makefs/msdos/msdosfs_fat.c

74 int fc_lfcempty;		/* # of time last file cluster cache entry
80 				 * cluster mapped entry was. */
124  * Map the logical cluster number of a file into a physical disk sector
128  * findcn - file relative cluster whose filesystem relative cluster number
132  * cnp	  - address of where to place the file system relative cluster number.
136  * This function has one side effect.  If the requested file relative cluster
143 	/* findcn:		 file relative cluster to get		 */
145 	/* cnp:		 returned cluster number		 */
170 	DPRINTF(("%s(start cluster=%lu)\n", __func__, cn));
174 	 * clusters.  If the cluster number is beyond the end of the root
206 	 * All other files do I/O in cluster sized blocks
239 		 * Also stop when cluster is not in the filesystem
300 	/* update last file cluster entry in the FAT cache */
307  * Find the closest entry in the FAT cache to the cluster we are looking
332  * relative cluster frcn and beyond.
374 			 * The cluster indicated in FSInfo isn't free
453  * cluster number into the appropriate bytes in the FAT.
463  *	cluster n	   cluster n+1
485 clusterfree(struct msdosfsmount *pmp, u_long cluster, u_long *oldcnp)
490 	usemap_free(pmp, cluster);
491 	error = fatentry(FAT_GET_AND_SET, pmp, cluster, &oldcn, MSDOSFSFREE);
493 		usemap_alloc(pmp, cluster);
497 	 * If the cluster was successfully marked free, then update
499 	 * bit in the "in use" cluster bit map.
507  * Get or Set or 'Get and Set' the cluster'th entry in the FAT.
512  * cn		- which cluster is of interest
514  *		  cluster'th entry if this is a get function
515  * newcontents	- the new value to be written into the cluster'th element of
518  * This function can also be used to free a cluster by setting the FAT entry
519  * for a cluster to 0.
522  * fatentry() marks a cluster as free it does not update the inusemap in
547 	 * If they asked us to return a cluster number but didn't tell us
558 	 * Be sure the requested cluster is in the filesystem.
617  * Update a contiguous cluster chain
620  * start    - first cluster of chain
622  * fillwith - what to write into FAT entry of last cluster
687  * Check the length of a free cluster chain starting at start.
728  * start      - start of cluster chain.
731  *		last allocated cluster.
732  * retcluster - put the first allocated cluster's number here.
746 	DPRINTF(("%s(): allocated cluster chain at %lu (%lu clusters)\n",
759  * start      - preferred start of cluster chain.
762  *		last allocated cluster.
763  * retcluster - put the first allocated cluster's number here.
791 	 * Start at a (pseudo) random place to maximize cluster runs
846  *		  containing the cluster chain to be freed.
847  * startcluster - number of the 1st cluster in the chain of clusters to be
851 freeclusterchain(struct msdosfsmount *pmp, u_long cluster)
858 	while (cluster >= CLUST_FIRST && cluster <= pmp->pm_maxcluster) {
859 		byteoffset = FATOFS(pmp, cluster);
871 		usemap_free(pmp, cluster);
876 			if (cluster & 1) {
877 				cluster = readcn >> 4;
881 				cluster = readcn;
888 			cluster = getushort((char *)bp->b_data + bo);
892 			cluster = getulong((char *)bp->b_data + bo);
894 				 (MSDOSFSFREE & FAT32_MASK) | (cluster & ~FAT32_MASK));
897 		cluster &= pmp->pm_fatmask;
905  * Read in FAT blocks looking for free clusters. For every free cluster
960  * Allocate a new cluster and chain it onto the end of the file.
966  * ncp	 - where to put cluster number of the first newly allocated cluster
967  *	   If this pointer is 0, do not return the cluster number.
993 	 * If the "file's last cluster" cache entry is empty, and the file
1011 		 * Allocate a new cluster chain and cat onto the end of the
1031 		 * Give them the filesystem relative cluster number if they want
1054 		 * Update the "last cluster of the file" entry in the