[PATCH] md: allow md intent bitmap to be stored near the superblock.

This provides an alternate to storing the bitmap in a separate file.  The
bitmap can be stored at a given offset from the superblock.  Obviously the
creator of the array must make sure this doesn't intersect with data....
After is good for version-0.90 superblocks.

Signed-off-by: Neil Brown <neilb@cse.unsw.edu.au>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 106 insertions, 26 deletions

diff --git a/drivers/md/bitmap.c b/drivers/md/bitmap.c
index 204564dc6a0d..030d6861051a 100644
--- a/drivers/md/bitmap.c
+++ b/drivers/md/bitmap.c
@@ -116,7 +116,7 @@ static unsigned char *bitmap_alloc_page(struct bitmap *bitmap)
         if (!page)
                 printk("%s: bitmap_alloc_page FAILED\n", bmname(bitmap));
         else
-                printk("%s: bitmap_alloc_page: allocated page at %p\n",
+                PRINTK("%s: bitmap_alloc_page: allocated page at %p\n",
                         bmname(bitmap), page);
         return page;
 }
@@ -258,13 +258,61 @@ char *file_path(struct file *file, char *buf, int count)
  * basic page I/O operations
  */
 
+/* IO operations when bitmap is stored near all superblocks */
+static struct page *read_sb_page(mddev_t *mddev, long offset, unsigned long index)
+{
+        /* choose a good rdev and read the page from there */
+
+        mdk_rdev_t *rdev;
+        struct list_head *tmp;
+        struct page *page = alloc_page(GFP_KERNEL);
+        sector_t target;
+
+        if (!page)
+                return ERR_PTR(-ENOMEM);
+        do {
+                ITERATE_RDEV(mddev, rdev, tmp)
+                        if (rdev->in_sync && !rdev->faulty)
+                                goto found;
+                return ERR_PTR(-EIO);
+
+        found:
+                target = (rdev->sb_offset << 1) + offset + index * (PAGE_SIZE/512);
+
+        } while (!sync_page_io(rdev->bdev, target, PAGE_SIZE, page, READ));
+
+        page->index = index;
+        return page;
+}
+
+static int write_sb_page(mddev_t *mddev, long offset, struct page *page, int wait)
+{
+        mdk_rdev_t *rdev;
+        struct list_head *tmp;
+
+        ITERATE_RDEV(mddev, rdev, tmp)
+                if (rdev->in_sync && !rdev->faulty)
+                        md_super_write(mddev, rdev,
+                                       (rdev->sb_offset<<1) + offset
+                                       + page->index * (PAGE_SIZE/512),
+                                       PAGE_SIZE,
+                                       page);
+
+        if (wait)
+                wait_event(mddev->sb_wait, atomic_read(&mddev->pending_writes)==0);
+        return 0;
+}
+
 /*
- * write out a page
+ * write out a page to a file
  */
 static int write_page(struct bitmap *bitmap, struct page *page, int wait)
 {
         int ret = -ENOMEM;
 
+        if (bitmap->file == NULL)
+                return write_sb_page(bitmap->mddev, bitmap->offset, page, wait);
+
         lock_page(page);
 
         ret = page->mapping->a_ops->prepare_write(NULL, page, 0, PAGE_SIZE);
@@ -394,7 +442,12 @@ static int bitmap_read_sb(struct bitmap *bitmap)
         int err = -EINVAL;
 
         /* page 0 is the superblock, read it... */
-        bitmap->sb_page = read_page(bitmap->file, 0, &bytes_read);
+        if (bitmap->file)
+                bitmap->sb_page = read_page(bitmap->file, 0, &bytes_read);
+        else {
+                bitmap->sb_page = read_sb_page(bitmap->mddev, bitmap->offset, 0);
+                bytes_read = PAGE_SIZE;
+        }
         if (IS_ERR(bitmap->sb_page)) {
                 err = PTR_ERR(bitmap->sb_page);
                 bitmap->sb_page = NULL;
@@ -625,14 +678,16 @@ static void bitmap_file_kick(struct bitmap *bitmap)
         bitmap_mask_state(bitmap, BITMAP_STALE, MASK_SET);
         bitmap_update_sb(bitmap);
 
-        path = kmalloc(PAGE_SIZE, GFP_KERNEL);
-        if (path)
-                ptr = file_path(bitmap->file, path, PAGE_SIZE);
+        if (bitmap->file) {
+                path = kmalloc(PAGE_SIZE, GFP_KERNEL);
+                if (path)
+                        ptr = file_path(bitmap->file, path, PAGE_SIZE);
 
-        printk(KERN_ALERT "%s: kicking failed bitmap file %s from array!\n",
-                bmname(bitmap), ptr ? ptr : "");
+                printk(KERN_ALERT "%s: kicking failed bitmap file %s from array!\n",
+                       bmname(bitmap), ptr ? ptr : "");
 
-        kfree(path);
+                kfree(path);
+        }
 
         bitmap_file_put(bitmap);
 
@@ -676,7 +731,7 @@ static void bitmap_file_set_bit(struct bitmap *bitmap, sector_t block)
         void *kaddr;
         unsigned long chunk = block >> CHUNK_BLOCK_SHIFT(bitmap);
 
-        if (!bitmap->file || !bitmap->filemap) {
+        if (!bitmap->filemap) {
                 return;
         }
 
@@ -715,7 +770,7 @@ int bitmap_unplug(struct bitmap *bitmap)
          * flushed out to disk */
         for (i = 0; i < bitmap->file_pages; i++) {
                 spin_lock_irqsave(&bitmap->lock, flags);
-                if (!bitmap->file || !bitmap->filemap) {
+                if (!bitmap->filemap) {
                         spin_unlock_irqrestore(&bitmap->lock, flags);
                         return 0;
                 }
@@ -732,11 +787,15 @@ int bitmap_unplug(struct bitmap *bitmap)
                                 return 1;
         }
         if (wait) { /* if any writes were performed, we need to wait on them */
-                spin_lock_irq(&bitmap->write_lock);
-                wait_event_lock_irq(bitmap->write_wait,
-                        list_empty(&bitmap->complete_pages), bitmap->write_lock,
-                        wake_up_process(bitmap->writeback_daemon->tsk));
-                spin_unlock_irq(&bitmap->write_lock);
+                if (bitmap->file) {
+                        spin_lock_irq(&bitmap->write_lock);
+                        wait_event_lock_irq(bitmap->write_wait,
+                                            list_empty(&bitmap->complete_pages), bitmap->write_lock,
+                                            wake_up_process(bitmap->writeback_daemon->tsk));
+                        spin_unlock_irq(&bitmap->write_lock);
+                } else
+                        wait_event(bitmap->mddev->sb_wait,
+                                   atomic_read(&bitmap->mddev->pending_writes)==0);
         }
         return 0;
 }
@@ -764,7 +823,7 @@ static int bitmap_init_from_disk(struct bitmap *bitmap, int in_sync)
         chunks = bitmap->chunks;
         file = bitmap->file;
 
-        BUG_ON(!file);
+        BUG_ON(!file && !bitmap->offset);
 
 #if INJECT_FAULTS_3
         outofdate = 1;
@@ -779,7 +838,7 @@ static int bitmap_init_from_disk(struct bitmap *bitmap, int in_sync)
 
         num_pages = (bytes + sizeof(bitmap_super_t) + PAGE_SIZE - 1) / PAGE_SIZE;
 
-        if (i_size_read(file->f_mapping->host) < bytes + sizeof(bitmap_super_t)) {
+        if (file && i_size_read(file->f_mapping->host) < bytes + sizeof(bitmap_super_t)) {
                 printk(KERN_INFO "%s: bitmap file too short %lu < %lu\n",
                         bmname(bitmap),
                         (unsigned long) i_size_read(file->f_mapping->host),
@@ -816,14 +875,18 @@ static int bitmap_init_from_disk(struct bitmap *bitmap, int in_sync)
                                  */
                                 page = bitmap->sb_page;
                                 offset = sizeof(bitmap_super_t);
-                        } else {
+                        } else if (file) {
                                 page = read_page(file, index, &dummy);
-                                if (IS_ERR(page)) { /* read error */
-                                        ret = PTR_ERR(page);
-                                        goto out;
-                                }
+                                offset = 0;
+                        } else {
+                                page = read_sb_page(bitmap->mddev, bitmap->offset, index);
                                 offset = 0;
                         }
+                        if (IS_ERR(page)) { /* read error */
+                                ret = PTR_ERR(page);
+                                goto out;
+                        }
+
                         oldindex = index;
                         oldpage = page;
                         kmap(page);
@@ -874,6 +937,19 @@ out:
         return ret;
 }
 
+void bitmap_write_all(struct bitmap *bitmap)
+{
+        /* We don't actually write all bitmap blocks here,
+         * just flag them as needing to be written
+         */
+
+        unsigned long chunks = bitmap->chunks;
+        unsigned long bytes = (chunks+7)/8 + sizeof(bitmap_super_t);
+        unsigned long num_pages = (bytes + PAGE_SIZE-1) / PAGE_SIZE;
+        while (num_pages--)
+                bitmap->filemap_attr[num_pages] |= BITMAP_PAGE_NEEDWRITE;
+}
+
 
 static void bitmap_count_page(struct bitmap *bitmap, sector_t offset, int inc)
 {
@@ -913,7 +989,7 @@ int bitmap_daemon_work(struct bitmap *bitmap)
         for (j = 0; j < bitmap->chunks; j++) {
                 bitmap_counter_t *bmc;
                 spin_lock_irqsave(&bitmap->lock, flags);
-                if (!bitmap->file || !bitmap->filemap) {
+                if (!bitmap->filemap) {
                         /* error or shutdown */
                         spin_unlock_irqrestore(&bitmap->lock, flags);
                         break;
@@ -1072,6 +1148,7 @@ static int bitmap_start_daemon(struct bitmap *bitmap, mdk_thread_t **ptr,
 
         spin_lock_irqsave(&bitmap->lock, flags);
         *ptr = NULL;
+
         if (!bitmap->file) /* no need for daemon if there's no backing file */
                 goto out_unlock;
 
@@ -1416,9 +1493,11 @@ int bitmap_create(mddev_t *mddev)
 
         BUG_ON(sizeof(bitmap_super_t) != 256);
 
-        if (!file) /* bitmap disabled, nothing to do */
+        if (!file && !mddev->bitmap_offset) /* bitmap disabled, nothing to do */
                 return 0;
 
+        BUG_ON(file && mddev->bitmap_offset);
+
         bitmap = kmalloc(sizeof(*bitmap), GFP_KERNEL);
         if (!bitmap)
                 return -ENOMEM;
@@ -1438,7 +1517,8 @@ int bitmap_create(mddev_t *mddev)
                 return -ENOMEM;
 
         bitmap->file = file;
-        get_file(file);
+        bitmap->offset = mddev->bitmap_offset;
+        if (file) get_file(file);
         /* read superblock from bitmap file (this sets bitmap->chunksize) */
         err = bitmap_read_sb(bitmap);
         if (err)