patch-1.3.60 linux/fs/fat/cache.c

• Lines: 298
• Date: Wed Feb 7 09:39:27 1996
• Orig file: v1.3.59/linux/fs/fat/cache.c
• Orig date: Thu Jan 1 02:00:00 1970

diff -u --recursive --new-file v1.3.59/linux/fs/fat/cache.c linux/fs/fat/cache.c
@@ -0,0 +1,297 @@
+/*
+ *  linux/fs/msdos/cache.c
+ *
+ *  Written 1992,1993 by Werner Almesberger
+ */
+
+#include <linux/msdos_fs.h>
+#include <linux/kernel.h>
+#include <linux/errno.h>
+#include <linux/string.h>
+#include <linux/stat.h>
+
+#include "msbuffer.h"
+
+static struct fat_cache *fat_cache,cache[FAT_CACHE];
+
+/* Returns the this'th FAT entry, -1 if it is an end-of-file entry. If
+   new_value is != -1, that FAT entry is replaced by it. */
+
+int fat_access(struct super_block *sb,int nr,int new_value)
+{
+	struct buffer_head *bh,*bh2,*c_bh,*c_bh2;
+	unsigned char *p_first,*p_last;
+	int first,last,next,copy;
+
+	if ((unsigned) (nr-2) >= MSDOS_SB(sb)->clusters) return 0;
+	if (MSDOS_SB(sb)->fat_bits == 16) first = last = nr*2;
+	else {
+		first = nr*3/2;
+		last = first+1;
+	}
+	if (!(bh = bread(sb->s_dev,MSDOS_SB(sb)->fat_start+(first >>
+	    SECTOR_BITS),SECTOR_SIZE))) {
+		printk("bread in fat_access failed\n");
+		return 0;
+	}
+	if ((first >> SECTOR_BITS) == (last >> SECTOR_BITS))
+		bh2 = bh;
+	else {
+		if (!(bh2 = bread(sb->s_dev,MSDOS_SB(sb)->fat_start+(last
+		    >> SECTOR_BITS),SECTOR_SIZE))) {
+			brelse(bh);
+			printk("bread in fat_access failed\n");
+			return 0;
+		}
+	}
+	if (MSDOS_SB(sb)->fat_bits == 16) {
+		p_first = p_last = NULL; /* GCC needs that stuff */
+		next = CF_LE_W(((unsigned short *) bh->b_data)[(first &
+		    (SECTOR_SIZE-1)) >> 1]);
+		if (next >= 0xfff7) next = -1;
+	}
+	else {
+		p_first = &((unsigned char *) bh->b_data)[first & (SECTOR_SIZE-1)];
+		p_last = &((unsigned char *) bh2->b_data)[(first+1) &
+		    (SECTOR_SIZE-1)];
+		if (nr & 1) next = ((*p_first >> 4) | (*p_last << 4)) & 0xfff;
+		else next = (*p_first+(*p_last << 8)) & 0xfff;
+		if (next >= 0xff7) next = -1;
+	}
+	if (new_value != -1) {
+		if (MSDOS_SB(sb)->fat_bits == 16)
+			((unsigned short *) bh->b_data)[(first & (SECTOR_SIZE-1)) >>
+			    1] = CT_LE_W(new_value);
+		else {
+			if (nr & 1) {
+				*p_first = (*p_first & 0xf) | (new_value << 4);
+				*p_last = new_value >> 4;
+			}
+			else {
+				*p_first = new_value & 0xff;
+				*p_last = (*p_last & 0xf0) | (new_value >> 8);
+			}
+			mark_buffer_dirty(bh2, 1);
+		}
+		mark_buffer_dirty(bh, 1);
+		for (copy = 1; copy < MSDOS_SB(sb)->fats; copy++) {
+			if (!(c_bh = bread(sb->s_dev,MSDOS_SB(sb)->
+			    fat_start+(first >> SECTOR_BITS)+MSDOS_SB(sb)->
+			    fat_length*copy,SECTOR_SIZE))) break;
+			memcpy(c_bh->b_data,bh->b_data,SECTOR_SIZE);
+			mark_buffer_dirty(c_bh, 1);
+			if (bh != bh2) {
+				if (!(c_bh2 = bread(sb->s_dev,
+				    MSDOS_SB(sb)->fat_start+(first >>
+				    SECTOR_BITS)+MSDOS_SB(sb)->fat_length*copy
+				    +1,SECTOR_SIZE))) {
+					brelse(c_bh);
+					break;
+				}
+				memcpy(c_bh2->b_data,bh2->b_data,SECTOR_SIZE);
+				brelse(c_bh2);
+			}
+			brelse(c_bh);
+		}
+	}
+	brelse(bh);
+	if (bh != bh2) brelse(bh2);
+	return next;
+}
+
+
+void cache_init(void)
+{
+	static int initialized = 0;
+	int count;
+
+	if (initialized) return;
+	fat_cache = &cache[0];
+	for (count = 0; count < FAT_CACHE; count++) {
+		cache[count].device = 0;
+		cache[count].next = count == FAT_CACHE-1 ? NULL :
+		    &cache[count+1];
+	}
+	initialized = 1;
+}
+
+
+void cache_lookup(struct inode *inode,int cluster,int *f_clu,int *d_clu)
+{
+	struct fat_cache *walk;
+
+#ifdef DEBUG
+printk("cache lookup: <%s,%d> %d (%d,%d) -> ", kdevname(inode->i_dev),
+       inode->i_ino, cluster, *f_clu, *d_clu);
+#endif
+	for (walk = fat_cache; walk; walk = walk->next)
+		if (inode->i_dev == walk->device
+		    && walk->ino == inode->i_ino
+		    && walk->file_cluster <= cluster
+		    && walk->file_cluster > *f_clu) {
+			*d_clu = walk->disk_cluster;
+#ifdef DEBUG
+printk("cache hit: %d (%d)\n",walk->file_cluster,*d_clu);
+#endif
+			if ((*f_clu = walk->file_cluster) == cluster) return;
+		}
+#ifdef DEBUG
+printk("cache miss\n");
+#endif
+}
+
+
+#ifdef DEBUG
+static void list_cache(void)
+{
+	struct fat_cache *walk;
+
+	for (walk = fat_cache; walk; walk = walk->next) {
+		if (walk->device)
+			printk("<%s,%d>(%d,%d) ", kdevname(walk->device),
+			       walk->ino, walk->file_cluster, walk->disk_cluster);
+		else printk("-- ");
+	}
+	printk("\n");
+}
+#endif
+
+
+void cache_add(struct inode *inode,int f_clu,int d_clu)
+{
+	struct fat_cache *walk,*last;
+
+#ifdef DEBUG
+printk("cache add: <%s,%d> %d (%d)\n", kdevname(inode->i_dev),
+       inode->i_ino, f_clu, d_clu);
+#endif
+	last = NULL;
+	for (walk = fat_cache; walk->next; walk = (last = walk)->next)
+		if (inode->i_dev == walk->device
+		    && walk->ino == inode->i_ino
+		    && walk->file_cluster == f_clu) {
+			if (walk->disk_cluster != d_clu) {
+				printk("FAT cache corruption");
+				fat_cache_inval_inode(inode);
+				return;
+			}
+			/* update LRU */
+			if (last == NULL) return;
+			last->next = walk->next;
+			walk->next = fat_cache;
+			fat_cache = walk;
+#ifdef DEBUG
+list_cache();
+#endif
+			return;
+		}
+	walk->device = inode->i_dev;
+	walk->ino = inode->i_ino;
+	walk->file_cluster = f_clu;
+	walk->disk_cluster = d_clu;
+	last->next = NULL;
+	walk->next = fat_cache;
+	fat_cache = walk;
+#ifdef DEBUG
+list_cache();
+#endif
+}
+
+
+/* Cache invalidation occurs rarely, thus the LRU chain is not updated. It
+   fixes itself after a while. */
+
+void fat_cache_inval_inode(struct inode *inode)
+{
+	struct fat_cache *walk;
+
+	for (walk = fat_cache; walk; walk = walk->next)
+		if (walk->device == inode->i_dev
+		    && walk->ino == inode->i_ino)
+			walk->device = 0;
+}
+
+
+void fat_cache_inval_dev(kdev_t device)
+{
+	struct fat_cache *walk;
+
+	for (walk = fat_cache; walk; walk = walk->next)
+		if (walk->device == device)
+			walk->device = 0;
+}
+
+
+int get_cluster(struct inode *inode,int cluster)
+{
+	int nr,count;
+
+	if (!(nr = MSDOS_I(inode)->i_start)) return 0;
+	if (!cluster) return nr;
+	count = 0;
+	for (cache_lookup(inode,cluster,&count,&nr); count < cluster;
+	    count++) {
+		if ((nr = fat_access(inode->i_sb,nr,-1)) == -1) return 0;
+		if (!nr) return 0;
+	}
+	cache_add(inode,cluster,nr);
+	return nr;
+}
+
+
+int fat_smap(struct inode *inode,int sector)
+{
+	struct msdos_sb_info *sb;
+	int cluster,offset;
+
+	sb = MSDOS_SB(inode->i_sb);
+	if (inode->i_ino == MSDOS_ROOT_INO || (S_ISDIR(inode->i_mode) &&
+	    !MSDOS_I(inode)->i_start)) {
+		if (sector >= sb->dir_entries >> MSDOS_DPS_BITS) return 0;
+		return sector+sb->dir_start;
+	}
+	cluster = sector/sb->cluster_size;
+	offset = sector % sb->cluster_size;
+	if (!(cluster = get_cluster(inode,cluster))) return 0;
+	return (cluster-2)*sb->cluster_size+sb->data_start+offset;
+}
+
+
+/* Free all clusters after the skip'th cluster. Doesn't use the cache,
+   because this way we get an additional sanity check. */
+
+int fat_free(struct inode *inode,int skip)
+{
+	int nr,last;
+
+	if (!(nr = MSDOS_I(inode)->i_start)) return 0;
+	last = 0;
+	while (skip--) {
+		last = nr;
+		if ((nr = fat_access(inode->i_sb,nr,-1)) == -1) return 0;
+		if (!nr) {
+			printk("fat_free: skipped EOF\n");
+			return -EIO;
+		}
+	}
+	if (last)
+		fat_access(inode->i_sb,last,MSDOS_SB(inode->i_sb)->fat_bits ==
+		    12 ? 0xff8 : 0xfff8);
+	else {
+		MSDOS_I(inode)->i_start = 0;
+		inode->i_dirt = 1;
+	}
+	lock_fat(inode->i_sb);
+	while (nr != -1) {
+		if (!(nr = fat_access(inode->i_sb,nr,0))) {
+			fat_fs_panic(inode->i_sb,"fat_free: deleting beyond EOF");
+			break;
+		}
+		if (MSDOS_SB(inode->i_sb)->free_clusters != -1)
+			MSDOS_SB(inode->i_sb)->free_clusters++;
+		inode->i_blocks -= MSDOS_SB(inode->i_sb)->cluster_size;
+	}
+	unlock_fat(inode->i_sb);
+	fat_cache_inval_inode(inode);
+	return 0;
+}