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 <>
Signed-off-by: default avatarAndrew Morton <>
Signed-off-by: default avatarLinus Torvalds <>
parent 76186dd8
......@@ -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.
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
......@@ -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
......@@ -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 */
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[] = {
static struct attribute_group md_redundancy_group = {
......@@ -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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