Commit 9b1d1dac authored by Paul Clements's avatar Paul Clements Committed by Linus Torvalds
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[PATCH] md: new sysfs interface for setting bits in the write-intent-bitmap 



Add a new sysfs interface that allows the bitmap of an array to be dirtied.
The interface is write-only, and is used as follows:

echo "1000" > /sys/block/md2/md/bitmap

(dirty the bit for chunk 1000 [offset 0] in the in-memory and on-disk
bitmaps of array md2)

echo "1000-2000" > /sys/block/md1/md/bitmap

(dirty the bits for chunks 1000-2000 in md1's bitmap)

This is useful, for example, in cluster environments where you may need to
combine two disjoint bitmaps into one (following a server failure, after a
secondary server has taken over the array).  By combining the bitmaps on
the two servers, a full resync can be avoided (This was discussed on the
list back on March 18, 2005, "[PATCH 1/2] md bitmap bug fixes" thread).

Signed-off-by: default avatarNeil Brown <neilb@suse.de>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 76186dd8

Documentation/md.txt

+9 −0
Original line number Diff line number Diff line
@@ -410,6 +410,15 @@ also have 
      than sectors, this my be larger than the number of actual errors

      by a factor of the number of sectors in a page.



   bitmap_set_bits

      If the array has a write-intent bitmap, then writing to this

      attribute can set bits in the bitmap, indicating that a resync

      would need to check the corresponding blocks. Either individual

      numbers or start-end pairs can be written.  Multiple numbers

      can be separated by a space.

      Note that the numbers are 'bit' numbers, not 'block' numbers.

      They should be scaled by the bitmap_chunksize.



Each active md device may also have attributes specific to the

personality module that manages it.

These are specific to the implementation of the module and could

drivers/md/bitmap.c

+14 −0
Original line number Diff line number Diff line
@@ -613,6 +613,7 @@ static inline unsigned long file_page_offset(unsigned long chunk) 
static inline struct page *filemap_get_page(struct bitmap *bitmap,

					unsigned long chunk)

{

	if (file_page_index(chunk) >= bitmap->file_pages) return NULL;

	return bitmap->filemap[file_page_index(chunk) - file_page_index(0)];

}
@@ -739,6 +740,7 @@ static void bitmap_file_set_bit(struct bitmap *bitmap, sector_t block) 
	}



	page = filemap_get_page(bitmap, chunk);

	if (!page) return;

	bit = file_page_offset(chunk);



 	/* set the bit */
@@ -1322,6 +1324,18 @@ static void bitmap_set_memory_bits(struct bitmap *bitmap, sector_t offset, int n 


}



/* dirty the memory and file bits for bitmap chunks "s" to "e" */

void bitmap_dirty_bits(struct bitmap *bitmap, unsigned long s, unsigned long e)

{

	unsigned long chunk;



	for (chunk = s; chunk <= e; chunk++) {

		sector_t sec = chunk << CHUNK_BLOCK_SHIFT(bitmap);

		bitmap_set_memory_bits(bitmap, sec, 1);

		bitmap_file_set_bit(bitmap, sec);

	}

}



/*

 * flush out any pending updates

 */

drivers/md/md.c

+31 −0
Original line number Diff line number Diff line
@@ -2523,6 +2523,36 @@ new_dev_store(mddev_t *mddev, const char *buf, size_t len) 
static struct md_sysfs_entry md_new_device =

__ATTR(new_dev, S_IWUSR, null_show, new_dev_store);



static ssize_t

bitmap_store(mddev_t *mddev, const char *buf, size_t len)

{

	char *end;

	unsigned long chunk, end_chunk;



	if (!mddev->bitmap)

		goto out;

	/* buf should be <chunk> <chunk> ... or <chunk>-<chunk> ... (range) */

	while (*buf) {

		chunk = end_chunk = simple_strtoul(buf, &end, 0);

		if (buf == end) break;

		if (*end == '-') { /* range */

			buf = end + 1;

			end_chunk = simple_strtoul(buf, &end, 0);

			if (buf == end) break;

		}

		if (*end && !isspace(*end)) break;

		bitmap_dirty_bits(mddev->bitmap, chunk, end_chunk);

		buf = end;

		while (isspace(*buf)) buf++;

	}

	bitmap_unplug(mddev->bitmap); /* flush the bits to disk */

out:

	return len;

}



static struct md_sysfs_entry md_bitmap =

__ATTR(bitmap_set_bits, S_IWUSR, null_show, bitmap_store);



static ssize_t

size_show(mddev_t *mddev, char *page)

{
@@ -2843,6 +2873,7 @@ static struct attribute *md_redundancy_attrs[] = { 
	&md_sync_completed.attr,

	&md_suspend_lo.attr,

	&md_suspend_hi.attr,

	&md_bitmap.attr,

	NULL,

};

static struct attribute_group md_redundancy_group = {

include/linux/raid/bitmap.h

+2 −0
Original line number Diff line number Diff line
@@ -265,6 +265,8 @@ int bitmap_update_sb(struct bitmap *bitmap); 
int  bitmap_setallbits(struct bitmap *bitmap);

void bitmap_write_all(struct bitmap *bitmap);



void bitmap_dirty_bits(struct bitmap *bitmap, unsigned long s, unsigned long e);



/* these are exported */

int bitmap_startwrite(struct bitmap *bitmap, sector_t offset,

			unsigned long sectors, int behind);

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