2 files changed, 10 insertions, 1 deletions

diff --git a/drivers/md/bitmap.c b/drivers/md/bitmap.c
index 8f681da00277..15dbe03117e4 100644
--- a/drivers/md/bitmap.c
+++ b/drivers/md/bitmap.c
@@ -423,6 +423,8 @@ void bitmap_update_sb(struct bitmap *bitmap)
         /* This might have been changed by a reshape */
         sb->sync_size = cpu_to_le64(bitmap->mddev->resync_max_sectors);
         sb->chunksize = cpu_to_le32(bitmap->mddev->bitmap_info.chunksize);
+        sb->sectors_reserved = cpu_to_le32(bitmap->mddev->
+                                           bitmap_info.space);
         kunmap_atomic(sb);
         write_page(bitmap, bitmap->storage.sb_page, 1);
 }
@@ -536,6 +538,7 @@ static int bitmap_read_sb(struct bitmap *bitmap)
         bitmap_super_t *sb;
         unsigned long chunksize, daemon_sleep, write_behind;
         unsigned long long events;
+        unsigned long sectors_reserved = 0;
         int err = -EINVAL;
         struct page *sb_page;
 
@@ -573,6 +576,7 @@ static int bitmap_read_sb(struct bitmap *bitmap)
         chunksize = le32_to_cpu(sb->chunksize);
         daemon_sleep = le32_to_cpu(sb->daemon_sleep) * HZ;
         write_behind = le32_to_cpu(sb->write_behind);
+        sectors_reserved = le32_to_cpu(sb->sectors_reserved);
 
         /* verify that the bitmap-specific fields are valid */
         if (sb->magic != cpu_to_le32(BITMAP_MAGIC))
@@ -633,6 +637,9 @@ out_no_sb:
         bitmap->mddev->bitmap_info.chunksize = chunksize;
         bitmap->mddev->bitmap_info.daemon_sleep = daemon_sleep;
         bitmap->mddev->bitmap_info.max_write_behind = write_behind;
+        if (bitmap->mddev->bitmap_info.space == 0 ||
+            bitmap->mddev->bitmap_info.space > sectors_reserved)
+                bitmap->mddev->bitmap_info.space = sectors_reserved;
         if (err)
                 bitmap_print_sb(bitmap);
         return err;
diff --git a/drivers/md/bitmap.h b/drivers/md/bitmap.h
index 04dcde3871be..df4aeb6ac6f0 100644
--- a/drivers/md/bitmap.h
+++ b/drivers/md/bitmap.h
@@ -128,8 +128,10 @@ typedef struct bitmap_super_s {
         __le32 chunksize;    /* 52  the bitmap chunk size in bytes */
         __le32 daemon_sleep; /* 56  seconds between disk flushes */
         __le32 write_behind; /* 60  number of outstanding write-behind writes */
+        __le32 sectors_reserved; /* 64 number of 512-byte sectors that are
+                                  * reserved for the bitmap. */
 
-        __u8  pad[256 - 64]; /* set to zero */
+        __u8  pad[256 - 68]; /* set to zero */
 } bitmap_super_t;
 
 /* notes: