fs.c

   1 /*
   2  * Copyright (C) 2012-2020 all contributors <cmogstored-public@yhbt.net>
   3  * License: GPL-3.0+ <https://www.gnu.org/licenses/gpl-3.0.txt>
   4  *
   5  * All path operations we support are relative to mog_svc.docroot.
   6  * Absolute path lookups are sometimes more expensive, especially
   7  * for deeper directory structures, so we'll favor AT_FILE functions.
   8  *
   9  * However, it's somewhat common for systems to have AT_FILE functions
  10  * to be available on the system they're built on, but not available
  11  * on the system the code is deployed on.  We'll provide fallbacks to
  12  * the absolute path variants for everything.
  13  */
  14 #include "cmogstored.h"
  15 #define MY_PATHMAX 256
  16 #ifndef O_NOATIME
  17 # define O_NOATIME 0
  18 #endif
  19
  20 static int noatime_flags = O_RDONLY | O_NOATIME;
  21 static int put_flags = O_RDWR;
  22
  23 /*
  24  * Like AT_FILE functions, we may be built on systems with O_CLOEXEC and
  25  * run on systems without it.  O_CLOEXEC is still too recent and was
  26  * broken on some Linux kernels, so we always run cloexec_detect.c at
  27  * startup.
  28  */
  29 #ifdef O_CLOEXEC
  30 void mog_cloexec_works(void)
  31 {
  32         noatime_flags |= O_CLOEXEC;
  33         put_flags |= O_CLOEXEC;
  34 }
  35 #endif /* O_CLOEXEC */
  36
  37 /* we only use real *at syscalls, Gnulib workalikes aren't thread-safe */
  38
  39 #define GET_FSPATH(DST,SRC) do { \
  40         int rc = snprintf((DST), sizeof(DST), "%s%s", svc->docroot, (SRC)); \
  41         if (rc <= 0 || rc >= sizeof(DST)) { \
  42                 errno = ENAMETOOLONG; \
  43                 return -1; \
  44         } \
  45 } while (0)
  46
  47 #ifndef HAVE_FSTATAT
  48 int mog_stat(struct mog_svc *svc, const char *path, struct stat *sb)
  49 {
  50         char fspath[MY_PATHMAX];
  51
  52         GET_FSPATH(fspath, path);
  53         return stat(fspath, sb);
  54 }
  55 #endif /* !HAVE_FSTATAT */
  56
  57 #ifdef HAVE_OPENAT
  58 static int open_read(struct mog_svc *svc, const char *path)
  59 {
  60         return openat(svc->docroot_fd, path + 1, noatime_flags);
  61 }
  62
  63 int mog_open_put(struct mog_svc *svc, const char *path, int flags)
  64 {
  65         return openat(svc->docroot_fd, path + 1, flags | put_flags, 0600);
  66 }
  67 #else /* !HAVE_OPENAT */
  68 MOG_NOINLINE static int open_read(struct mog_svc *svc, const char *path)
  69 {
  70         char fspath[MY_PATHMAX];
  71
  72         GET_FSPATH(fspath, path);
  73         return open(fspath, noatime_flags);
  74 }
  75
  76 int mog_open_put(struct mog_svc *svc, const char *path, int flags)
  77 {
  78         char fspath[MY_PATHMAX];
  79
  80         GET_FSPATH(fspath, path);
  81         return open(fspath, flags | put_flags, 0600);
  82 }
  83 #endif /* !HAVE_OPENAT */
  84
  85 int mog_open_read(struct mog_svc *svc, const char *path)
  86 {
  87         int fd;
  88
  89 retry:
  90         fd = open_read(svc, path);
  91         if (fd < 0 && errno != ENOENT && (noatime_flags & O_NOATIME)) {
  92                 noatime_flags = O_RDONLY;
  93                 goto retry;
  94         }
  95         return fd;
  96 }
  97
  98 #ifndef HAVE_UNLINKAT
  99 int mog_unlink(struct mog_svc *svc, const char *path)
 100 {
 101         char fspath[MY_PATHMAX];
 102
 103         GET_FSPATH(fspath,path);
 104         return unlink(fspath);
 105 }
 106 #endif /* !HAVE_UNLINKAT */
 107
 108 #ifndef HAVE_RENAMEAT
 109 int mog_rename(struct mog_svc *svc, const char *old, const char *new)
 110 {
 111         char fsnew[MY_PATHMAX];
 112         char fsold[MY_PATHMAX];
 113
 114         GET_FSPATH(fsold, old);
 115         GET_FSPATH(fsnew, new);
 116         return rename(fsold, fsnew);
 117 }
 118 #endif /* !HAVE_RENAMEAT */
 119
 120 #ifndef HAVE_MKDIRAT
 121 int mog_mkdir(struct mog_svc *svc, const char *path, mode_t mode)
 122 {
 123         char fspath[MY_PATHMAX];
 124
 125         GET_FSPATH(fspath, path);
 126         return mkdir(fspath, mode);
 127 }
 128 #endif /* !HAVE_MKDIRAT */
 129
 130 int mog_statvfs(struct mog_svc *svc, struct mog_dev *dev, struct statvfs *v)
 131 {
 132         char fspath[MY_PATHMAX];
 133         int rc = snprintf(fspath, sizeof(fspath), "%s/dev%u",
 134                           svc->docroot, dev->devid);
 135
 136         if (rc <= 0) {
 137                 errno = ENAMETOOLONG;
 138                 return -1;
 139         }
 140         return statvfs(fspath, v);
 141 }