LXR qemu/hw/9pfs/9p-util.h

   1/*
   2 * 9p utilities
   3 *
   4 * Copyright IBM, Corp. 2017
   5 *
   6 * Authors:
   7 *  Greg Kurz <groug@kaod.org>
   8 *
   9 * This work is licensed under the terms of the GNU GPL, version 2 or later.
  10 * See the COPYING file in the top-level directory.
  11 */
  12
  13#ifndef QEMU_9P_UTIL_H
  14#define QEMU_9P_UTIL_H
  15
  16#ifdef O_PATH
  17#define O_PATH_9P_UTIL O_PATH
  18#else
  19#define O_PATH_9P_UTIL 0
  20#endif
  21
  22static inline void close_preserve_errno(int fd)
  23{
  24    int serrno = errno;
  25    close(fd);
  26    errno = serrno;
  27}
  28
  29static inline int openat_dir(int dirfd, const char *name)
  30{
  31    return openat(dirfd, name,
  32                  O_DIRECTORY | O_RDONLY | O_NOFOLLOW | O_PATH_9P_UTIL);
  33}
  34
  35static inline int openat_file(int dirfd, const char *name, int flags,
  36                              mode_t mode)
  37{
  38    int fd, serrno, ret;
  39
  40again:
  41    fd = openat(dirfd, name, flags | O_NOFOLLOW | O_NOCTTY | O_NONBLOCK,
  42                mode);
  43    if (fd == -1) {
  44        if (errno == EPERM && (flags & O_NOATIME)) {
  45            /*
  46             * The client passed O_NOATIME but we lack permissions to honor it.
  47             * Rather than failing the open, fall back without O_NOATIME. This
  48             * doesn't break the semantics on the client side, as the Linux
  49             * open(2) man page notes that O_NOATIME "may not be effective on
  50             * all filesystems". In particular, NFS and other network
  51             * filesystems ignore it entirely.
  52             */
  53            flags &= ~O_NOATIME;
  54            goto again;
  55        }
  56        return -1;
  57    }
  58
  59    serrno = errno;
  60    /* O_NONBLOCK was only needed to open the file. Let's drop it. We don't
  61     * do that with O_PATH since fcntl(F_SETFL) isn't supported, and openat()
  62     * ignored it anyway.
  63     */
  64    if (!(flags & O_PATH_9P_UTIL)) {
  65        ret = fcntl(fd, F_SETFL, flags);
  66        assert(!ret);
  67    }
  68    errno = serrno;
  69    return fd;
  70}
  71
  72ssize_t fgetxattrat_nofollow(int dirfd, const char *path, const char *name,
  73                             void *value, size_t size);
  74int fsetxattrat_nofollow(int dirfd, const char *path, const char *name,
  75                         void *value, size_t size, int flags);
  76ssize_t flistxattrat_nofollow(int dirfd, const char *filename,
  77                              char *list, size_t size);
  78ssize_t fremovexattrat_nofollow(int dirfd, const char *filename,
  79                                const char *name);
  80
  81#endif
  82