Changes in uspace/srv/fs/fat/fat_fat.c [15f3c3f:7ece4247] in mainline

File:

• uspace/srv/fs/fat/fat_fat.c (modified) (29 diffs)

uspace/srv/fs/fat/fat_fat.c

@@ -1 +1 @@
 /*
  * Copyright (c) 2008 Jakub Jermar
+ * Copyright (c) 2011 Oleg Romanenko
  * All rights reserved.
  *
@@ -29 +30 @@
 /** @addtogroup fs
  * @{
- */ 
+ */
 
 /**
@@ -50 +51 @@
 #include <mem.h>
 
-/*
- * Convenience macros for computing some frequently used values from the
- * primitive boot sector members.
- */
-#define RDS(bs)         ((sizeof(fat_dentry_t) * RDE((bs))) / BPS((bs))) + \
-                        (((sizeof(fat_dentry_t) * RDE((bs))) % BPS((bs))) != 0)
-#define SSA(bs)         (RSCNT((bs)) + FATCNT((bs)) * SF((bs)) + RDS(bs))
-
-#define CLBN2PBN(bs, cl, bn) \
-        (SSA((bs)) + ((cl) - FAT_CLST_FIRST) * SPC((bs)) + (bn) % SPC((bs)))
+#define IS_ODD(number)  (number & 0x1)
 
 /**
@@ -65 +57 @@
  * during allocation of clusters. The lock does not have to be held durring
  * deallocation of clusters.
- */  
+ */
 static FIBRIL_MUTEX_INITIALIZE(fat_alloc_lock);
 
@@ -77 +69 @@
  * @param numc          If non-NULL, output argument holding the number of
  *                      clusters seen during the walk.
- * @param max_clusters  Maximum number of clusters to visit.    
+ * @param max_clusters  Maximum number of clusters to visit.
  *
  * @return              EOK on success or a negative error code.
  */
-int 
+int
 fat_cluster_walk(fat_bs_t *bs, service_id_t service_id, fat_cluster_t firstc,
-    fat_cluster_t *lastc, uint16_t *numc, uint16_t max_clusters)
-{
-        block_t *b;
-        uint16_t clusters = 0;
-        fat_cluster_t clst = firstc;
+    fat_cluster_t *lastc, uint32_t *numc, uint32_t max_clusters)
+{
+        uint32_t clusters = 0;
+        fat_cluster_t clst = firstc, clst_last1 = FAT_CLST_LAST1(bs);
+        fat_cluster_t clst_bad = FAT_CLST_BAD(bs);
         int rc;
 
@@ -99 +91 @@
         }
 
-        while (clst < FAT_CLST_LAST1 && clusters < max_clusters) {
-                aoff64_t fsec;  /* sector offset relative to FAT1 */
-                unsigned fidx;  /* FAT1 entry index */
-
+        while (clst < clst_last1 && clusters < max_clusters) {
                 assert(clst >= FAT_CLST_FIRST);
                 if (lastc)
                         *lastc = clst;  /* remember the last cluster number */
-                fsec = (clst * sizeof(fat_cluster_t)) / BPS(bs);
-                fidx = clst % (BPS(bs) / sizeof(fat_cluster_t));
+
                 /* read FAT1 */
-                rc = block_get(&b, service_id, RSCNT(bs) + fsec,
-                    BLOCK_FLAGS_NONE);
-                if (rc != EOK)
-                        return rc;
-                clst = uint16_t_le2host(((fat_cluster_t *)b->data)[fidx]);
-                assert(clst != FAT_CLST_BAD);
-                rc = block_put(b);
-                if (rc != EOK)
-                        return rc;
+                rc = fat_get_cluster(bs, service_id, FAT1, clst, &clst);
+                if (rc != EOK)
+                        return rc;
+
+                assert(clst != clst_bad);
                 clusters++;
         }
 
-        if (lastc && clst < FAT_CLST_LAST1)
+        if (lastc && clst < clst_last1)
                 *lastc = clst;
         if (numc)
@@ -151 +135 @@
                 return ELIMIT;
 
-        if (nodep->firstc == FAT_CLST_ROOT) 
+        if (!FAT_IS_FAT32(bs) && nodep->firstc == FAT_CLST_ROOT)
                 goto fall_through;
 
@@ -178 +162 @@
         if (rc != EOK)
                 return rc;
-        
+
         /*
          * Update the "current" cluster cache.
@@ -198 +182 @@
  * @param clp           If not NULL, address where the cluster containing bn
  *                      will be stored.
- *                      stored 
+ *                      stored
  * @param bn            Block number.
  * @param flags         Flags passed to libblock.
@@ -208 +192 @@
     fat_cluster_t fcl, fat_cluster_t *clp, aoff64_t bn, int flags)
 {
-        uint16_t clusters;
-        unsigned max_clusters;
+        uint32_t clusters;
+        uint32_t max_clusters;
         fat_cluster_t c;
         int rc;
@@ -219 +203 @@
                 return ELIMIT;
 
-        if (fcl == FAT_CLST_ROOT) {
+        if (!FAT_IS_FAT32(bs) && fcl == FAT_CLST_ROOT) {
                 /* root directory special case */
                 assert(bn < RDS(bs));
@@ -253 +237 @@
  * @return              EOK on success or a negative error code.
  */
-int fat_fill_gap(fat_bs_t *bs, fat_node_t *nodep, fat_cluster_t mcl, aoff64_t pos)
+int
+fat_fill_gap(fat_bs_t *bs, fat_node_t *nodep, fat_cluster_t mcl, aoff64_t pos)
 {
         block_t *b;
@@ -275 +260 @@
                         return rc;
         }
-        
+
         if (o >= pos)
                 return EOK;
-        
+
         /* zero out the initial part of the new cluster chain */
         for (o = boundary; o < pos; o += BPS(bs)) {
@@ -304 +289 @@
  * @return              EOK or a negative error code.
  */
+static int
+fat_get_cluster_fat12(fat_bs_t *bs, service_id_t service_id, unsigned fatno,
+    fat_cluster_t clst, fat_cluster_t *value)
+{
+        block_t *b, *b1;
+        uint16_t byte1, byte2;
+        aoff64_t offset;
+        int rc;
+
+        offset = (clst + clst / 2);
+        if (offset / BPS(bs) >= SF(bs))
+                return ERANGE;
+
+        rc = block_get(&b, service_id, RSCNT(bs) + SF(bs) * fatno +
+            offset / BPS(bs), BLOCK_FLAGS_NONE);
+        if (rc != EOK)
+                return rc;
+
+        byte1 = ((uint8_t *) b->data)[offset % BPS(bs)];
+        /* This cluster access spans a sector boundary. Check only for FAT12 */
+        if ((offset % BPS(bs)) + 1 == BPS(bs)) {
+                /* Is this the last sector of FAT? */
+                if (offset / BPS(bs) < SF(bs)) {
+                        /* No, read the next sector */
+                        rc = block_get(&b1, service_id, 1 + RSCNT(bs) +
+                            SF(bs) * fatno + offset / BPS(bs),
+                            BLOCK_FLAGS_NONE);
+                        if (rc != EOK) {
+                                block_put(b);
+                                return rc;
+                        }
+                        /*
+                        * Combining value with last byte of current sector and
+                        * first byte of next sector
+                        */
+                        byte2 = ((uint8_t*) b1->data)[0];
+
+                        rc = block_put(b1);
+                        if (rc != EOK) {
+                                block_put(b);
+                                return rc;
+                        }
+                } else {
+                        /* Yes. This is the last sector of FAT */
+                        block_put(b);
+                        return ERANGE;
+                }
+        } else
+                byte2 = ((uint8_t *) b->data)[(offset % BPS(bs)) + 1];
+
+        *value = uint16_t_le2host(byte1 | (byte2 << 8));
+        if (IS_ODD(clst))
+                *value = (*value) >> 4;
+        else
+                *value = (*value) & FAT12_MASK;
+        
+        rc = block_put(b);
+
+        return rc;
+}
+
+/** Get cluster from the first FAT.
+ *
+ * @param bs            Buffer holding the boot sector for the file system.
+ * @param service_id    Service ID for the file system.
+ * @param clst          Cluster which to get.
+ * @param value         Output argument holding the value of the cluster.
+ *
+ * @return              EOK or a negative error code.
+ */
+static int
+fat_get_cluster_fat16(fat_bs_t *bs, service_id_t service_id, unsigned fatno,
+    fat_cluster_t clst, fat_cluster_t *value)
+{
+        block_t *b;
+        aoff64_t offset;
+        int rc;
+
+        offset = (clst * FAT16_CLST_SIZE);
+
+        rc = block_get(&b, service_id, RSCNT(bs) + SF(bs) * fatno +
+            offset / BPS(bs), BLOCK_FLAGS_NONE);
+        if (rc != EOK)
+                return rc;
+
+        *value = uint16_t_le2host(*(uint16_t *)(b->data + offset % BPS(bs)));
+
+        rc = block_put(b);
+
+        return rc;
+}
+
+/** Get cluster from the first FAT.
+ *
+ * @param bs            Buffer holding the boot sector for the file system.
+ * @param service_id    Service ID for the file system.
+ * @param clst          Cluster which to get.
+ * @param value         Output argument holding the value of the cluster.
+ *
+ * @return              EOK or a negative error code.
+ */
+static int
+fat_get_cluster_fat32(fat_bs_t *bs, service_id_t service_id, unsigned fatno,
+    fat_cluster_t clst, fat_cluster_t *value)
+{
+        block_t *b;
+        aoff64_t offset;
+        int rc;
+
+        offset = (clst * FAT32_CLST_SIZE);
+
+        rc = block_get(&b, service_id, RSCNT(bs) + SF(bs) * fatno +
+            offset / BPS(bs), BLOCK_FLAGS_NONE);
+        if (rc != EOK)
+                return rc;
+
+        *value = uint32_t_le2host(*(uint32_t *)(b->data + offset % BPS(bs))) &
+            FAT32_MASK;
+
+        rc = block_put(b);
+
+        return rc;
+}
+
+
+/** Get cluster from the first FAT.
+ *
+ * @param bs            Buffer holding the boot sector for the file system.
+ * @param service_id    Service ID for the file system.
+ * @param clst          Cluster which to get.
+ * @param value         Output argument holding the value of the cluster.
+ *
+ * @return              EOK or a negative error code.
+ */
 int
 fat_get_cluster(fat_bs_t *bs, service_id_t service_id, unsigned fatno,
     fat_cluster_t clst, fat_cluster_t *value)
 {
-        block_t *b;
-        fat_cluster_t *cp;
-        int rc;
-
+        int rc;
+
+        assert(fatno < FATCNT(bs));
+
+        if (FAT_IS_FAT12(bs))
+                rc = fat_get_cluster_fat12(bs, service_id, fatno, clst, value);
+        else if (FAT_IS_FAT16(bs))
+                rc = fat_get_cluster_fat16(bs, service_id, fatno, clst, value);
+        else
+                rc = fat_get_cluster_fat32(bs, service_id, fatno, clst, value);
+
+        return rc;
+}
+
+/** Set cluster in one instance of FAT.
+ *
+ * @param bs            Buffer holding the boot sector for the file system.
+ * @param service_id    Service ID for the file system.
+ * @param fatno         Number of the FAT instance where to make the change.
+ * @param clst          Cluster which is to be set.
+ * @param value         Value to set the cluster with.
+ *
+ * @return              EOK on success or a negative error code.
+ */
+static int
+fat_set_cluster_fat12(fat_bs_t *bs, service_id_t service_id, unsigned fatno,
+    fat_cluster_t clst, fat_cluster_t value)
+{
+        block_t *b, *b1 = NULL;
+        aoff64_t offset;
+        uint16_t byte1, byte2;
+        int rc;
+
+        offset = (clst + clst / 2);
+        if (offset / BPS(bs) >= SF(bs))
+                return ERANGE;
+        
         rc = block_get(&b, service_id, RSCNT(bs) + SF(bs) * fatno +
-            (clst * sizeof(fat_cluster_t)) / BPS(bs), BLOCK_FLAGS_NONE);
+            offset / BPS(bs), BLOCK_FLAGS_NONE);
         if (rc != EOK)
                 return rc;
-        cp = (fat_cluster_t *)b->data +
-            clst % (BPS(bs) / sizeof(fat_cluster_t));
-        *value = uint16_t_le2host(*cp);
+
+        byte1 = ((uint8_t*) b->data)[offset % BPS(bs)];
+        bool border = false;
+        /* This cluster access spans a sector boundary. */
+        if ((offset % BPS(bs)) + 1 == BPS(bs)) {
+                /* Is it the last sector of FAT? */
+                if (offset / BPS(bs) < SF(bs)) {
+                        /* No, read the next sector */
+                        rc = block_get(&b1, service_id, 1 + RSCNT(bs) +
+                            SF(bs) * fatno + offset / BPS(bs),
+                            BLOCK_FLAGS_NONE);
+                        if (rc != EOK) {
+                                block_put(b);
+                                return rc;
+                        }
+                        /*
+                         * Combining value with last byte of current sector and
+                         * first byte of next sector
+                         */
+                        byte2 = ((uint8_t *) b1->data)[0];
+                        border = true;
+                } else {
+                        /* Yes. This is the last sector of FAT */
+                        block_put(b);
+                        return ERANGE;
+                }
+        } else
+                byte2 = ((uint8_t*) b->data)[(offset % BPS(bs)) + 1];
+
+        if (IS_ODD(clst)) {
+                byte1 &= 0x0f;
+                byte2 = 0;
+                value = (value << 4);
+        } else {
+                byte1 = 0;
+                byte2 &= 0xf0;
+                value &= FAT12_MASK;
+        }
+
+        byte1 = byte1 | (value & 0xff);
+        byte2 = byte2 | (value >> 8);
+
+        ((uint8_t *) b->data)[(offset % BPS(bs))] = byte1;
+        if (border) {
+                ((uint8_t *) b1->data)[0] = byte2;
+
+                b1->dirty = true;
+                rc = block_put(b1);
+                if (rc != EOK) {
+                        block_put(b);
+                        return rc;
+                }
+        } else 
+                ((uint8_t *) b->data)[(offset % BPS(bs)) + 1] = byte2;
+
+        b->dirty = true;        /* need to sync block */
         rc = block_put(b);
-        
+
+        return rc;
+}
+
+/** Set cluster in one instance of FAT.
+ *
+ * @param bs            Buffer holding the boot sector for the file system.
+ * @param service_id    Service ID for the file system.
+ * @param fatno         Number of the FAT instance where to make the change.
+ * @param clst          Cluster which is to be set.
+ * @param value         Value to set the cluster with.
+ *
+ * @return              EOK on success or a negative error code.
+ */
+static int
+fat_set_cluster_fat16(fat_bs_t *bs, service_id_t service_id, unsigned fatno,
+    fat_cluster_t clst, fat_cluster_t value)
+{
+        block_t *b;
+        aoff64_t offset;
+        int rc;
+
+        offset = (clst * FAT16_CLST_SIZE);
+
+        rc = block_get(&b, service_id, RSCNT(bs) + SF(bs) * fatno +
+            offset / BPS(bs), BLOCK_FLAGS_NONE);
+        if (rc != EOK)
+                return rc;
+
+        *(uint16_t *)(b->data + offset % BPS(bs)) = host2uint16_t_le(value);
+
+        b->dirty = true;        /* need to sync block */
+        rc = block_put(b);
+
+        return rc;
+}
+
+/** Set cluster in one instance of FAT.
+ *
+ * @param bs            Buffer holding the boot sector for the file system.
+ * @param service_id    Service ID for the file system.
+ * @param fatno         Number of the FAT instance where to make the change.
+ * @param clst          Cluster which is to be set.
+ * @param value         Value to set the cluster with.
+ *
+ * @return              EOK on success or a negative error code.
+ */
+static int
+fat_set_cluster_fat32(fat_bs_t *bs, service_id_t service_id, unsigned fatno,
+    fat_cluster_t clst, fat_cluster_t value)
+{
+        block_t *b;
+        aoff64_t offset;
+        int rc;
+        fat_cluster_t temp;
+
+        offset = (clst * FAT32_CLST_SIZE);
+
+        rc = block_get(&b, service_id, RSCNT(bs) + SF(bs) * fatno +
+            offset / BPS(bs), BLOCK_FLAGS_NONE);
+        if (rc != EOK)
+                return rc;
+
+        temp = uint32_t_le2host(*(uint32_t *)(b->data + offset % BPS(bs)));
+        temp &= 0xf0000000;
+        temp |= (value & FAT32_MASK);
+        *(uint32_t *)(b->data + offset % BPS(bs)) = host2uint32_t_le(temp);
+
+        b->dirty = true;        /* need to sync block */
+        rc = block_put(b);
+
         return rc;
 }
@@ -338 +613 @@
     fat_cluster_t clst, fat_cluster_t value)
 {
-        block_t *b;
-        fat_cluster_t *cp;
         int rc;
 
         assert(fatno < FATCNT(bs));
-        rc = block_get(&b, service_id, RSCNT(bs) + SF(bs) * fatno +
-            (clst * sizeof(fat_cluster_t)) / BPS(bs), BLOCK_FLAGS_NONE);
-        if (rc != EOK)
-                return rc;
-        cp = (fat_cluster_t *)b->data +
-            clst % (BPS(bs) / sizeof(fat_cluster_t));
-        *cp = host2uint16_t_le(value);
-        b->dirty = true;                /* need to sync block */
-        rc = block_put(b);
+
+        if (FAT_IS_FAT12(bs))
+                rc = fat_set_cluster_fat12(bs, service_id, fatno, clst, value);
+        else if (FAT_IS_FAT16(bs))
+                rc = fat_set_cluster_fat16(bs, service_id, fatno, clst, value);
+        else
+                rc = fat_set_cluster_fat32(bs, service_id, fatno, clst, value);
+
         return rc;
 }
@@ -369 +641 @@
         uint8_t fatno;
         unsigned c;
-        int rc;
-
-        for (fatno = FAT1 + 1; fatno < bs->fatcnt; fatno++) {
+        fat_cluster_t clst_last1 = FAT_CLST_LAST1(bs);
+        int rc;
+
+        for (fatno = FAT1 + 1; fatno < FATCNT(bs); fatno++) {
                 for (c = 0; c < nclsts; c++) {
                         rc = fat_set_cluster(bs, service_id, fatno, lifo[c],
-                            c == 0 ? FAT_CLST_LAST1 : lifo[c - 1]);
+                            c == 0 ? clst_last1 : lifo[c - 1]);
                         if (rc != EOK)
                                 return rc;
@@ -404 +677 @@
     fat_cluster_t *mcl, fat_cluster_t *lcl)
 {
-        block_t *blk;
-        fat_cluster_t *lifo;    /* stack for storing free cluster numbers */ 
-        unsigned found = 0;     /* top of the free cluster number stack */
-        unsigned b, c, cl; 
-        int rc;
+        fat_cluster_t *lifo;    /* stack for storing free cluster numbers */
+        unsigned found = 0;     /* top of the free cluster number stack */
+        fat_cluster_t clst, value, clst_last1 = FAT_CLST_LAST1(bs);
+        int rc = EOK;
 
         lifo = (fat_cluster_t *) malloc(nclsts * sizeof(fat_cluster_t));
         if (!lifo)
                 return ENOMEM;
-        
         /*
          * Search FAT1 for unused clusters.
          */
         fibril_mutex_lock(&fat_alloc_lock);
-        for (b = 0, cl = 0; b < SF(bs); b++) {
-                rc = block_get(&blk, service_id, RSCNT(bs) + b,
-                    BLOCK_FLAGS_NONE);
-                if (rc != EOK)
-                        goto error;
-                for (c = 0; c < BPS(bs) / sizeof(fat_cluster_t); c++, cl++) {
+        for (clst = FAT_CLST_FIRST; clst < CC(bs) + 2 && found < nclsts;
+            clst++) {
+                rc = fat_get_cluster(bs, service_id, FAT1, clst, &value);
+                if (rc != EOK)
+                        break;
+
+                if (value == FAT_CLST_RES0) {
                         /*
-                         * Check if the entire cluster is physically there.
-                         * This check becomes necessary when the file system is
-                         * created with fewer total sectors than how many is
-                         * inferred from the size of the file allocation table
-                         * or when the last cluster ends beyond the end of the
-                         * device.
+                         * The cluster is free. Put it into our stack
+                         * of found clusters and mark it as non-free.
                          */
-                        if ((cl >= FAT_CLST_FIRST) &&
-                            CLBN2PBN(bs, cl, SPC(bs) - 1) >= TS(bs)) {
-                                rc = block_put(blk);
-                                if (rc != EOK)
-                                        goto error;
-                                goto out;
-                        }
-
-                        fat_cluster_t *clst = (fat_cluster_t *)blk->data + c;
-                        if (uint16_t_le2host(*clst) == FAT_CLST_RES0) {
-                                /*
-                                 * The cluster is free. Put it into our stack
-                                 * of found clusters and mark it as non-free.
-                                 */
-                                lifo[found] = cl;
-                                *clst = (found == 0) ?
-                                    host2uint16_t_le(FAT_CLST_LAST1) :
-                                    host2uint16_t_le(lifo[found - 1]);
-                                blk->dirty = true;      /* need to sync block */
-                                if (++found == nclsts) {
-                                        /* we are almost done */
-                                        rc = block_put(blk);
-                                        if (rc != EOK)
-                                                goto error;
-                                        /* update the shadow copies of FAT */
-                                        rc = fat_alloc_shadow_clusters(bs,
-                                            service_id, lifo, nclsts);
-                                        if (rc != EOK)
-                                                goto error;
-                                        *mcl = lifo[found - 1];
-                                        *lcl = lifo[0];
-                                        free(lifo);
-                                        fibril_mutex_unlock(&fat_alloc_lock);
-                                        return EOK;
-                                }
-                        }
+                        lifo[found] = clst;
+                        rc = fat_set_cluster(bs, service_id, FAT1, clst,
+                            (found == 0) ?  clst_last1 : lifo[found - 1]);
+                        if (rc != EOK)
+                                break;
+
+                        found++;
                 }
-                rc = block_put(blk);
-                if (rc != EOK) {
-error:
+        }
+
+        if (rc == EOK && found == nclsts) {
+                rc = fat_alloc_shadow_clusters(bs, service_id, lifo, nclsts);
+                if (rc == EOK) {
+                        *mcl = lifo[found - 1];
+                        *lcl = lifo[0];
+                        free(lifo);
                         fibril_mutex_unlock(&fat_alloc_lock);
-                        free(lifo);
-                        return rc;
+                        return EOK;
                 }
         }
-out:
+
+        /* If something wrong - free the clusters */
+        while (found--) {
+                (void) fat_set_cluster(bs, service_id, FAT1, lifo[found],
+                    FAT_CLST_RES0);
+        }
+
+        free(lifo);
         fibril_mutex_unlock(&fat_alloc_lock);
 
-        /*
-         * We could not find enough clusters. Now we need to free the clusters
-         * we have allocated so far.
-         */
-        while (found--) {
-                rc = fat_set_cluster(bs, service_id, FAT1, lifo[found],
-                    FAT_CLST_RES0);
-                if (rc != EOK) {
-                        free(lifo);
-                        return rc;
-                }
-        }
-        
-        free(lifo);
         return ENOSPC;
 }
@@ -509 +745 @@
 {
         unsigned fatno;
-        fat_cluster_t nextc;
+        fat_cluster_t nextc, clst_bad = FAT_CLST_BAD(bs);
         int rc;
 
         /* Mark all clusters in the chain as free in all copies of FAT. */
-        while (firstc < FAT_CLST_LAST1) {
-                assert(firstc >= FAT_CLST_FIRST && firstc < FAT_CLST_BAD);
+        while (firstc < FAT_CLST_LAST1(bs)) {
+                assert(firstc >= FAT_CLST_FIRST && firstc < clst_bad);
+
                 rc = fat_get_cluster(bs, service_id, FAT1, firstc, &nextc);
                 if (rc != EOK)
                         return rc;
-                for (fatno = FAT1; fatno < bs->fatcnt; fatno++) {
+
+                for (fatno = FAT1; fatno < FATCNT(bs); fatno++) {
                         rc = fat_set_cluster(bs, service_id, fatno, firstc,
                             FAT_CLST_RES0);
@@ -524 +762 @@
                                 return rc;
                 }
-
                 firstc = nextc;
         }
@@ -540 +777 @@
  * @return              EOK on success or a negative error code.
  */
-int
-fat_append_clusters(fat_bs_t *bs, fat_node_t *nodep, fat_cluster_t mcl,
+int fat_append_clusters(fat_bs_t *bs, fat_node_t *nodep, fat_cluster_t mcl,
     fat_cluster_t lcl)
 {
@@ -559 +795 @@
                 } else {
                         rc = fat_cluster_walk(bs, service_id, nodep->firstc,
-                            &lastc, NULL, (uint16_t) -1);
+                            &lastc, NULL, (uint32_t) -1);
                         if (rc != EOK)
                                 return rc;
                 }
 
-                for (fatno = FAT1; fatno < bs->fatcnt; fatno++) {
-                        rc = fat_set_cluster(bs, nodep->idx->service_id, fatno,
-                            lastc, mcl);
+                for (fatno = FAT1; fatno < FATCNT(bs); fatno++) {
+                        rc = fat_set_cluster(bs, nodep->idx->service_id,
+                            fatno, lastc, mcl);
                         if (rc != EOK)
                                 return rc;
@@ -590 +826 @@
 int fat_chop_clusters(fat_bs_t *bs, fat_node_t *nodep, fat_cluster_t lcl)
 {
+        fat_cluster_t clst_last1 = FAT_CLST_LAST1(bs);
         int rc;
         service_id_t service_id = nodep->idx->service_id;
@@ -616 +853 @@
 
                 /* Terminate the cluster chain in all copies of FAT. */
-                for (fatno = FAT1; fatno < bs->fatcnt; fatno++) {
+                for (fatno = FAT1; fatno < FATCNT(bs); fatno++) {
                         rc = fat_set_cluster(bs, service_id, fatno, lcl,
-                            FAT_CLST_LAST1);
+                            clst_last1);
                         if (rc != EOK)
                                 return rc;
@@ -673 +910 @@
 
         /* Check number of FATs. */
-        if (bs->fatcnt == 0)
+        if (FATCNT(bs) == 0)
                 return ENOTSUP;
 
         /* Check total number of sectors. */
-
-        if (bs->totsec16 == 0 && bs->totsec32 == 0)
+        if (TS(bs) == 0)
                 return ENOTSUP;
 
         if (bs->totsec16 != 0 && bs->totsec32 != 0 &&
-            bs->totsec16 != bs->totsec32) 
+            bs->totsec16 != bs->totsec32)
                 return ENOTSUP;
 
@@ -690 +926 @@
 
         /* Check number of sectors per FAT. */
-        if (bs->sec_per_fat == 0)
+        if (SF(bs) == 0)
                 return ENOTSUP;
 
@@ -700 +936 @@
          * sanitized to support file systems with this property.
          */
-        if ((uint16_t_le2host(bs->root_ent_max) * sizeof(fat_dentry_t)) %
-            uint16_t_le2host(bs->bps) != 0)
+        if (!FAT_IS_FAT32(bs) &&
+            (RDE(bs) * sizeof(fat_dentry_t)) % BPS(bs) != 0)
                 return ENOTSUP;
 
         /* Check signature of each FAT. */
-
-        for (fat_no = 0; fat_no < bs->fatcnt; fat_no++) {
+        for (fat_no = 0; fat_no < FATCNT(bs); fat_no++) {
                 rc = fat_get_cluster(bs, service_id, fat_no, 0, &e0);
                 if (rc != EOK)
@@ -715 +950 @@
                         return EIO;
 
-                /* Check that first byte of FAT contains the media descriptor. */
+                /*
+                 * Check that first byte of FAT contains the media descriptor.
+                 */
                 if ((e0 & 0xff) != bs->mdesc)
                         return ENOTSUP;
@@ -723 +960 @@
                  * set to one.
                  */
-                if ((e0 >> 8) != 0xff || e1 != 0xffff)
+                if (!FAT_IS_FAT12(bs) && 
+                    ((e0 >> 8) != (FAT_MASK(bs) >> 8) || e1 != FAT_MASK(bs)))
                         return ENOTSUP;
         }
@@ -732 +970 @@
 /**
  * @}
- */ 
+ */