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[256+strlen(name)];
  39         strcpy(filename,name);
  40         off_t ppos;
  41         construct_path(filename+strlen(name),256,size,pos,&ppos);
  42
  43         DEBUG("Deleting treefile: %s",filename);
  44
  45         if (unlink(filename)==-1)
  46                 DEBUG("Deleting failed : %s",strerror(errno));
  47 }
  48
  49 void mkdir_path(char * path) {
  50         char *subpath=path+1;
  51         while ((subpath=strchr(subpath,'/'))) {
  52                 *subpath='\0'; // path is modified in place with terminating null char instead of slash
  53                 if (mkdir(path,0700)==-1) {
  54                         if (errno!=EEXIST)
  55                                 err("Path access error! %m");
  56                 }
  57                 *subpath='/';
  58                 subpath++;
  59         }
  60 }
  61
  62 int open_treefile(char* name,mode_t mode,off_t size,off_t pos, pthread_mutex_t *mutex) {
  63         char filename[256+strlen(name)];
  64         strcpy(filename,name);
  65         off_t ppos;
  66         construct_path(filename+strlen(name),256,size,pos,&ppos);
  67
  68         DEBUG("Accessing treefile %s ( offset %llu of %llu)",filename,(unsigned long long)pos,(unsigned long long)size);
  69
  70         pthread_mutex_lock(mutex);
  71         int handle=open(filename, mode, 0600);
  72         if (handle<0 && errno==ENOENT) {
  73                 if (mode & O_RDWR) {
  74
  75                         DEBUG("Creating new treepath");
  76
  77                         mkdir_path(filename);
  78                         handle=open(filename, O_RDWR|O_CREAT, 0600);
  79                         if (handle<0) {
  80                                 err("Error opening tree block file %m");
  81                         }
  82                 } else {
  83
  84                         DEBUG("Creating a dummy tempfile for reading");
  85                         gchar * tmpname;
  86                         tmpname = g_strdup_printf("dummy-XXXXXX");
  87                         mode_t oldmode = umask(77);
  88                         handle = mkstemp(tmpname);
  89                         umask(oldmode);
  90                         if (handle>0) {
  91                                 unlink(tmpname); /* File will stick around whilst FD open */
  92                         } else {
  93                                 err("Error opening tree block file %m");
  94                         }
  95                         g_free(tmpname);
  96                 }
  97                 char *n = "\0";
  98                 if(lseek(handle,TREEPAGESIZE-1, SEEK_SET) < 0) {
  99                         err("Could not create tree file!\n");
 100                 }
 101                 ssize_t c = write(handle,n,1);
 102                 if (c<1) {
 103                         err("Error setting tree block file size %m");
 104                 }
 105         }
 106         pthread_mutex_unlock(mutex);
 107         return handle;
 108 }
 109