[dm-devel] [RFC, PATCH] dm-log.c: Work with devices with hard-sector-size > 512 bytes
Kevin Corry
kevcorry at us.ibm.com
Tue May 9 03:28:32 UTC 2006
On Tue March 28 2006 4:58 pm, Kevin Corry wrote:
> On Tue March 28 2006 9:01 am, Alasdair G Kergon wrote:
> > A couple of options:
> >
> > Retain the existing on-disk format exactly, but adjust the offsets and
> > sizes used in the reads and writes to avoid the problems (pre-reading
> > other data if necessary to extend a write).
>
> This method seems like it should be easy to implement. We could just extend
> the buffer for the disk-header and always read and write both the header
> and the log at the same time, and just point lc->clean_bits at the
> appropriate offset within that buffer. The log could then remain at offset
> 1k, and the version wouldn't have to change.
Sorry I haven't had a chance to get back to this in a while. I was finally
able to finish up a new patch to fix this bug based on the above suggestions.
This patch maintains compatibility with the existing metadata layout by
combining the disk-header buffer and clean-bits bitset buffer into a single
buffer.
--
Kevin Corry
kevcorry at us.ibm.com
http://www.ibm.com/linux/
http://evms.sourceforge.net/
On-disk logs for dm-mirror devices are currently hard-coded to use 512 byte
hard-sector-sizes. This patch fixes dm-log so it will work with devices
with non-512-byte hard-sector-sizes.
To maintain full compatibility, instead of moving the clean-bits bitset to a
different location, this patch removes the separate buffer used for the
bitset, and enlarges the disk-header buffer to encompass both the header and
the bitset. The I/O routines for the bitset are removed, and the I/O routines
for the disk-header now also read/write the bitset.
Signed-Off-By: Kevin Corry <kevcorry at us.ibm.com>
Index: 2.6.17-rc1/drivers/md/dm-log.c
===================================================================
--- 2.6.17-rc1.orig/drivers/md/dm-log.c
+++ 2.6.17-rc1/drivers/md/dm-log.c
@@ -155,8 +155,6 @@ struct log_c {
struct io_region header_location;
struct log_header *disk_header;
-
- struct io_region bits_location;
};
/*
@@ -241,29 +239,6 @@ static inline int write_header(struct lo
}
/*----------------------------------------------------------------
- * Bits IO
- *--------------------------------------------------------------*/
-static int read_bits(struct log_c *log)
-{
- int r;
- unsigned long ebits;
-
- r = dm_io_sync_vm(1, &log->bits_location, READ,
- log->clean_bits, &ebits);
- if (r)
- return r;
-
- return 0;
-}
-
-static int write_bits(struct log_c *log)
-{
- unsigned long ebits;
- return dm_io_sync_vm(1, &log->bits_location, WRITE,
- log->clean_bits, &ebits);
-}
-
-/*----------------------------------------------------------------
* core log constructor/destructor
*
* argv contains region_size followed optionally by [no]sync
@@ -373,9 +348,11 @@ static int disk_ctr(struct dirty_log *lo
unsigned int argc, char **argv)
{
int r;
- size_t size;
+ size_t size, bitset_size;
struct log_c *lc;
struct dm_dev *dev;
+ uint32_t *clean_bits;
+ unsigned int hardsect_size;
if (argc < 2 || argc > 3) {
DMWARN("wrong number of arguments to disk mirror log");
@@ -396,26 +373,30 @@ static int disk_ctr(struct dirty_log *lo
lc = (struct log_c *) log->context;
lc->log_dev = dev;
+ hardsect_size = ti->limits.hardsect_size;
+ bitset_size = lc->bitset_uint32_count * sizeof(uint32_t);
+
/* setup the disk header fields */
lc->header_location.bdev = lc->log_dev->bdev;
lc->header_location.sector = 0;
- lc->header_location.count = 1;
- /*
- * We can't read less than this amount, even though we'll
- * not be using most of this space.
- */
- lc->disk_header = vmalloc(1 << SECTOR_SHIFT);
+ /* Include both the header and the bitset in one buffer. */
+ size = dm_round_up((LOG_OFFSET << SECTOR_SHIFT) + bitset_size,
+ hardsect_size);
+ lc->header_location.count = size >> SECTOR_SHIFT;
+
+ lc->disk_header = vmalloc(size);
if (!lc->disk_header)
goto bad;
- /* setup the disk bitset fields */
- lc->bits_location.bdev = lc->log_dev->bdev;
- lc->bits_location.sector = LOG_OFFSET;
-
- size = dm_round_up(lc->bitset_uint32_count * sizeof(uint32_t),
- 1 << SECTOR_SHIFT);
- lc->bits_location.count = size >> SECTOR_SHIFT;
+ /* Deallocate the clean_bits buffer that was allocated in core_ctr()
+ * and point it at the appropriate place in the disk_header buffer.
+ */
+ clean_bits = lc->clean_bits;
+ lc->clean_bits = (void *)lc->disk_header + (LOG_OFFSET << SECTOR_SHIFT);
+ memcpy(lc->clean_bits, clean_bits, bitset_size);
+ vfree(clean_bits);
+
return 0;
bad:
@@ -429,6 +410,7 @@ static void disk_dtr(struct dirty_log *l
struct log_c *lc = (struct log_c *) log->context;
dm_put_device(lc->ti, lc->log_dev);
vfree(lc->disk_header);
+ lc->clean_bits = NULL;
core_dtr(log);
}
@@ -449,16 +431,11 @@ static int disk_resume(struct dirty_log
struct log_c *lc = (struct log_c *) log->context;
size_t size = lc->bitset_uint32_count * sizeof(uint32_t);
- /* read the disk header */
+ /* read the disk header and bitset */
r = read_header(lc);
if (r)
return r;
- /* read the bits */
- r = read_bits(lc);
- if (r)
- return r;
-
/* set or clear any new bits */
if (lc->sync == NOSYNC)
for (i = lc->header.nr_regions; i < lc->region_count; i++)
@@ -473,15 +450,10 @@ static int disk_resume(struct dirty_log
memcpy(lc->sync_bits, lc->clean_bits, size);
lc->sync_count = count_bits32(lc->clean_bits, lc->bitset_uint32_count);
- /* write the bits */
- r = write_bits(lc);
- if (r)
- return r;
-
/* set the correct number of regions in the header */
lc->header.nr_regions = lc->region_count;
- /* write the new header */
+ /* write the new header and bitset */
return write_header(lc);
}
@@ -518,7 +490,7 @@ static int disk_flush(struct dirty_log *
if (!lc->touched)
return 0;
- r = write_bits(lc);
+ r = write_header(lc);
if (!r)
lc->touched = 0;
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