From: Paul Clements <[email protected]>
This patch (tested against 2.6.18-rc1-mm1) adds 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: Neil Brown <[email protected]>
### Diffstat output
./Documentation/md.txt | 9 +++++++++
./drivers/md/bitmap.c | 14 ++++++++++++++
./drivers/md/md.c | 31 +++++++++++++++++++++++++++++++
./include/linux/raid/bitmap.h | 2 ++
4 files changed, 56 insertions(+)
diff .prev/Documentation/md.txt ./Documentation/md.txt
--- .prev/Documentation/md.txt 2006-08-24 17:23:45.000000000 +1000
+++ ./Documentation/md.txt 2006-08-24 17:24:05.000000000 +1000
@@ -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
diff .prev/drivers/md/bitmap.c ./drivers/md/bitmap.c
--- .prev/drivers/md/bitmap.c 2006-08-24 17:23:45.000000000 +1000
+++ ./drivers/md/bitmap.c 2006-08-24 17:24:05.000000000 +1000
@@ -613,6 +613,7 @@ static inline unsigned long file_page_of
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 b
}
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(struc
}
+/* 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
*/
diff .prev/drivers/md/md.c ./drivers/md/md.c
--- .prev/drivers/md/md.c 2006-08-24 17:23:45.000000000 +1000
+++ ./drivers/md/md.c 2006-08-24 17:24:05.000000000 +1000
@@ -2524,6 +2524,36 @@ static struct md_sysfs_entry md_new_devi
__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)
{
return sprintf(page, "%llu\n", (unsigned long long)mddev->size);
@@ -2843,6 +2873,7 @@ static struct attribute *md_redundancy_a
&md_sync_completed.attr,
&md_suspend_lo.attr,
&md_suspend_hi.attr,
+ &md_bitmap.attr,
NULL,
};
static struct attribute_group md_redundancy_group = {
diff .prev/include/linux/raid/bitmap.h ./include/linux/raid/bitmap.h
--- .prev/include/linux/raid/bitmap.h 2006-08-24 17:23:45.000000000 +1000
+++ ./include/linux/raid/bitmap.h 2006-08-24 17:24:05.000000000 +1000
@@ -265,6 +265,8 @@ int bitmap_update_sb(struct bitmap *bitm
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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