lib/fuse_kern_chan.c

   1 /*
   2     FUSE: Filesystem in Userspace
   3     Copyright (C) 2001-2006  Miklos Szeredi <miklos@szeredi.hu>
   4
   5     This program can be distributed under the terms of the GNU LGPL.
   6     See the file COPYING.LIB
   7 */
   8
   9 #include "fuse_lowlevel.h"
  10 #include "fuse_kernel.h"
  11
  12 #include <stdio.h>
  13 #include <errno.h>
  14 #include <unistd.h>
  15 #include <assert.h>
  16
  17 static int fuse_kern_chan_receive(struct fuse_chan **chp, char *buf,
  18                                   size_t size)
  19 {
  20     struct fuse_chan *ch = *chp;
  21     int err;
  22     ssize_t res;
  23     struct fuse_session *se = fuse_chan_session(ch);
  24     assert(se != NULL);
  25
  26  restart:
  27     res = read(fuse_chan_fd(ch), buf, size);
  28     err = errno;
  29
  30     if (fuse_session_exited(se))
  31         return 0;
  32     if (res == -1) {
  33         /* ENOENT means the operation was interrupted, it's safe
  34            to restart */
  35         if (err == ENOENT)
  36             goto restart;
  37
  38         /* Errors occuring during normal operation: EINTR (read
  39            interrupted), EAGAIN (nonblocking I/O), ENODEV (filesystem
  40            umounted) */
  41         if (err != EINTR && err != EAGAIN && err != ENODEV)
  42             perror("fuse: reading device");
  43         return -err;
  44     }
  45     if ((size_t) res < sizeof(struct fuse_in_header)) {
  46         fprintf(stderr, "short read on fuse device\n");
  47         return -EIO;
  48     }
  49     return res;
  50 }
  51
  52 static int fuse_kern_chan_send(struct fuse_chan *ch, const struct iovec iov[],
  53                                size_t count)
  54 {
  55     if (iov) {
  56         ssize_t res = writev(fuse_chan_fd(ch), iov, count);
  57         int err = errno;
  58
  59         if (res == -1) {
  60             struct fuse_session *se = fuse_chan_session(ch);
  61
  62             assert(se != NULL);
  63
  64             /* ENOENT means the operation was interrupted */
  65             if (!fuse_session_exited(se) && err != ENOENT)
  66                 perror("fuse: writing device");
  67             return -err;
  68         }
  69     }
  70     return 0;
  71 }
  72
  73 static void fuse_kern_chan_destroy(struct fuse_chan *ch)
  74 {
  75     close(fuse_chan_fd(ch));
  76 }
  77
  78 #define MIN_BUFSIZE 0x21000
  79
  80 struct fuse_chan *fuse_kern_chan_new(int fd)
  81 {
  82     struct fuse_chan_ops op = {
  83         .receive = fuse_kern_chan_receive,
  84         .send = fuse_kern_chan_send,
  85         .destroy = fuse_kern_chan_destroy,
  86     };
  87     size_t bufsize = getpagesize() + 0x1000;
  88     bufsize = bufsize < MIN_BUFSIZE ? MIN_BUFSIZE : bufsize;
  89     return fuse_chan_new(&op, fd, bufsize, NULL);
  90 }