[dm-devel] [PATCH] dm-integrity: fix excessive alignment of metadata runs
Mikulas Patocka
mpatocka at redhat.com
Wed Nov 13 11:48:16 UTC 2019
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.
This patch fixes the bug by providing a proper 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.
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 at redhat.com>
---
Documentation/admin-guide/device-mapper/dm-integrity.rst | 5 ++
drivers/md/dm-integrity.c | 26 ++++++++++++---
2 files changed, 27 insertions(+), 4 deletions(-)
Index: linux-2.6/drivers/md/dm-integrity.c
===================================================================
--- linux-2.6.orig/drivers/md/dm-integrity.c 2019-11-12 21:13:57.000000000 +0100
+++ linux-2.6/drivers/md/dm-integrity.c 2019-11-13 12:29:00.000000000 +0100
@@ -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
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 d
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 d
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(struc
if (!ic->meta_dev) {
sector_t last_sector, last_area, last_offset;
+ /* 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 = 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;
+ 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
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_ta
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_ta
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_t
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,
Index: linux-2.6/Documentation/admin-guide/device-mapper/dm-integrity.rst
===================================================================
--- linux-2.6.orig/Documentation/admin-guide/device-mapper/dm-integrity.rst 2019-10-10 16:51:56.000000000 +0200
+++ linux-2.6/Documentation/admin-guide/device-mapper/dm-integrity.rst 2019-11-13 12:24:48.000000000 +0100
@@ -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
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