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
  22 static inline void close_preserve_errno(int fd)
  23 {
  24     int serrno = errno;
  25     close(fd);
  26     errno = serrno;
  27 }
  28
  29 static 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
  35 static inline int openat_file(int dirfd, const char *name, int flags,
  36                               mode_t mode)
  37 {
  38     int fd, serrno, ret;
  39
  40 again:
  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
  72 ssize_t fgetxattrat_nofollow(int dirfd, const char *path, const char *name,
  73                              void *value, size_t size);
  74 int fsetxattrat_nofollow(int dirfd, const char *path, const char *name,
  75                          void *value, size_t size, int flags);
  76 ssize_t flistxattrat_nofollow(int dirfd, const char *filename,
  77                               char *list, size_t size);
  78 ssize_t fremovexattrat_nofollow(int dirfd, const char *filename,
  79                                 const char *name);
  80
  81 #endif