WebSVN – HelenOS – Diff – //branches/tracing/uspace/srv/fs/fat/fat_fat.c

  * during allocation of clusters. The lock does not have to be held durring
  * deallocation of clusters.
  */
 static futex_t fat_alloc_lock = FUTEX_INITIALIZER;
-/** Read block from file located on a FAT file system.
+/** Walk the cluster chain.
+ *
- * @param bs        Buffer holding the boot sector of the file system.
+ * @param bs        Buffer holding the boot sector for the file.
- * @param dev_handle    Device handle of the file system.
+ * @param dev_handle    Device handle of the device with the file.
- * @param firstc    First cluster used by the file. Can be zero if the file
+ * @param firstc    First cluster to start the walk with.
- *          is empty.
+ * @param lastc     If non-NULL, output argument hodling the last cluster number visited.
- * @param offset    Offset in blocks.
+ * @param max_clusters  Maximum number of clusters to visit.
+ *
- * @return      Block structure holding the requested block.
+ * @return      Number of clusters seen during the walk.
  */
-block_t *
+uint16_t
-_fat_block_get(fat_bs_t *bs, dev_handle_t dev_handle, fat_cluster_t firstc,
+fat_cluster_walk(fat_bs_t *bs, dev_handle_t dev_handle, fat_cluster_t firstc,
-    off_t offset)
+    fat_cluster_t *lastc, uint16_t max_clusters)
+{
     block_t *b;
     unsigned bps;
-    unsigned spc;
     unsigned rscnt;     /* block address of the first FAT */
-    unsigned fatcnt;
-    unsigned rde;
-    unsigned rds;       /* root directory size */
-    unsigned sf;
-    unsigned ssa;       /* size of the system area */
-    unsigned clusters;
+    uint16_t clusters = 0;
     fat_cluster_t clst = firstc;
-    unsigned i;
     bps = uint16_t_le2host(bs->bps);
-    spc = bs->spc;
     rscnt = uint16_t_le2host(bs->rscnt);
-    fatcnt = bs->fatcnt;
-    rde = uint16_t_le2host(bs->root_ent_max);
-    sf = uint16_t_le2host(bs->sec_per_fat);
-    rds = (sizeof(fat_dentry_t) * rde) / bps;
-    rds += ((sizeof(fat_dentry_t) * rde) % bps != 0);
-    ssa = rscnt + fatcnt * sf + rds;
-    if (firstc == FAT_CLST_ROOT) {
+    if (firstc == FAT_CLST_RES0) {
-        /* root directory special case */
+        /* No space allocated to the file. */
-        assert(offset < rds);
+        if (lastc)
-        b = block_get(dev_handle, rscnt + fatcnt * sf + offset, bps);
+            *lastc = firstc;
-        return b;
+        return 0;
+    }
-    clusters = offset / spc;
-    for (i = 0; i < clusters; i++) {
+    while (clst < FAT_CLST_LAST1 && clusters < max_clusters) {
-        unsigned fsec;  /* sector offset relative to FAT1 */
+        bn_t fsec;  /* sector offset relative to FAT1 */
         unsigned fidx;  /* FAT1 entry index */
-        assert(clst >= FAT_CLST_FIRST && clst < FAT_CLST_BAD);
+        assert(clst >= FAT_CLST_FIRST);
+        if (lastc)
+            *lastc = clst;  /* remember the last cluster number */
         fsec = (clst * sizeof(fat_cluster_t)) / bps;
         fidx = clst % (bps / sizeof(fat_cluster_t));
         /* read FAT1 */
-        b = block_get(dev_handle, rscnt + fsec, bps);
+        b = block_get(dev_handle, rscnt + fsec, BLOCK_FLAGS_NONE);
         clst = uint16_t_le2host(((fat_cluster_t *)b->data)[fidx]);
         assert(clst != FAT_CLST_BAD);
-        assert(clst < FAT_CLST_LAST1);
         block_put(b);
+        clusters++;
+    }
-    b = block_get(dev_handle, ssa + (clst - FAT_CLST_FIRST) * spc +
+    if (lastc && clst < FAT_CLST_LAST1)
-        offset % spc, bps);
+        *lastc = clst;
-    return b;
+    return clusters;
+}
-/** Return number of blocks allocated to a file.
+/** Read block from file located on a FAT file system.
+ *
- * @param bs        Buffer holding the boot sector for the file.
+ * @param bs        Buffer holding the boot sector of the file system.
- * @param dev_handle    Device handle of the device with the file.
+ * @param dev_handle    Device handle of the file system.
- * @param firstc    First cluster of the file.
+ * @param firstc    First cluster used by the file. Can be zero if the file
+ *          is empty.
- * @param lastc     If non-NULL, output argument holding the
+ * @param bn        Block number.
- *          last cluster.
+ * @param flags     Flags passed to libblock.
+ *
- * @return      Number of blocks allocated to the file.
+ * @return      Block structure holding the requested block.
  */
-uint16_t
+block_t *
-_fat_blcks_get(fat_bs_t *bs, dev_handle_t dev_handle, fat_cluster_t firstc,
+_fat_block_get(fat_bs_t *bs, dev_handle_t dev_handle, fat_cluster_t firstc,
-    fat_cluster_t *lastc)
+    bn_t bn, int flags)
+{
     block_t *b;
     unsigned bps;
-    unsigned spc;
     unsigned rscnt;     /* block address of the first FAT */
+    unsigned rde;
+    unsigned rds;       /* root directory size */
+    unsigned sf;
+    unsigned ssa;       /* size of the system area */
-    unsigned clusters = 0;
+    unsigned clusters, max_clusters;
-    fat_cluster_t clst = firstc;
+    fat_cluster_t lastc;
     bps = uint16_t_le2host(bs->bps);
-    spc = bs->spc;
     rscnt = uint16_t_le2host(bs->rscnt);
+    rde = uint16_t_le2host(bs->root_ent_max);
+    sf = uint16_t_le2host(bs->sec_per_fat);
+    rds = (sizeof(fat_dentry_t) * rde) / bps;
+    rds += ((sizeof(fat_dentry_t) * rde) % bps != 0);
+    ssa = rscnt + bs->fatcnt * sf + rds;
-    if (firstc == FAT_CLST_RES0) {
+    if (firstc == FAT_CLST_ROOT) {
-        /* No space allocated to the file. */
+        /* root directory special case */
-        if (lastc)
+        assert(bn < rds);
-            *lastc = firstc;
+        b = block_get(dev_handle, rscnt + bs->fatcnt * sf + bn, flags);
-        return 0;
+        return b;
+    }
-    while (clst < FAT_CLST_LAST1) {
+    max_clusters = bn / bs->spc;
-        unsigned fsec;  /* sector offset relative to FAT1 */
+    clusters = fat_cluster_walk(bs, dev_handle, firstc, &lastc,
+        max_clusters);
-        unsigned fidx;  /* FAT1 entry index */
+    assert(clusters == max_clusters);
-        assert(clst >= FAT_CLST_FIRST);
-        if (lastc)
-            *lastc = clst;      /* remember the last cluster */
-        fsec = (clst * sizeof(fat_cluster_t)) / bps;
-        fidx = clst % (bps / sizeof(fat_cluster_t));
-        /* read FAT1 */
-        b = block_get(dev_handle, rscnt + fsec, bps);
+    b = block_get(dev_handle, ssa + (lastc - FAT_CLST_FIRST) * bs->spc +
-        clst = uint16_t_le2host(((fat_cluster_t *)b->data)[fidx]);
-        assert(clst != FAT_CLST_BAD);
+        bn % bs->spc, flags);
-        block_put(b);
-        clusters++;
-    }
-    if (lastc)
-        *lastc = clst;
-    return clusters * spc;
+    return b;
+}
 /** Fill the gap between EOF and a new file position.
+ *
  * @param bs        Buffer holding the boot sector for nodep.
     boundary = ROUND_UP(nodep->size, bps * spc);
     /* zero out already allocated space */
     for (o = nodep->size - 1; o < pos && o < boundary;
         o = ALIGN_DOWN(o + bps, bps)) {
+            int flags = (o % bps == 0) ?
+            BLOCK_FLAGS_NOREAD : BLOCK_FLAGS_NONE;
-        b = fat_block_get(bs, nodep, o / bps);
+        b = fat_block_get(bs, nodep, o / bps, flags);
         memset(b->data + o % bps, 0, bps - o % bps);
         b->dirty = true;        /* need to sync node */
         block_put(b);
+    }
         return;
     /* zero out the initial part of the new cluster chain */
     for (o = boundary; o < pos; o += bps) {
         b = _fat_block_get(bs, nodep->idx->dev_handle, mcl,
-            (o - boundary) / bps);
+            (o - boundary) / bps, BLOCK_FLAGS_NOREAD);
         memset(b->data, 0, min(bps, pos - o));
         b->dirty = true;        /* need to sync node */
         block_put(b);
+    }
+}
+/** Get cluster from the first FAT.
+ *
+ * @param bs        Buffer holding the boot sector for the file system.
+ * @param dev_handle    Device handle for the file system.
+ * @param clst      Cluster which to get.
+ *
+ * @return      Value found in the cluster.
+ */
+fat_cluster_t
+fat_get_cluster(fat_bs_t *bs, dev_handle_t dev_handle, fat_cluster_t clst)
+{
+    block_t *b;
+    uint16_t bps;
+    uint16_t rscnt;
+    fat_cluster_t *cp, value;
+    bps = uint16_t_le2host(bs->bps);
+    rscnt = uint16_t_le2host(bs->rscnt);
+    b = block_get(dev_handle, rscnt + (clst * sizeof(fat_cluster_t)) / bps,
+        BLOCK_FLAGS_NONE);
+    cp = (fat_cluster_t *)b->data + clst % (bps / sizeof(fat_cluster_t));
+    value = uint16_t_le2host(*cp);
+    block_put(b);
+    return value;
+}
-/** Mark cluster in one instance of FAT.
+/** Set cluster in one instance of FAT.
+ *
  * @param bs        Buffer holding the boot sector for the file system.
  * @param dev_handle    Device handle for the file system.
  * @param fatno     Number of the FAT instance where to make the change.
- * @param clst      Cluster which is to be marked.
+ * @param clst      Cluster which is to be set.
- * @param value     Value mark the cluster with.
+ * @param value     Value to set the cluster with.
  */
 void
-fat_mark_cluster(fat_bs_t *bs, dev_handle_t dev_handle, unsigned fatno,
+fat_set_cluster(fat_bs_t *bs, dev_handle_t dev_handle, unsigned fatno,
     fat_cluster_t clst, fat_cluster_t value)
+{
     block_t *b;
     uint16_t bps;
     uint16_t rscnt;
     rscnt = uint16_t_le2host(bs->rscnt);
     sf = uint16_t_le2host(bs->sec_per_fat);
     assert(fatno < bs->fatcnt);
     b = block_get(dev_handle, rscnt + sf * fatno +
-        (clst * sizeof(fat_cluster_t)) / bps, bps);
+        (clst * sizeof(fat_cluster_t)) / bps, BLOCK_FLAGS_NONE);
     cp = (fat_cluster_t *)b->data + clst % (bps / sizeof(fat_cluster_t));
     *cp = host2uint16_t_le(value);
     b->dirty = true;        /* need to sync block */
     block_put(b);
+}
     uint8_t fatno;
     unsigned c;
     for (fatno = FAT1 + 1; fatno < bs->fatcnt; fatno++) {
         for (c = 0; c < nclsts; c++) {
-            fat_mark_cluster(bs, dev_handle, fatno, lifo[c],
+            fat_set_cluster(bs, dev_handle, fatno, lifo[c],
                 c == 0 ? FAT_CLST_LAST1 : lifo[c - 1]);
+        }
+    }
+}
     /*
      * Search FAT1 for unused clusters.
      */
     futex_down(&fat_alloc_lock);
     for (b = 0, cl = 0; b < sf; blk++) {
-        blk = block_get(dev_handle, rscnt + b, bps);
+        blk = block_get(dev_handle, rscnt + b, BLOCK_FLAGS_NOREAD);
         for (c = 0; c < bps / sizeof(fat_cluster_t); c++, cl++) {
             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
     /*
      * We could not find enough clusters. Now we need to free the clusters
      * we have allocated so far.
      */
     while (found--) {
-        fat_mark_cluster(bs, dev_handle, FAT1, lifo[found],
+        fat_set_cluster(bs, dev_handle, FAT1, lifo[found],
             FAT_CLST_RES0);
+    }
     free(lifo);
     return ENOSPC;
+}
+/** Free clusters forming a cluster chain in all copies of FAT.
+ *
+ * @param bs        Buffer hodling the boot sector of the file system.
+ * @param dev_handle    Device handle of the file system.
+ * @param firstc    First cluster in the chain which is to be freed.
+ */
+void
+fat_free_clusters(fat_bs_t *bs, dev_handle_t dev_handle, fat_cluster_t firstc)
+{
+    unsigned fatno;
+    fat_cluster_t nextc;
+    /* Mark all clusters in the chain as free in all copies of FAT. */
+    while (firstc < FAT_CLST_LAST1) {
+        nextc = fat_get_cluster(bs, dev_handle, firstc);
+        assert(nextc >= FAT_CLST_FIRST && nextc < FAT_CLST_BAD);
+        for (fatno = FAT1; fatno < bs->fatcnt; fatno++)
+            fat_set_cluster(bs, dev_handle, fatno, firstc,
+                FAT_CLST_RES0);
+        firstc = nextc;
+    }
+}
 /** Append a cluster chain to the last file cluster in all FATs.
+ *
- * @param bs        Buffer holding boot sector of the file system.
+ * @param bs        Buffer holding the boot sector of the file system.
  * @param nodep     Node representing the file.
  * @param mcl       First cluster of the cluster chain to append.
  */
 void fat_append_clusters(fat_bs_t *bs, fat_node_t *nodep, fat_cluster_t mcl)
+{
     dev_handle_t dev_handle = nodep->idx->dev_handle;
     fat_cluster_t lcl;
     uint8_t fatno;
-    if (_fat_blcks_get(bs, dev_handle, nodep->firstc, &lcl) == 0) {
+    if (fat_cluster_walk(bs, dev_handle, nodep->firstc, &lcl,
+        (uint16_t) -1) == 0) {
+        /* No clusters allocated to the node yet. */
         nodep->firstc = host2uint16_t_le(mcl);
         nodep->dirty = true;        /* need to sync node */
         return;
+    }
     for (fatno = FAT1; fatno < bs->fatcnt; fatno++)
-        fat_mark_cluster(bs, nodep->idx->dev_handle, fatno, lcl, mcl);
+        fat_set_cluster(bs, nodep->idx->dev_handle, fatno, lcl, mcl);
+}
+/** Chop off node clusters in all copies of FAT.
+ *
+ * @param bs        Buffer holding the boot sector of the file system.
+ * @param nodep     FAT node where the chopping will take place.
+ * @param lastc     Last cluster which will remain in the node. If this
+ *          argument is FAT_CLST_RES0, then all clusters will
+ *          be chopped off.
+ */
+void fat_chop_clusters(fat_bs_t *bs, fat_node_t *nodep, fat_cluster_t lastc)
+{
+    dev_handle_t dev_handle = nodep->idx->dev_handle;
+    if (lastc == FAT_CLST_RES0) {
+        /* The node will have zero size and no clusters allocated. */
+        fat_free_clusters(bs, dev_handle, nodep->firstc);
+        nodep->firstc = FAT_CLST_RES0;
+        nodep->dirty = true;        /* need to sync node */
+    } else {
+        fat_cluster_t nextc;
+        unsigned fatno;
+        nextc = fat_get_cluster(bs, dev_handle, lastc);
+        /* Terminate the cluster chain in all copies of FAT. */
+        for (fatno = FAT1; fatno < bs->fatcnt; fatno++)
+            fat_set_cluster(bs, dev_handle, fatno, lastc, FAT_CLST_LAST1);
+        /* Free all following clusters. */
+        fat_free_clusters(bs, dev_handle, nextc);
+    }
+}
 /**
  * @}
  */

Subversion Repositories HelenOS

(root)//branches/tracing/uspace/srv/fs/fat/fat_fat.c – Rev 3536 → 3597