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We use nd->stack to store two things: pinning down the symlinks we are resolving and resuming the name traversal when a nested symlink is finished. Currently, nd->depth is used to keep track of both. It's 0 when we call link_path_walk() for the first time (for the pathname itself) and 1 on all subsequent calls (for trailing symlinks, if any). That's fine, as far as pinning symlinks goes - when handling a trailing symlink, the string we are interpreting is the body of symlink pinned down in nd->stack[0]. It's rather inconvenient with respect to handling nested symlinks, though - when we run out of a string we are currently interpreting, we need to decide whether it's a nested symlink (in which case we need to pick the string saved back when we started to interpret that nested symlink and resume its traversal) or not (in which case we are done with link_path_walk()). Current solution is a bit of a kludge - in handling of trailing symlink (in lookup_last() and open_last_lookups() we clear nd->stack[0].name. That allows link_path_walk() to use the following rules when running out of a string to interpret: * if nd->depth is zero, we are at the end of pathname itself. * if nd->depth is positive, check the saved string; for nested symlink it will be non-NULL, for trailing symlink - NULL. It works, but it's rather non-obvious. Note that we have two sets: the set of symlinks currently being traversed and the set of postponed pathname tails. The former is stored in nd->stack[0..nd->depth-1].link and it's valid throught the pathname resolution; the latter is valid only during an individual call of link_path_walk() and it occupies nd->stack[0..nd->depth-1].name for the first call of link_path_walk() and nd->stack[1..nd->depth-1].name for subsequent ones. The kludge is basically a way to recognize the second set becoming empty. The things get simpler if we keep track of the second set's size explicitly and always store it in nd->stack[0..depth-1].name. We access the second set only inside link_path_walk(), so its size can live in a local variable; that way the check becomes trivial without the need of that kludge. Signed-off-by: Al Viro <viro@zeniv.linux.org.uk> |
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| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| samples | ||
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| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
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| README | ||
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.