|
* if ->destroy_inode() is non-NULL, it gets called |
|
* if ->free_inode() is non-NULL, it gets scheduled by call_rcu() |
|
* combination of NULL ->destroy_inode and NULL ->free_inode is |
|
treated as NULL/free_inode_nonrcu, to preserve the compatibility. |
|
|
|
Note that the callback (be it via ->free_inode() or explicit call_rcu() |
|
in ->destroy_inode()) is *NOT* ordered wrt superblock destruction; |
|
as the matter of fact, the superblock and all associated structures |
|
might be already gone. The filesystem driver is guaranteed to be still |
|
there, but that's it. Freeing memory in the callback is fine; doing |
|
more than that is possible, but requires a lot of care and is best |
|
avoided. |
|
|
|
--- |
|
|
|
**mandatory** |
|
|
|
DCACHE_RCUACCESS is gone; having an RCU delay on dentry freeing is the |
|
default. DCACHE_NORCU opts out, and only d_alloc_pseudo() has any |
|
business doing so. |
|
|
|
--- |
|
|
|
**mandatory** |
|
|
|
d_alloc_pseudo() is internal-only; uses outside of alloc_file_pseudo() are |
|
very suspect (and won't work in modules). Such uses are very likely to |
|
be misspelled d_alloc_anon(). |
|
|
|
--- |
|
|
|
**mandatory** |
|
|
|
[should've been added in 2016] stale comment in finish_open() nonwithstanding, |
|
failure exits in ->atomic_open() instances should *NOT* fput() the file, |
|
no matter what. Everything is handled by the caller. |
|
|
|
--- |
|
|
|
**mandatory** |
|
|
|
clone_private_mount() returns a longterm mount now, so the proper destructor of |
|
its result is kern_unmount() or kern_unmount_array(). |
|
|
|
--- |
|
|
|
**mandatory** |
|
|
|
zero-length bvec segments are disallowed, they must be filtered out before |
|
passed on to an iterator. |
|
|
|
--- |
|
|
|
**mandatory** |
|
|
|
For bvec based itererators bio_iov_iter_get_pages() now doesn't copy bvecs but |
|
uses the one provided. Anyone issuing kiocb-I/O should ensure that the bvec and |
|
page references stay until I/O has completed, i.e. until ->ki_complete() has |
|
been called or returned with non -EIOCBQUEUED code. |
|
|
|
--- |
|
|
|
**mandatory** |
|
|
|
mnt_want_write_file() can now only be paired with mnt_drop_write_file(), |
|
whereas previously it could be paired with mnt_drop_write() as well. |
|
|
|
--- |
|
|
|
**mandatory** |
|
|
|
iov_iter_copy_from_user_atomic() is gone; use copy_page_from_iter_atomic(). |
|
The difference is copy_page_from_iter_atomic() advances the iterator and |
|
you don't need iov_iter_advance() after it. However, if you decide to use |
|
only a part of obtained data, you should do iov_iter_revert(). |
|
|
|
--- |
|
|
|
**mandatory** |
|
|
|
Calling conventions for file_open_root() changed; now it takes struct path * |
|
instead of passing mount and dentry separately. For callers that used to |
|
pass <mnt, mnt->mnt_root> pair (i.e. the root of given mount), a new helper |
|
is provided - file_open_root_mnt(). In-tree users adjusted.
|
|
|