[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: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

diff --git a/Documentation/md.txt b/Documentation/md.txt
index 0668f9dc9d29635393e5876b15b1a3bce9abaa13..084ecf4eb2f87d1c89f6943db0c5f5bfbef1f32e 100644 (file)
--- a/Documentation/md.txt
+++ b/Documentation/md.txt
@@ -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.
 
       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
 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 --git a/drivers/md/bitmap.c b/drivers/md/bitmap.c
index ecc56765d949ebc977ebbe5326b0dcc39197566e..0a44298fb3535bc2b5f7efae268387c065c130d1 100644 (file)
--- a/drivers/md/bitmap.c
+++ b/drivers/md/bitmap.c
@@ -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)
 {
 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)];
 }
 
        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);
        }
 
        page = filemap_get_page(bitmap, chunk);

+       if (!page) return;

        bit = file_page_offset(chunk);
 
        /* set the bit */
        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
  */
 /*
  * flush out any pending updates
  */

diff --git a/drivers/md/md.c b/drivers/md/md.c
index 8b08043f07ef09353c80dec4fd89f67bd03bbb6a..b95dd8a183ec9da71c0ab501f61577c770d3607f 100644 (file)
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -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 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)
 {
 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_sync_completed.attr,
        &md_suspend_lo.attr,
        &md_suspend_hi.attr,

+       &md_bitmap.attr,

        NULL,
 };
 static struct attribute_group md_redundancy_group = {
        NULL,
 };
 static struct attribute_group md_redundancy_group = {

diff --git a/include/linux/raid/bitmap.h b/include/linux/raid/bitmap.h
index 63df898fe2e95dcf092a3ac5dedeb76b431f8122..84d88775185556e4d2a8a6b0560bcfc9c202038a 100644 (file)
--- a/include/linux/raid/bitmap.h
+++ b/include/linux/raid/bitmap.h
@@ -265,6 +265,8 @@ int bitmap_update_sb(struct bitmap *bitmap);
 int  bitmap_setallbits(struct bitmap *bitmap);
 void bitmap_write_all(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);
 /* these are exported */
 int bitmap_startwrite(struct bitmap *bitmap, sector_t offset,
                        unsigned long sectors, int behind);