Commit ef4aa53f authored by Fox Chen's avatar Fox Chen Committed by Jonathan Corbet
Browse files

docs: path-lookup: update symlink description 



instead of lookup_real()/vfs_create(), i_op->lookup() and
i_op->create() will be called directly.

update vfs_open() logic

should_follow_link is merged into lookup_last() or open_last_lookup()
which returns symlink name instead of an integer.

Signed-off-by: default avatarFox Chen <foxhlchen@gmail.com>
Reviewed-by: default avatarNeilBrown <neilb@suse.de>
Link: https://lore.kernel.org/r/20210527091618.287093-13-foxhlchen@gmail.com


Signed-off-by: default avatarJonathan Corbet <corbet@lwn.net>
parent 3c1be84b

Documentation/filesystems/path-lookup.rst

+6 −7
Original line number Diff line number Diff line
@@ -1200,16 +1200,15 @@ the code. 
   it.  If the file was found in the dcache, then ``vfs_open()`` is used for

   this.  If not, then ``lookup_open()`` will either call ``atomic_open()`` (if

   the filesystem provides it) to combine the final lookup with the open, or

   will perform the separate ``lookup_real()`` and ``vfs_create()`` steps

   will perform the separate ``i_op->lookup()`` and ``i_op->create()`` steps

   directly.  In the later case the actual "open" of this newly found or

   created file will be performed by ``vfs_open()``, just as if the name

   were found in the dcache.



2. ``vfs_open()`` can fail with ``-EOPENSTALE`` if the cached information

   wasn't quite current enough.  Rather than restarting the lookup from

   the top with ``LOOKUP_REVAL`` set, ``lookup_open()`` is called instead,

   giving the filesystem a chance to resolve small inconsistencies.

   If that doesn't work, only then is the lookup restarted from the top.

   wasn't quite current enough.  If it's in RCU-walk ``-ECHILD`` will be returned

   otherwise ``-ESTALE`` is returned.  When ``-ESTALE`` is returned, the caller may

   retry with ``LOOKUP_REVAL`` flag set.



3. An open with O_CREAT **does** follow a symlink in the final component,

   unlike other creation system calls (like ``mkdir``).  So the sequence::
@@ -1219,8 +1218,8 @@ the code. 


   will create a file called ``/tmp/bar``.  This is not permitted if

   ``O_EXCL`` is set but otherwise is handled for an O_CREAT open much

   like for a non-creating open: ``should_follow_link()`` returns ``1``, and

   so does ``do_last()`` so that ``trailing_symlink()`` gets called and the

   like for a non-creating open: ``lookup_last()`` or ``open_last_lookup()``

   returns a non ``NULL`` value, and ``link_path_walk()`` gets called and the

   open process continues on the symlink that was found.



Updating the access time