ext4: Update i_diskzie during writepage for delayed allocation.

ext4_ext_get_blocks returns number of blocks allocated with buffer head unmapped for a read from prealloc space. This is needed so that delayed allocation doesn't do block reservation for prealloc space since the blocks are already resevred on disk. Fix ext4_ext_get_blocks to not return greater than max_blocks and also mark the buffer head unwritten. Some code path tries to read the block if buffer_head is not new and no uptodate. Marking the buffer head unwritten avoid this reading.

Signed-off-by Aneesh Kumar K.V <[email protected]>

---
 fs/ext4/extents.c |   14 +++++++++++++-
 1 files changed, 13 insertions(+), 1 deletions(-)

fs/ext4/extents.c +13 -1

index d6ae40a..edd1bf2 100644
@@ -2600,8 +2600,20 @@ int ext4_ext_get_blocks(handle_t *handle, struct inode *inode,
 			}
 			if (create == EXT4_CREATE_UNINITIALIZED_EXT)
 				goto out;
-			if (!create)
+			if (!create) {
+				/*
+				 * We have blocks reserved already. We
+				 * return allocated blocks so that delalloc
+				 * won't do block reservation for us. But
+				 * the buffer head will be unmapped so that
+				 * a read from the block return 0
+				 */
+				if (allocated > max_blocks)
+					allocated = max_blocks;
+				/* mark the buffer unwritten */
+				__set_bit(BH_Unwritten, &bh_result->b_state);
 				goto out2;
+			}
 
 			ret = ext4_ext_convert_to_initialized(handle, inode,
 								path, iblock,

Quoted 8 lines · Aneesh Kumar K.V

ext4_ext_get_blocks returns number of blocks allocated with buffer head unmapped for a read from prealloc space. This is needed so that delayed allocation doesn't do block reservation for prealloc space since the blocks are already resevred on disk. Fix ext4_ext_get_blocks to not return greater than max_blocks and also mark the buffer head unwritten. Some code path tries to read the block if buffer_head is not new and no uptodate. Marking the buffer head unwritten avoid this reading.

Seems this patch fixes two bugs together, it would be nice to split to two as they cause two different problems.

To fix the bh->b_size warning solof founds for delayed allocation, I would say we need to fix it in ext4_get_blocks_handle() (for indirect files) and ext4_ext_get_blocks()(for extent files) both, not allowing returning b_size greater than what the caller asking for. Also, the patch below seems only address the preallocation map case, we need to fix in in general block lookup case.

Quoted 10 lines · Mingming Cao

Quoted 8 lines · Aneesh Kumar K.V

ext4_ext_get_blocks returns number of blocks allocated with buffer head unmapped for a read from prealloc space. This is needed so that delayed allocation doesn't do block reservation for prealloc space since the blocks are already resevred on disk. Fix ext4_ext_get_blocks to not return greater than max_blocks and also mark the buffer head unwritten. Some code path tries to read the block if buffer_head is not new and no uptodate. Marking the buffer head unwritten avoid this reading.

Quoted 2 lines

Seems this patch fixes two bugs together, it would be nice to split to two as they cause two different problems.

Split patches here.

http://www.radian.org/~kvaneesh/ext4/patches-to-patchqueue/

Quoted 8 lines

To fix the bh->b_size warning solof founds for delayed allocation, I would say we need to fix it in ext4_get_blocks_handle() (for indirect files) and ext4_ext_get_blocks()(for extent files) both, not allowing returning b_size greater than what the caller asking for. Also, the patch below seems only address the preallocation map case, we need to fix in in general block lookup case.

ext4_ext_get_blocks already make sure we doesn't return > max_blocks. for normal allocation.

2694 out:
2695 if (allocated > max_blocks)
2696 allocated = max_blocks;

-aneesh

We need to update i_disksize after allocating blocks. writepages already does this. Update writepage to also update i_disksize.

Signed-off-by Aneesh Kumar K.V <[email protected]>

---
 fs/ext4/inode.c |   40 +++++++++++++++++++++++++++++++++++++++-
 1 files changed, 39 insertions(+), 1 deletions(-)

fs/ext4/inode.c +39 -1

index 79930df..50d700f 100644
@@ -1488,6 +1488,44 @@ out:
 
 	return ret;
 }
+/* FIXME!! only support data=writeback mode */
+static int ext4_da_writepage(struct page *page,
+				struct writeback_control *wbc)
+{
+	struct inode *inode = page->mapping->host;
+	handle_t *handle = NULL;
+	int ret = 0;
+	int err;
+
+	if (ext4_journal_current_handle())
+		goto out_fail;
+
+	handle = ext4_journal_start(inode, ext4_writepage_trans_blocks(inode));
+	if (IS_ERR(handle)) {
+		ret = PTR_ERR(handle);
+		goto out_fail;
+	}
+
+	if (test_opt(inode->i_sb, NOBH) && ext4_should_writeback_data(inode))
+		ret = nobh_writepage(page, ext4_get_block, wbc);
+	else
+		ret = block_write_full_page(page, ext4_get_block, wbc);
+
+	if (!ret && inode->i_size > EXT4_I(inode)->i_disksize) {
+		EXT4_I(inode)->i_disksize = inode->i_size;
+		ext4_mark_inode_dirty(handle, inode);
+	}
+
+	err = ext4_journal_stop(handle);
+	if (!ret)
+		ret = err;
+	return ret;
+
+out_fail:
+	redirty_page_for_writepage(wbc, page);
+	unlock_page(page);
+	return ret;
+}
 
 static int ext4_da_writepages(struct address_space *mapping,
 				struct writeback_control *wbc)

@@ -2015,7 +2053,7 @@ static const struct address_space_operations ext4_journalled_aops = {
 static const struct address_space_operations ext4_da_aops = {
 	.readpage	= ext4_readpage,
 	.readpages	= ext4_readpages,
-	.writepage	= ext4_writeback_writepage,
+	.writepage	= ext4_da_writepage,
 	.writepages	= ext4_da_writepages,
 	.sync_page	= block_sync_page,
 	.write_begin	= ext4_da_write_begin,