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125 lines
4.2 KiB
C
125 lines
4.2 KiB
C
// SPDX-License-Identifier: GPL-3.0-or-later
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// Copyright (C) 2011 Andrea Mazzoleni
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#ifndef __UNIX_H
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#define __UNIX_H
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#ifdef __linux__
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#define HAVE_LINUX_DEVICE 1 /**< In Linux enables special device support. */
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#define HAVE_DIRECT_IO 1 /**< Support O_DIRECT in open(). */
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#endif
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#define O_BINARY 0 /**< Not used in Unix. */
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#define O_SEQUENTIAL 0 /**< In Unix posix_fadvise() shall be used. */
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/**
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* If nanoseconds are not supported, we report the special STAT_NSEC_INVALID value,
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* to mark that it's undefined.
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*/
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#define STAT_NSEC_INVALID -1
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/* Check if we have nanoseconds support */
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#if HAVE_STRUCT_STAT_ST_MTIM_TV_NSEC
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#define STAT_NSEC(st) ((int)(st)->st_mtim.tv_nsec) /* Linux */
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#elif HAVE_STRUCT_STAT_ST_MTIMENSEC
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#define STAT_NSEC(st) ((int)(st)->st_mtimensec) /* NetBSD */
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#elif HAVE_STRUCT_STAT_ST_MTIMESPEC_TV_NSEC
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#define STAT_NSEC(st) ((int)(st)->st_mtimespec.tv_nsec) /* FreeBSD, Mac OS X */
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#else
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#define STAT_NSEC(st) STAT_NSEC_INVALID
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#endif
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#if HAVE_POSIX_FADVISE
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/**
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* Wrapper around posix_fadvise() that handles ENOENT by converting it to
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* ENOSYS.
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*
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* Why can posix_fadvise() return ENOENT?
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*
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* According to POSIX and the Linux kernel's standard fadvise64 implementation
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* (mm/fadvise.c), posix_fadvise() should only return EBADF (bad file
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* descriptor), ESPIPE (fd refers to a pipe or FIFO), or EINVAL (invalid
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* advice value or arguments). ENOENT is never generated by the kernel's
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* generic path.
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*
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* However, the VFS layer allows individual filesystems to provide their own
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* .fadvise() method, which is called instead of (or in addition to) the
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* generic implementation. Certain filesystem drivers can return ENOENT in
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* this method for reasons that are completely unrelated to the file not
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* existing (the file is clearly open, we have a valid fd):
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*
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* - NFS: A stale NFS inode can be revalidated against the server while
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* fadvise is being processed. If the server-side file has been removed or
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* renamed, the revalidation discovers the inode is gone and returns
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* -ENOENT, even though the client still holds an open file descriptor.
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*
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* - FUSE-based filesystems (mergerfs, sshfs, rclone, etc.): The FUSE daemon
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* receives the fadvise request and may forward it to an underlying backend.
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* If that backend cannot find the file (e.g., the backing path has changed,
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* the FUSE daemon is partially initialised, or the daemon translates the
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* request and the target layer returns an error), the daemon may return
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* ENOENT to the kernel.
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*
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* - Overlayfs (used by Docker, Podman, LXC): The overlayfs .fadvise()
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* implementation delegates to the lower or upper layer. If the lookup
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* through the overlay stack fails to find the real inode (e.g., the upper
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* directory entry is absent and the lower copy is in a weird state), the
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* delegation can return ENOENT.
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*
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* - Other network or virtual filesystems: Any out-of-tree or in-tree
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* filesystem that implements .fadvise() and performs a path or inode
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* lookup as part of processing the hint can propagate ENOENT if that
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* internal lookup fails.
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*
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* Because posix_fadvise() is always an advisory hint, it never affects
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* correctness, only performance, it is safe to treat unexpected errors,
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* including ENOENT, as "not supported" (ENOSYS) and continue.
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*/
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int posix_fadvise_wrapper(int fd, off_t offset, off_t len, int advice);
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#endif
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#if !HAVE_EACCESS
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/**
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* Check effective user's permissions for a file.
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* Conceptually identical to access(), but uses the effective UID/GID.
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*/
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int eaccess(const char* pathname, int mode);
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#endif
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/**
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* Open a file with the O_NOATIME flag to avoid to update the access time.
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*/
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int open_noatime(const char* file, int flags);
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/**
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* Check if the specified file is hidden.
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*/
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int dirent_hidden(struct dirent* dd);
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/**
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* Return a description of the file type.
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*/
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const char* stat_desc(struct stat* st);
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/**
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* Return the alignment requirement for direct IO.
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*/
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size_t direct_size(void);
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/****************************************************************************/
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/* thread */
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#if HAVE_PTHREAD_H
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#include <pthread.h>
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#endif
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#if HAVE_PTHREAD
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#define HAVE_THREAD 1
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typedef pthread_t thread_id_t;
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typedef pthread_mutex_t thread_mutex_t;
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typedef pthread_cond_t thread_cond_t;
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typedef pthread_key_t thread_key_t;
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#endif
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#endif
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