treefiles.c

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#include "lfs.h"
#include <fcntl.h>
#include <inttypes.h>
#include <stdio.h>
#include <unistd.h>
#include <sys/stat.h>
#include <sys/types.h>

#include <glib.h>

#include <backend.h>
#include <config.h>
#include <cliserv.h>
#include <treefiles.h>
#include <nbd-debug.h>
#include <nbdsrv.h>
/**
 * Tree structure helper functions
 */
void construct_path(char* name,int lenmax,off_t size, off_t pos, off_t * ppos) {
        if (lenmax<10)
                err("Char buffer overflow. This is likely a bug.");

        if (size<TREEDIRSIZE*TREEPAGESIZE) {
                // we are done, add filename
                snprintf(name,lenmax,"/FILE%04" PRIX64,(pos/TREEPAGESIZE) % TREEDIRSIZE);
                *ppos = pos / (TREEPAGESIZE*TREEDIRSIZE);
        } else {
                construct_path(name+9,lenmax-9,size/TREEDIRSIZE,pos,ppos);
                char buffer[10];
                snprintf(buffer,sizeof(buffer),"/TREE%04jX",(intmax_t)(*ppos % TREEDIRSIZE));
                memcpy(name,buffer,9); // copy into string without trailing zero
                *ppos/=TREEDIRSIZE;
        }
}

void delete_treefile(char* name,off_t size,off_t pos) {
        char filename[256+strlen(name)];
        strcpy(filename,name);
        off_t ppos;
        construct_path(filename+strlen(name),256,size,pos,&ppos);

        DEBUG("Deleting treefile: %s",filename);

        if (unlink(filename)==-1)
                DEBUG("Deleting failed : %s",strerror(errno));
}

void mkdir_path(char * path) {
        char *subpath=path+1;
        while ((subpath=strchr(subpath,'/'))) {
                *subpath='\0'; // path is modified in place with terminating null char instead of slash
                if (mkdir(path,0700)==-1) {
                        if (errno!=EEXIST)
                                err("Path access error! %m");
                }
                *subpath='/';
                subpath++;
        }
}

int open_treefile(char* name,mode_t mode,off_t size,off_t pos, pthread_mutex_t *mutex) {
        char filename[256+strlen(name)];
        strcpy(filename,name);
        off_t ppos;
        construct_path(filename+strlen(name),256,size,pos,&ppos);

        DEBUG("Accessing treefile %s ( offset %llu of %llu)",filename,(unsigned long long)pos,(unsigned long long)size);

        pthread_mutex_lock(mutex);
        int handle=open(filename, mode, 0600);
        if (handle<0 && errno==ENOENT) {
                if (mode & O_RDWR) {

                        DEBUG("Creating new treepath");

                        mkdir_path(filename);
                        handle=open(filename, O_RDWR|O_CREAT, 0600);
                        if (handle<0) {
                                err("Error opening tree block file %m");
                        }
                } else {

                        DEBUG("Creating a dummy tempfile for reading");
                        gchar * tmpname;
                        tmpname = g_strdup_printf("dummy-XXXXXX");
                        handle = mkstemp(tmpname);
                        if (handle>0) {
                                unlink(tmpname); /* File will stick around whilst FD open */
                        } else {
                                err("Error opening tree block file %m");
                        }
                        g_free(tmpname);
                }
                char *n = "\0";
                myseek(handle,TREEPAGESIZE-1);
                ssize_t c = write(handle,n,1);
                if (c<1) {
                        err("Error setting tree block file size %m");
                }
        }
        pthread_mutex_unlock(mutex);
        return handle;
}