treefiles.c

   1 #include "lfs.h"
   2 #include <fcntl.h>
   3 #include <inttypes.h>
   4 #include <stdio.h>
   5 #include <unistd.h>
   6 #include <sys/stat.h>
   7 #include <sys/types.h>
   8
   9 #include <glib.h>
  10
  11 #include <backend.h>
  12 #include <config.h>
  13 #include <cliserv.h>
  14 #include <treefiles.h>
  15 #include <nbd-debug.h>
  16 #include <nbdsrv.h>
  17 /**
  18  * Tree structure helper functions
  19  */
  20 void construct_path(char* name,int lenmax,off_t size, off_t pos, off_t * ppos) {
  21         if (lenmax<10)
  22                 err("Char buffer overflow. This is likely a bug.");
  23
  24         if (size<TREEDIRSIZE*TREEPAGESIZE) {
  25                 // we are done, add filename
  26                 snprintf(name,lenmax,"/FILE%04" PRIX64,(pos/TREEPAGESIZE) % TREEDIRSIZE);
  27                 *ppos = pos / (TREEPAGESIZE*TREEDIRSIZE);
  28         } else {
  29                 construct_path(name+9,lenmax-9,size/TREEDIRSIZE,pos,ppos);
  30                 char buffer[10];
  31                 snprintf(buffer,sizeof(buffer),"/TREE%04jX",(intmax_t)(*ppos % TREEDIRSIZE));
  32                 memcpy(name,buffer,9); // copy into string without trailing zero
  33                 *ppos/=TREEDIRSIZE;
  34         }
  35 }
  36
  37 void delete_treefile(char* name,off_t size,off_t pos) {
  38         char filename[PATH_MAX];
  39         off_t ppos;
  40
  41         strncpy(filename,name,PATH_MAX-1);
  42         filename[PATH_MAX-1] = '\0';
  43         construct_path(filename+strlen(name),PATH_MAX-strlen(name)-1,size,pos,&ppos);
  44
  45         DEBUG("Deleting treefile: %s",filename);
  46
  47         if (unlink(filename)==-1)
  48                 DEBUG("Deleting failed : %s",strerror(errno));
  49 }
  50
  51 void mkdir_path(char * path) {
  52         char *subpath=path+1;
  53         while ((subpath=strchr(subpath,'/'))) {
  54                 *subpath='\0'; // path is modified in place with terminating null char instead of slash
  55                 if (mkdir(path,0700)==-1) {
  56                         if (errno!=EEXIST)
  57                                 err("Path access error! %m");
  58                 }
  59                 *subpath='/';
  60                 subpath++;
  61         }
  62 }
  63
  64 int open_treefile(char* name,mode_t mode,off_t size,off_t pos, pthread_mutex_t *mutex) {
  65         char filename[PATH_MAX];
  66         off_t ppos;
  67
  68         strncpy(filename,name,PATH_MAX-1);
  69         filename[PATH_MAX - 1] = '\0';
  70         construct_path(filename+strlen(name),PATH_MAX-strlen(name)-1,size,pos,&ppos);
  71
  72         DEBUG("Accessing treefile %s ( offset %llu of %llu)",filename,(unsigned long long)pos,(unsigned long long)size);
  73
  74         pthread_mutex_lock(mutex);
  75         int handle=open(filename, mode, 0600);
  76         if (handle<0 && errno==ENOENT) {
  77                 if (mode & O_RDWR) {
  78
  79                         DEBUG("Creating new treepath");
  80
  81                         mkdir_path(filename);
  82                         handle=open(filename, O_RDWR|O_CREAT, 0600);
  83                         if (handle<0) {
  84                                 err("Error opening tree block file %m");
  85                         }
  86                 } else {
  87
  88                         DEBUG("Creating a dummy tempfile for reading");
  89                         gchar * tmpname;
  90                         tmpname = g_strdup_printf("dummy-XXXXXX");
  91                         mode_t oldmode = umask(77);
  92                         handle = mkstemp(tmpname);
  93                         umask(oldmode);
  94                         if (handle>0) {
  95                                 unlink(tmpname); /* File will stick around whilst FD open */
  96                         } else {
  97                                 err("Error opening tree block file %m");
  98                         }
  99                         g_free(tmpname);
 100                 }
 101                 char *n = "\0";
 102                 if(lseek(handle,TREEPAGESIZE-1, SEEK_SET) < 0) {
 103                         err("Could not create tree file!\n");
 104                 }
 105                 ssize_t c = write(handle,n,1);
 106                 if (c<1) {
 107                         err("Error setting tree block file size %m");
 108                 }
 109         }
 110         pthread_mutex_unlock(mutex);
 111         return handle;
 112 }
 113