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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: Fox Chen <foxhlchen@gmail.com>
Reviewed-by: NeilBrown <neilb@suse.de>
Link: https://lore.kernel.org/r/20210527091618.287093-13-foxhlchen@gmail.com
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
This commit is contained in:
Fox Chen 2021-05-27 17:16:17 +08:00 committed by Jonathan Corbet
parent 3c1be84b8d
commit ef4aa53f36
1 changed files with 6 additions and 7 deletions
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13
Documentation/filesystems/path-lookup.rst
View File

@ -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