treefiles.c

   1 #include <fcntl.h>
   2 #include <inttypes.h>
   3 #include <stdio.h>
   4 #include <unistd.h>
   5 #include <sys/stat.h>
   6 #include <sys/types.h>
   7
   8 #include <glib.h>
   9
  10 #include <backend.h>
  11 #include <config.h>
  12 #include <cliserv.h>
  13 #include <treefiles.h>
  14 #include <nbd-debug.h>
  15 #include <nbdsrv.h>
  16 /**
  17  * Tree structure helper functions
  18  */
  19 void construct_path(char* name,int lenmax,off_t size, off_t pos, off_t * ppos) {
  20         if (lenmax<10)
  21                 err("Char buffer overflow. This is likely a bug.");
  22
  23         if (size<TREEDIRSIZE*TREEPAGESIZE) {
  24                 // we are done, add filename
  25                 snprintf(name,lenmax,"/FILE%04" PRIX64,(pos/TREEPAGESIZE) % TREEDIRSIZE);
  26                 *ppos = pos / (TREEPAGESIZE*TREEDIRSIZE);
  27         } else {
  28                 construct_path(name+9,lenmax-9,size/TREEDIRSIZE,pos,ppos);
  29                 char buffer[10];
  30                 snprintf(buffer,sizeof(buffer),"/TREE%04jX",(intmax_t)(*ppos % TREEDIRSIZE));
  31                 memcpy(name,buffer,9); // copy into string without trailing zero
  32                 *ppos/=TREEDIRSIZE;
  33         }
  34 }
  35
  36 void delete_treefile(char* name,off_t size,off_t pos) {
  37         char filename[256+strlen(name)];
  38         strcpy(filename,name);
  39         off_t ppos;
  40         construct_path(filename+strlen(name),256,size,pos,&ppos);
  41
  42         DEBUG("Deleting treefile: %s",filename);
  43
  44         if (unlink(filename)==-1)
  45                 DEBUG("Deleting failed : %s",strerror(errno));
  46 }
  47
  48 void mkdir_path(char * path) {
  49         char *subpath=path+1;
  50         while ((subpath=strchr(subpath,'/'))) {
  51                 *subpath='\0'; // path is modified in place with terminating null char instead of slash
  52                 if (mkdir(path,0700)==-1) {
  53                         if (errno!=EEXIST)
  54                                 err("Path access error! %m");
  55                 }
  56                 *subpath='/';
  57                 subpath++;
  58         }
  59 }
  60
  61 int open_treefile(char* name,mode_t mode,off_t size,off_t pos) {
  62         char filename[256+strlen(name)];
  63         strcpy(filename,name);
  64         off_t ppos;
  65         construct_path(filename+strlen(name),256,size,pos,&ppos);
  66
  67         DEBUG("Accessing treefile %s ( offset %llu of %llu)",filename,(unsigned long long)pos,(unsigned long long)size);
  68
  69         int handle=open(filename, mode, 0600);
  70         if (handle<0 && errno==ENOENT) {
  71                 if (mode & O_RDWR) {
  72
  73                         DEBUG("Creating new treepath");
  74
  75                         mkdir_path(filename);
  76                         handle=open(filename, O_RDWR|O_CREAT, 0600);
  77                         if (handle<0) {
  78                                 err("Error opening tree block file %m");
  79                         }
  80                 } else {
  81
  82                         DEBUG("Creating a dummy tempfile for reading");
  83                         gchar * tmpname;
  84                         tmpname = g_strdup_printf("dummy-XXXXXX");
  85                         handle = mkstemp(tmpname);
  86                         if (handle>0) {
  87                                 unlink(tmpname); /* File will stick around whilst FD open */
  88                         } else {
  89                                 err("Error opening tree block file %m");
  90                         }
  91                         g_free(tmpname);
  92                 }
  93                 char *n = "\0";
  94                 myseek(handle,TREEPAGESIZE-1);
  95                 ssize_t c = write(handle,n,1);
  96                 if (c<1) {
  97                         err("Error setting tree block file size %m");
  98                 }
  99         }
 100         return handle;
 101 }
 102