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update Documentation/filesystems/ regarding the follow_link/put_link changes

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Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro 2015-05-11 08:29:30 -04:00
parent 8f47a0167c
commit 203bc643db
2 changed files with 27 additions and 8 deletions
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17
Documentation/filesystems/porting
View File

@ -483,3 +483,20 @@ in your dentry operations 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.

18
Documentation/filesystems/vfs.txt
View File

@ -436,16 +436,18 @@ otherwise noted.
follow_link: called by the VFS to follow a symbolic link to the
inode it points to. Only required if you want to support
symbolic links. This method returns a void pointer cookie
that is passed to put_link().
symbolic links. This method returns the symlink body
to traverse (and possibly resets the current position with
nd_jump_link()). If the body won't go away until the inode
is gone, nothing else is needed; if it needs to be otherwise
pinned, the data needed to release whatever we'd grabbed
is to be stored in void * variable passed by address to
follow_link() instance.
put_link: called by the VFS to release resources allocated by
follow_link(). The cookie returned by follow_link() is passed
to this method as the last parameter. It is used by
filesystems such as NFS where page cache is not stable
(i.e. page that was installed when the symbolic link walk
started might not be in the page cache at the end of the
walk).
follow_link(). The cookie stored by follow_link() is passed
to this method as the last parameter; only called when
cookie isn't NULL.
permission: called by the VFS to check for access rights on a POSIX-like
filesystem.