hpfs: support hotfixes

When the OS/2 driver hits a disk write error, it writes the sector to
another location and adds the sector mapping to the hotfix map.

This patch makes the hpfs driver understand the hotfix map and remap
accesses accoring to it.
Signed-off-by: Mikulas Patocka <mikulas@twibright.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/hpfs/buffer.c

@@ -10,6 +10,30 @@
 #include <linux/blkdev.h>
 #include "hpfs_fn.h"
 
+secno hpfs_search_hotfix_map(struct super_block *s, secno sec)
+{
+	unsigned i;
+	struct hpfs_sb_info *sbi = hpfs_sb(s);
+	for (i = 0; unlikely(i < sbi->n_hotfixes); i++) {
+		if (sbi->hotfix_from[i] == sec) {
+			return sbi->hotfix_to[i];
+		}
+	}
+	return sec;
+}
+
+unsigned hpfs_search_hotfix_map_for_range(struct super_block *s, secno sec, unsigned n)
+{
+	unsigned i;
+	struct hpfs_sb_info *sbi = hpfs_sb(s);
+	for (i = 0; unlikely(i < sbi->n_hotfixes); i++) {
+		if (sbi->hotfix_from[i] >= sec && sbi->hotfix_from[i] < sec + n) {
+			n = sbi->hotfix_from[i] - sec;
+		}
+	}
+	return n;
+}
+
 void hpfs_prefetch_sectors(struct super_block *s, unsigned secno, int n)
 {
 	struct buffer_head *bh;
@@ -18,6 +42,9 @@ void hpfs_prefetch_sectors(struct super_block *s, unsigned secno, int n)
 	if (n <= 0 || unlikely(secno >= hpfs_sb(s)->sb_fs_size))
 		return;
 
+	if (unlikely(hpfs_search_hotfix_map_for_range(s, secno, n) != n))
+		return;
+
 	bh = sb_find_get_block(s, secno);
 	if (bh) {
 		if (buffer_uptodate(bh)) {
@@ -51,7 +78,7 @@ void *hpfs_map_sector(struct super_block *s, unsigned secno, struct buffer_head
 
 	cond_resched();
 
-	*bhp = bh = sb_bread(s, secno);
+	*bhp = bh = sb_bread(s, hpfs_search_hotfix_map(s, secno));
 	if (bh != NULL)
 		return bh->b_data;
 	else {
@@ -71,7 +98,7 @@ void *hpfs_get_sector(struct super_block *s, unsigned secno, struct buffer_head
 
 	cond_resched();
 
-	if ((*bhp = bh = sb_getblk(s, secno)) != NULL) {
+	if ((*bhp = bh = sb_getblk(s, hpfs_search_hotfix_map(s, secno))) != NULL) {
 		if (!buffer_uptodate(bh)) wait_on_buffer(bh);
 		set_buffer_uptodate(bh);
 		return bh->b_data;
@@ -99,10 +126,10 @@ void *hpfs_map_4sectors(struct super_block *s, unsigned secno, struct quad_buffe
 
 	hpfs_prefetch_sectors(s, secno, 4 + ahead);
 
-	if (!(qbh->bh[0] = sb_bread(s, secno + 0))) goto bail0;
-	if (!(qbh->bh[1] = sb_bread(s, secno + 1))) goto bail1;
-	if (!(qbh->bh[2] = sb_bread(s, secno + 2))) goto bail2;
-	if (!(qbh->bh[3] = sb_bread(s, secno + 3))) goto bail3;
+	if (!hpfs_map_sector(s, secno + 0, &qbh->bh[0], 0)) goto bail0;
+	if (!hpfs_map_sector(s, secno + 1, &qbh->bh[1], 0)) goto bail1;
+	if (!hpfs_map_sector(s, secno + 2, &qbh->bh[2], 0)) goto bail2;
+	if (!hpfs_map_sector(s, secno + 3, &qbh->bh[3], 0)) goto bail3;
 
 	if (likely(qbh->bh[1]->b_data == qbh->bh[0]->b_data + 1 * 512) &&
 	    likely(qbh->bh[2]->b_data == qbh->bh[0]->b_data + 2 * 512) &&

fs/hpfs/file.c

@@ -83,6 +83,11 @@ static int hpfs_get_block(struct inode *inode, sector_t iblock, struct buffer_he
 	if (s) {
 		if (bh_result->b_size >> 9 < n_secs)
 			n_secs = bh_result->b_size >> 9;
+		n_secs = hpfs_search_hotfix_map_for_range(inode->i_sb, s, n_secs);
+		if (unlikely(!n_secs)) {
+			s = hpfs_search_hotfix_map(inode->i_sb, s);
+			n_secs = 1;
+		}
 		map_bh(bh_result, inode->i_sb, s);
 		bh_result->b_size = n_secs << 9;
 		goto ret_0;
@@ -101,7 +106,7 @@ static int hpfs_get_block(struct inode *inode, sector_t iblock, struct buffer_he
 	inode->i_blocks++;
 	hpfs_i(inode)->mmu_private += 512;
 	set_buffer_new(bh_result);
-	map_bh(bh_result, inode->i_sb, s);
+	map_bh(bh_result, inode->i_sb, hpfs_search_hotfix_map(inode->i_sb, s));
 	ret_0:
 	r = 0;
 	ret_r:
@@ -181,7 +186,7 @@ static int hpfs_write_end(struct file *file, struct address_space *mapping,
 
 static sector_t _hpfs_bmap(struct address_space *mapping, sector_t block)
 {
-	return generic_block_bmap(mapping,block,hpfs_get_block);
+	return generic_block_bmap(mapping, block, hpfs_get_block);
 }
 
 const struct address_space_operations hpfs_aops = {

fs/hpfs/hpfs_fn.h

@@ -88,6 +88,10 @@ struct hpfs_sb_info {
 	unsigned sb_max_fwd_alloc;	/* max forwad allocation */
 	int sb_timeshift;
 	struct rcu_head rcu;
+
+	unsigned n_hotfixes;
+	secno hotfix_from[256];
+	secno hotfix_to[256];
 };
 
 /* Four 512-byte buffers and the 2k block obtained by concatenating them */
@@ -217,6 +221,8 @@ void hpfs_remove_fnode(struct super_block *, fnode_secno fno);
 
 /* buffer.c */
 
+secno hpfs_search_hotfix_map(struct super_block *s, secno sec);
+unsigned hpfs_search_hotfix_map_for_range(struct super_block *s, secno sec, unsigned n);
 void hpfs_prefetch_sectors(struct super_block *, unsigned, int);
 void *hpfs_map_sector(struct super_block *, unsigned, struct buffer_head **, int);
 void *hpfs_get_sector(struct super_block *, unsigned, struct buffer_head **);
@@ -285,6 +291,7 @@ __le32 *hpfs_map_bitmap(struct super_block *, unsigned, struct quad_buffer_head
 void hpfs_prefetch_bitmap(struct super_block *, unsigned);
 unsigned char *hpfs_load_code_page(struct super_block *, secno);
 __le32 *hpfs_load_bitmap_directory(struct super_block *, secno bmp);
+void hpfs_load_hotfix_map(struct super_block *s, struct hpfs_spare_block *spareblock);
 struct fnode *hpfs_map_fnode(struct super_block *s, ino_t, struct buffer_head **);
 struct anode *hpfs_map_anode(struct super_block *s, anode_secno, struct buffer_head **);
 struct dnode *hpfs_map_dnode(struct super_block *s, dnode_secno, struct quad_buffer_head *);

fs/hpfs/map.c

@@ -130,6 +130,32 @@ __le32 *hpfs_load_bitmap_directory(struct super_block *s, secno bmp)
 	return b;
 }
 
+void hpfs_load_hotfix_map(struct super_block *s, struct hpfs_spare_block *spareblock)
+{
+	struct quad_buffer_head qbh;
+	u32 *directory;
+	u32 n_hotfixes, n_used_hotfixes;
+	unsigned i;
+
+	n_hotfixes = le32_to_cpu(spareblock->n_spares);
+	n_used_hotfixes = le32_to_cpu(spareblock->n_spares_used);
+
+	if (n_hotfixes > 256 || n_used_hotfixes > n_hotfixes) {
+		hpfs_error(s, "invalid number of hotfixes: %u, used: %u", n_hotfixes, n_used_hotfixes);
+		return;
+	}
+	if (!(directory = hpfs_map_4sectors(s, le32_to_cpu(spareblock->hotfix_map), &qbh, 0))) {
+		hpfs_error(s, "can't load hotfix map");
+		return;
+	}
+	for (i = 0; i < n_used_hotfixes; i++) {
+		hpfs_sb(s)->hotfix_from[i] = le32_to_cpu(directory[i]);
+		hpfs_sb(s)->hotfix_to[i] = le32_to_cpu(directory[n_hotfixes + i]);
+	}
+	hpfs_sb(s)->n_hotfixes = n_used_hotfixes;
+	hpfs_brelse4(&qbh);
+}
+
 /*
  * Load fnode to memory
  */

fs/hpfs/super.c

@@ -628,6 +628,9 @@ static int hpfs_fill_super(struct super_block *s, void *options, int silent)
 		goto bail4;
 	}
 
+	if (spareblock->n_spares_used)
+		hpfs_load_hotfix_map(s, spareblock);
+
 	/* Load bitmap directory */
 	if (!(sbi->sb_bmp_dir = hpfs_load_bitmap_directory(s, le32_to_cpu(superblock->bitmaps))))
 		goto bail4;
@@ -647,18 +650,6 @@ static int hpfs_fill_super(struct super_block *s, void *options, int silent)
 		mark_buffer_dirty(bh2);
 	}
 
-	if (spareblock->hotfixes_used || spareblock->n_spares_used) {
-		if (errs >= 2) {
-			pr_err("Hotfixes not supported here, try chkdsk\n");
-			mark_dirty(s, 0);
-			goto bail4;
-		}
-		hpfs_error(s, "hotfixes not supported here, try chkdsk");
-		if (errs == 0)
-			pr_err("Proceeding, but your filesystem will be probably corrupted by this driver...\n");
-		else
-			pr_err("This driver may read bad files or crash when operating on disk with hotfixes.\n");
-	}
 	if (le32_to_cpu(spareblock->n_dnode_spares) != le32_to_cpu(spareblock->n_dnode_spares_free)) {
 		if (errs >= 2) {
 			pr_err("Spare dnodes used, try chkdsk\n");