sys/msdosfs/msdosfs_fat.c

77 int fc_lfcempty;		/* # of time last file cluster cache entry
83 				 * cluster mapped entry was. */
115  * Map the logical cluster number of a file into a physical disk sector
119  * findcn - file relative cluster whose filesystem relative cluster number
123  * cnp	  - address of where to place the file system relative cluster number.
129  * This function has one side effect.  If the requested file relative cluster
163 	 * clusters.  If the cluster number is beyond the end of the root
189 	 * All other files do I/O in cluster sized blocks
242 		 * Force the special cluster numbers
243 		 * to be the same for all cluster sizes
267 	/* update last file cluster entry in the fat cache */
273  * Find the closest entry in the fat cache to the cluster we are looking
298  * relative cluster frcn and beyond.
394  * cluster number into the appropriate bytes in the FAT.
404  *	cluster n	   cluster n+1
428 clusterfree(struct msdosfsmount *pmp, uint32_t cluster, uint32_t *oldcnp)
433 	usemap_free(pmp, cluster);
434 	error = fatentry(FAT_GET_AND_SET, pmp, cluster, &oldcn, MSDOSFSFREE);
436 		usemap_alloc(pmp, cluster);
440 	 * If the cluster was successfully marked free, then update
442 	 * bit in the "in use" cluster bit map.
450  * Get or Set or 'Get and Set' the cluster'th entry in the fat.
455  * cn		- which cluster is of interest
457  *		  cluster'th entry if this is a get function
458  * newcontents	- the new value to be written into the cluster'th element of
461  * This function can also be used to free a cluster by setting the fat entry
462  * for a cluster to 0.
465  * fatentry() marks a cluster as free it does not update the inusemap in
492 	 * If they asked us to return a cluster number but didn't tell us
502 	 * Be sure the requested cluster is in the filesystem.
564  * Update a contiguous cluster chain
567  * start    - first cluster of chain
569  * fillwith - what to write into fat entry of last cluster
636  * Check the length of a free cluster chain starting at start.
685  * start      - start of cluster chain.
688  *		last allocated cluster.
689  * retcluster - put the first allocated cluster's number here.
704 	printf("clusteralloc(): allocated cluster chain at %d (%d clusters)\n",
718  * start      - preferred start of cluster chain.
721  *		last allocated cluster.
722  * retcluster - put the first allocated cluster's number here.
753 	 * Start at a (pseudo) random place to maximize cluster runs
808  *		  containing the cluster chain to be freed.
809  * startcluster - number of the 1st cluster in the chain of clusters to be
813 freeclusterchain(struct msdosfsmount *pmp, uint32_t cluster)
820 	while (cluster >= CLUST_FIRST && cluster <= pmp->pm_maxcluster) {
821 		byteoffset = FATOFS(pmp, cluster);
833 		usemap_free(pmp, cluster);
837 			if (cluster & 1) {
838 				cluster = readcn >> 4;
842 				cluster = readcn;
849 			cluster = getushort(&bp->b_data[bo]);
853 			cluster = getulong(&bp->b_data[bo]);
855 				 (MSDOSFSFREE & FAT32_MASK) | (cluster & ~FAT32_MASK));
858 		cluster &= pmp->pm_fatmask;
859 		if ((cluster | ~pmp->pm_fatmask) >= CLUST_RSRVD)
860 			cluster |= pmp->pm_fatmask;
868  * Read in fat blocks looking for free clusters. For every free cluster
922  * Allocate a new cluster and chain it onto the end of the file.
928  * ncp	 - where to put cluster number of the first newly allocated cluster
929  *	   If this pointer is 0, do not return the cluster number.
956 	 * If the "file's last cluster" cache entry is empty, and the file
970 	 * Preserve value for the last cluster before extending the file
978 		 * Allocate a new cluster chain and cat onto the end of the
997 		 * Give them the filesystem relative cluster number if they want
1020 		 * Update the "last cluster of the file" entry in the denode's fat