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Subject[PATCH 001 of 3] md: Change md/bitmap file handling to use bmap to file blocks-fix

Fix problems with new bmap based access to bitmap files.

1/ When not using a file based bitmap, attach a NULL list of buffers
to each page so the common free_buffer routine can cope.
2/ Use submit_bh to read as well as write, rather than vfs_read.
This makes read and write more symetric.
3/ sync the file before reading, to ensure that the page cache has no
dirty pages that might get written out later.

Signed-off-by: Neil Brown <neilb@suse.de>

### Diffstat output
./drivers/md/bitmap.c | 46 ++++++++++++++++++++++------------------------
1 file changed, 22 insertions(+), 24 deletions(-)
diff ./drivers/md/bitmap.c~current~ ./drivers/md/bitmap.c
--- ./drivers/md/bitmap.c~current~ 2006-05-16 11:09:26.000000000 +1000
+++ ./drivers/md/bitmap.c 2006-05-16 11:09:33.000000000 +1000
@@ -247,6 +247,8 @@ static struct page *read_sb_page(mddev_t

if (sync_page_io(rdev->bdev, target, PAGE_SIZE, page, READ)) {
page->index = index;
+ attach_page_buffers(page, NULL); /* so that free_buffer will
+ * quietly no-op */
return page;
}
}
@@ -349,11 +351,8 @@ static struct page *read_page(struct fil
{
struct page *page = NULL;
struct inode *inode = file->f_dentry->d_inode;
- loff_t pos = index << PAGE_SHIFT;
- int ret;
struct buffer_head *bh;
sector_t block;
- mm_segment_t oldfs;

PRINTK("read bitmap file (%dB @ %Lu)\n", (int)PAGE_SIZE,
(unsigned long long)index << PAGE_SHIFT);
@@ -364,18 +363,6 @@ static struct page *read_page(struct fil
if (IS_ERR(page))
goto out;

- oldfs = get_fs();
- set_fs(KERNEL_DS);
- ret = vfs_read(file, (char __user*) page_address(page), count, &pos);
- set_fs(oldfs);
-
- if (ret >= 0 && ret != count)
- ret = -EIO;
- if (ret < 0) {
- put_page(page);
- page = ERR_PTR(ret);
- goto out;
- }
bh = alloc_page_buffers(page, 1<<inode->i_blkbits, 0);
if (!bh) {
put_page(page);
@@ -403,12 +390,22 @@ static struct page *read_page(struct fil

bh->b_end_io = end_bitmap_write;
bh->b_private = bitmap;
+ atomic_inc(&bitmap->pending_writes);
+ set_buffer_locked(bh);
+ set_buffer_mapped(bh);
+ submit_bh(READ, bh);
}
block++;
bh = bh->b_this_page;
}
-
page->index = index;
+
+ wait_event(bitmap->write_wait,
+ atomic_read(&bitmap->pending_writes)==0);
+ if (bitmap->flags & BITMAP_WRITE_ERROR) {
+ free_buffers(page);
+ page = ERR_PTR(-EIO);
+ }
out:
if (IS_ERR(page))
printk(KERN_ALERT "md: bitmap read error: (%dB @ %Lu): %ld\n",
@@ -1415,15 +1412,19 @@ int bitmap_create(mddev_t *mddev)
return -ENOMEM;

spin_lock_init(&bitmap->lock);
+ atomic_set(&bitmap->pending_writes, 0);
+ init_waitqueue_head(&bitmap->write_wait);
+
bitmap->mddev = mddev;

bitmap->file = file;
bitmap->offset = mddev->bitmap_offset;
- if (file) get_file(file);
-
- /* Ensure we read fresh data */
- invalidate_inode_pages(file->f_dentry->d_inode->i_mapping);
-
+ if (file) {
+ get_file(file);
+ do_sync_file_range(file, 0, LLONG_MAX,
+ SYNC_FILE_RANGE_WRITE |
+ SYNC_FILE_RANGE_WAIT_AFTER);
+ }
/* read superblock from bitmap file (this sets bitmap->chunksize) */
err = bitmap_read_sb(bitmap);
if (err)
@@ -1446,9 +1447,6 @@ int bitmap_create(mddev_t *mddev)

bitmap->syncchunk = ~0UL;

- atomic_set(&bitmap->pending_writes, 0);
- init_waitqueue_head(&bitmap->write_wait);
-
#ifdef INJECT_FATAL_FAULT_1
bitmap->bp = NULL;
#else
-
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