hpfs: remember free space

Previously, hpfs scanned all bitmaps each time the user asked for free
space using statfs. This patch changes it so that hpfs scans the
bitmaps only once, remembes the free space and on next invocation of
statfs it returns the value instantly.

New versions of wine are hammering on the statfs syscall very heavily,
making some games unplayable when they're stored on hpfs, with load
times in minutes.

This should be backported to the stable kernels because it fixes
user-visible problem (excessive level load times in wine).

Signed-off-by: Mikulas Patocka <[e-mail]>
Cc: [e-mail]
Signed-off-by: Linus Torvalds <[e-mail]>

fs/hpfs/alloc.c

···
 
 #include "hpfs_fn.h"
 
+static void hpfs_claim_alloc(struct super_block *s, secno sec)
+{
+	struct hpfs_sb_info *sbi = hpfs_sb(s);
+	if (sbi->sb_n_free != (unsigned)-1) {
+		if (unlikely(!sbi->sb_n_free)) {
+			hpfs_error(s, "free count underflow, allocating sector %08x", sec);
+			sbi->sb_n_free = -1;
+			return;
+		}
+		sbi->sb_n_free--;
+	}
+}
+
+static void hpfs_claim_free(struct super_block *s, secno sec)
+{
+	struct hpfs_sb_info *sbi = hpfs_sb(s);
+	if (sbi->sb_n_free != (unsigned)-1) {
+		if (unlikely(sbi->sb_n_free >= sbi->sb_fs_size)) {
+			hpfs_error(s, "free count overflow, freeing sector %08x", sec);
+			sbi->sb_n_free = -1;
+			return;
+		}
+		sbi->sb_n_free++;
+	}
+}
+
+static void hpfs_claim_dirband_alloc(struct super_block *s, secno sec)
+{
+	struct hpfs_sb_info *sbi = hpfs_sb(s);
+	if (sbi->sb_n_free_dnodes != (unsigned)-1) {
+		if (unlikely(!sbi->sb_n_free_dnodes)) {
+			hpfs_error(s, "dirband free count underflow, allocating sector %08x", sec);
+			sbi->sb_n_free_dnodes = -1;
+			return;
+		}
+		sbi->sb_n_free_dnodes--;
+	}
+}
+
+static void hpfs_claim_dirband_free(struct super_block *s, secno sec)
+{
+	struct hpfs_sb_info *sbi = hpfs_sb(s);
+	if (sbi->sb_n_free_dnodes != (unsigned)-1) {
+		if (unlikely(sbi->sb_n_free_dnodes >= sbi->sb_dirband_size / 4)) {
+			hpfs_error(s, "dirband free count overflow, freeing sector %08x", sec);
+			sbi->sb_n_free_dnodes = -1;
+			return;
+		}
+		sbi->sb_n_free_dnodes++;
+	}
+}
+
 /*
  * Check if a sector is allocated in bitmap
  * This is really slow. Turned on only if chk==2
···
 	}
 	sec = 0;
 	ret:
+	if (sec) {
+		i = 0;
+		do
+			hpfs_claim_alloc(s, sec + i);
+		while (unlikely(++i < n));
+	}
 	if (sec && f_p) {
 		for (i = 0; i < forward; i++) {
-			if (!hpfs_alloc_if_possible(s, sec + i + 1)) {
+			if (!hpfs_alloc_if_possible(s, sec + n + i)) {
 				hpfs_error(s, "Prealloc doesn't work! Wanted %d, allocated at %08x, can't allocate %d", forward, sec, i);
 				sec = 0;
 				break;
···
 	nr >>= 2;
 	sec = alloc_in_bmp(s, (~0x3fff) | nr, 1, 0);
 	if (!sec) return 0;
+	hpfs_claim_dirband_alloc(s, sec);
 	return ((sec & 0x3fff) << 2) + sbi->sb_dirband_start;
 }
 
···
 		bmp[(sec & 0x3fff) >> 5] &= cpu_to_le32(~(1 << (sec & 0x1f)));
 		hpfs_mark_4buffers_dirty(&qbh);
 		hpfs_brelse4(&qbh);
+		hpfs_claim_alloc(s, sec);
 		return 1;
 	}
 	hpfs_brelse4(&qbh);
···
 		return;
 	}
 	bmp[(sec & 0x3fff) >> 5] |= cpu_to_le32(1 << (sec & 0x1f));
+	hpfs_claim_free(s, sec);
 	if (!--n) {
 		hpfs_mark_4buffers_dirty(&qbh);
 		hpfs_brelse4(&qbh);
···
 		bmp[ssec >> 5] |= cpu_to_le32(1 << (ssec & 0x1f));
 		hpfs_mark_4buffers_dirty(&qbh);
 		hpfs_brelse4(&qbh);
+		hpfs_claim_dirband_free(s, dno);
 	}
 }
 
···
 			 dnode_secno *dno, struct quad_buffer_head *qbh)
 {
 	struct dnode *d;
-	if (hpfs_count_one_bitmap(s, hpfs_sb(s)->sb_dmap) > FREE_DNODES_ADD) {
+	if (hpfs_get_free_dnodes(s) > FREE_DNODES_ADD) {
 		if (!(*dno = alloc_in_dirband(s, near)))
 			if (!(*dno = hpfs_alloc_sector(s, near, 4, 0))) return NULL;
 	} else {

fs/hpfs/hpfs_fn.h

···
 __printf(2, 3)
 void hpfs_error(struct super_block *, const char *, ...);
 int hpfs_stop_cycles(struct super_block *, int, int *, int *, char *);
-unsigned hpfs_count_one_bitmap(struct super_block *, secno);
+unsigned hpfs_get_free_dnodes(struct super_block *);
 
 /*
  * local time (HPFS) to GMT (Unix)

fs/hpfs/super.c

···
 	call_rcu(&hpfs_sb(s)->rcu, lazy_free_sbi);
 }
 
-unsigned hpfs_count_one_bitmap(struct super_block *s, secno secno)
+static unsigned hpfs_count_one_bitmap(struct super_block *s, secno secno)
 {
 	struct quad_buffer_head qbh;
 	unsigned long *bits;
···
 
 	bits = hpfs_map_4sectors(s, secno, &qbh, 0);
 	if (!bits)
-		return 0;
+		return (unsigned)-1;
 	count = bitmap_weight(bits, 2048 * BITS_PER_BYTE);
 	hpfs_brelse4(&qbh);
 	return count;
···
 		hpfs_prefetch_bitmap(s, n);
 	}
 	for (n = 0; n < n_bands; n++) {
+		unsigned c;
 		hpfs_prefetch_bitmap(s, n + COUNT_RD_AHEAD);
-		count += hpfs_count_one_bitmap(s, le32_to_cpu(hpfs_sb(s)->sb_bmp_dir[n]));
+		c = hpfs_count_one_bitmap(s, le32_to_cpu(hpfs_sb(s)->sb_bmp_dir[n]));
+		if (c != (unsigned)-1)
+			count += c;
 	}
 	return count;
+}
+
+unsigned hpfs_get_free_dnodes(struct super_block *s)
+{
+	struct hpfs_sb_info *sbi = hpfs_sb(s);
+	if (sbi->sb_n_free_dnodes == (unsigned)-1) {
+		unsigned c = hpfs_count_one_bitmap(s, sbi->sb_dmap);
+		if (c == (unsigned)-1)
+			return 0;
+		sbi->sb_n_free_dnodes = c;
+	}
+	return sbi->sb_n_free_dnodes;
 }
 
 static int hpfs_statfs(struct dentry *dentry, struct kstatfs *buf)
···
 	struct super_block *s = dentry->d_sb;
 	struct hpfs_sb_info *sbi = hpfs_sb(s);
 	u64 id = huge_encode_dev(s->s_bdev->bd_dev);
+
 	hpfs_lock(s);
 
-	/*if (sbi->sb_n_free == -1) {*/
+	if (sbi->sb_n_free == (unsigned)-1)
 		sbi->sb_n_free = count_bitmaps(s);
-		sbi->sb_n_free_dnodes = hpfs_count_one_bitmap(s, sbi->sb_dmap);
-	/*}*/
+
 	buf->f_type = s->s_magic;
 	buf->f_bsize = 512;
 	buf->f_blocks = sbi->sb_fs_size;
 	buf->f_bfree = sbi->sb_n_free;
 	buf->f_bavail = sbi->sb_n_free;
 	buf->f_files = sbi->sb_dirband_size / 4;
-	buf->f_ffree = sbi->sb_n_free_dnodes;
+	buf->f_ffree = hpfs_get_free_dnodes(s);
 	buf->f_fsid.val[0] = (u32)id;
 	buf->f_fsid.val[1] = (u32)(id >> 32);
 	buf->f_namelen = 254;