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build_path_from_dentry() open-codes dentry_path_raw(). The reason we can't use dentry_path_raw() in there (and postprocess the result as needed) is that the callers of build_path_from_dentry() expect that the object to be freed on cleanup and the string to be used are at the same address. That's painful, since the path is naturally built end-to-beginning - we start at the leaf and go through the ancestors, accumulating the pathname. Life would be easier if we left the buffer allocation to callers. It wouldn't be exact-sized buffer, but none of the callers keep the result for long - it's always freed before the caller returns. So there's no need to do exact-sized allocation; better use __getname()/__putname(), same as we do for pathname arguments of syscalls. What's more, there's no need to do allocation under spinlocks, so GFP_ATOMIC is not needed. Next patch will replace the open-coded dentry_path_raw() (in build_path_from_dentry_optional_prefix()) with calling the real thing. This patch only introduces wrappers for allocating/freeing the buffers and switches to new calling conventions: build_path_from_dentry(dentry, buf) expects buf to be address of a page-sized object or NULL, return value is a pathname built inside that buffer on success, ERR_PTR(-ENOMEM) if buf is NULL and ERR_PTR(-ENAMETOOLONG) if the pathname won't fit into page. Note that we don't need to check for failure when allocating the buffer in the caller - build_path_from_dentry() will do the right thing. Signed-off-by: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: Steve French <stfrench@microsoft.com>
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.