treefiles.c

   1 #include <fcntl.h>
   2 #include <limits.h> // for PATH_MAX
   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 "config.h"
  10 #include "cliserv.h"
  11 #include "treefiles.h"
  12 #include "nbd-debug.h"
  13
  14 /**
  15  * Tree structure helper functions
  16  */
  17 void construct_path(char* name, int lenmax, off_t size, off_t pos, off_t* ppos) {
  18         if (lenmax<10)
  19                 err("Char buffer overflow. This is likely a bug.");
  20
  21         if (size<TREEDIRSIZE*TREEPAGESIZE) {
  22                 // we are done, add filename
  23                 snprintf(name,lenmax,"/FILE%04" PRIX64,(pos/TREEPAGESIZE) % TREEDIRSIZE);
  24                 *ppos = pos / (TREEPAGESIZE*TREEDIRSIZE);
  25         } else {
  26                 construct_path(name+9,lenmax-9,size/TREEDIRSIZE,pos,ppos);
  27                 char buffer[10];
  28                 snprintf(buffer,sizeof(buffer),"/TREE%04jX",(intmax_t)(*ppos % TREEDIRSIZE));
  29                 memcpy(name,buffer,9); // copy into string without trailing zero
  30                 *ppos/=TREEDIRSIZE;
  31         }
  32 }
  33
  34 void delete_treefile(char* name, off_t size, off_t pos) {
  35         char filename[PATH_MAX];
  36         off_t ppos;
  37
  38         strncpy(filename,name,PATH_MAX-1);
  39         filename[PATH_MAX-1] = '\0';
  40         construct_path(filename+strlen(name),PATH_MAX-strlen(name)-1,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, pthread_mutex_t* mutex) {
  62         char filename[PATH_MAX];
  63         off_t ppos;
  64
  65         strncpy(filename,name,PATH_MAX-1);
  66         filename[PATH_MAX - 1] = '\0';
  67         construct_path(filename+strlen(name),PATH_MAX-strlen(name)-1,size,pos,&ppos);
  68
  69         DEBUG("Accessing treefile %s (offset %llu of %llu)",filename,(unsigned long long)pos,(unsigned long long)size);
  70
  71         pthread_mutex_lock(mutex);
  72         int handle=open(filename, mode, 0600);
  73         if (handle<0 && errno==ENOENT) {
  74                 if (mode & O_RDWR) {
  75
  76                         DEBUG("Creating new treepath");
  77
  78                         mkdir_path(filename);
  79                         handle=open(filename, O_RDWR|O_CREAT, 0600);
  80                         if (handle<0) {
  81                                 err("Error opening tree block file %m");
  82                         }
  83                 } else {
  84
  85                         DEBUG("Creating a dummy tempfile for reading");
  86                         char tmpname[] = "dummy-XXXXXX";
  87                         mode_t oldmode = umask(077);
  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                 }
  96                 char* n = "\0";
  97                 if(lseek(handle,TREEPAGESIZE-1, SEEK_SET) < 0) {
  98                         err("Could not create tree file!\n");
  99                 }
 100                 ssize_t c = write(handle,n,1);
 101                 if (c<1) {
 102                         err("Error setting tree block file size %m");
 103                 }
 104         }
 105         pthread_mutex_unlock(mutex);
 106         return handle;
 107 }
 108