dm integrity: fix excessive alignment of metadata runs

Metadata runs are supposed to be aligned on 4k boundary (so that they work
efficiently with disks with 4k sectors). However, there was a programming
bug that makes them aligned on 128k boundary instead. The unused space is
wasted.

Fix this bug by providing a proper 4k alignment. In order to keep
existing volumes working, we introduce a new flag SB_FLAG_FIXED_PADDING
- when the flag is clear, we calculate the padding the old way. In order
to make sure that the old version cannot mount the volume created by the
new version, we increase superblock version to 4.

Also in order to not break with old integritysetup, we fix alignment
only if the parameter "fix_padding" is present when formatting the
device.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>

Documentation/admin-guide/device-mapper/dm-integrity.rst

@@ -177,6 +177,11 @@ bitmap_flush_interval:number
 	The bitmap flush interval in milliseconds. The metadata buffers
 	are synchronized when this interval expires.
 
+fix_padding
+	Use a smaller padding of the tag area that is more
+	space-efficient. If this option is not present, large padding is
+	used - that is for compatibility with older kernels.
+
 
 The journal mode (D/J), buffer_sectors, journal_watermark, commit_time can
 be changed when reloading the target (load an inactive table and swap the

drivers/md/dm-integrity.c

@@ -53,6 +53,7 @@
 #define SB_VERSION_1			1
 #define SB_VERSION_2			2
 #define SB_VERSION_3			3
+#define SB_VERSION_4			4
 #define SB_SECTORS			8
 #define MAX_SECTORS_PER_BLOCK		8
 
@@ -73,6 +74,7 @@ struct superblock {
 #define SB_FLAG_HAVE_JOURNAL_MAC	0x1
 #define SB_FLAG_RECALCULATING		0x2
 #define SB_FLAG_DIRTY_BITMAP		0x4
+#define SB_FLAG_FIXED_PADDING		0x8
 
 #define	JOURNAL_ENTRY_ROUNDUP		8
 
@@ -250,6 +252,7 @@ struct dm_integrity_c {
 	bool journal_uptodate;
 	bool just_formatted;
 	bool recalculate_flag;
+	bool fix_padding;
 
 	struct alg_spec internal_hash_alg;
 	struct alg_spec journal_crypt_alg;
@@ -463,7 +466,9 @@ static void wraparound_section(struct dm_integrity_c *ic, unsigned *sec_ptr)
 
 static void sb_set_version(struct dm_integrity_c *ic)
 {
-	if (ic->mode == 'B' || ic->sb->flags & cpu_to_le32(SB_FLAG_DIRTY_BITMAP))
+	if (ic->sb->flags & cpu_to_le32(SB_FLAG_FIXED_PADDING))
+		ic->sb->version = SB_VERSION_4;
+	else if (ic->mode == 'B' || ic->sb->flags & cpu_to_le32(SB_FLAG_DIRTY_BITMAP))
 		ic->sb->version = SB_VERSION_3;
 	else if (ic->meta_dev || ic->sb->flags & cpu_to_le32(SB_FLAG_RECALCULATING))
 		ic->sb->version = SB_VERSION_2;
@@ -2955,6 +2960,7 @@ static void dm_integrity_status(struct dm_target *ti, status_type_t type,
 		arg_count += !!ic->internal_hash_alg.alg_string;
 		arg_count += !!ic->journal_crypt_alg.alg_string;
 		arg_count += !!ic->journal_mac_alg.alg_string;
+		arg_count += (ic->sb->flags & cpu_to_le32(SB_FLAG_FIXED_PADDING)) != 0;
 		DMEMIT("%s %llu %u %c %u", ic->dev->name, (unsigned long long)ic->start,
 		       ic->tag_size, ic->mode, arg_count);
 		if (ic->meta_dev)
@@ -2974,6 +2980,8 @@ static void dm_integrity_status(struct dm_target *ti, status_type_t type,
 			DMEMIT(" sectors_per_bit:%llu", (unsigned long long)ic->sectors_per_block << ic->log2_blocks_per_bitmap_bit);
 			DMEMIT(" bitmap_flush_interval:%u", jiffies_to_msecs(ic->bitmap_flush_interval));
 		}
+		if ((ic->sb->flags & cpu_to_le32(SB_FLAG_FIXED_PADDING)) != 0)
+			DMEMIT(" fix_padding");
 
 #define EMIT_ALG(a, n)							\
 		do {							\
@@ -3042,8 +3050,14 @@ static int calculate_device_limits(struct dm_integrity_c *ic)
 	if (!ic->meta_dev) {
 		sector_t last_sector, last_area, last_offset;
 
-		ic->metadata_run = roundup((__u64)ic->tag_size << (ic->sb->log2_interleave_sectors - ic->sb->log2_sectors_per_block),
-					   (__u64)(1 << SECTOR_SHIFT << METADATA_PADDING_SECTORS)) >> SECTOR_SHIFT;
+		/* we have to maintain excessive padding for compatibility with existing volumes */
+		__u64 metadata_run_padding =
+			ic->sb->flags & cpu_to_le32(SB_FLAG_FIXED_PADDING) ?
+			(__u64)(METADATA_PADDING_SECTORS << SECTOR_SHIFT) :
+			(__u64)(1 << SECTOR_SHIFT << METADATA_PADDING_SECTORS);
+
+		ic->metadata_run = round_up((__u64)ic->tag_size << (ic->sb->log2_interleave_sectors - ic->sb->log2_sectors_per_block),
+					    metadata_run_padding) >> SECTOR_SHIFT;
 		if (!(ic->metadata_run & (ic->metadata_run - 1)))
 			ic->log2_metadata_run = __ffs(ic->metadata_run);
 		else
@@ -3086,6 +3100,8 @@ static int initialize_superblock(struct dm_integrity_c *ic, unsigned journal_sec
 		journal_sections = 1;
 
 	if (!ic->meta_dev) {
+		if (ic->fix_padding)
+			ic->sb->flags |= cpu_to_le32(SB_FLAG_FIXED_PADDING);
 		ic->sb->journal_sections = cpu_to_le32(journal_sections);
 		if (!interleave_sectors)
 			interleave_sectors = DEFAULT_INTERLEAVE_SECTORS;
@@ -3725,6 +3741,8 @@ static int dm_integrity_ctr(struct dm_target *ti, unsigned argc, char **argv)
 				goto bad;
 		} else if (!strcmp(opt_string, "recalculate")) {
 			ic->recalculate_flag = true;
+		} else if (!strcmp(opt_string, "fix_padding")) {
+			ic->fix_padding = true;
 		} else {
 			r = -EINVAL;
 			ti->error = "Invalid argument";
@@ -3867,7 +3885,7 @@ static int dm_integrity_ctr(struct dm_target *ti, unsigned argc, char **argv)
 			should_write_sb = true;
 	}
 
-	if (!ic->sb->version || ic->sb->version > SB_VERSION_3) {
+	if (!ic->sb->version || ic->sb->version > SB_VERSION_4) {
 		r = -EINVAL;
 		ti->error = "Unknown version";
 		goto bad;
@@ -4182,7 +4200,7 @@ static void dm_integrity_dtr(struct dm_target *ti)
 
 static struct target_type integrity_target = {
 	.name			= "integrity",
-	.version		= {1, 3, 0},
+	.version		= {1, 4, 0},
 	.module			= THIS_MODULE,
 	.features		= DM_TARGET_SINGLETON | DM_TARGET_INTEGRITY,
 	.ctr			= dm_integrity_ctr,