Btrfs: split up super.c

Signed-off-by: Chris Mason <chris.mason@oracle.com>

fs/btrfs/Makefile

@@ -4,7 +4,7 @@ ifneq ($(KERNELRELEASE),)
 obj-m  := btrfs.o
 btrfs-y := super.o ctree.o extent-tree.o print-tree.o root-tree.o dir-item.o \
 	   hash.o file-item.o inode-item.o inode-map.o disk-io.o \
-	   transaction.o bit-radix.o
+	   transaction.o bit-radix.o inode.o file.o
 
 #btrfs-y := ctree.o disk-io.o radix-tree.o extent-tree.o print-tree.o \
 #	  root-tree.o dir-item.o hash.o file-item.o inode-item.o \
@@ -16,7 +16,7 @@ else
 
 KERNELDIR := /lib/modules/`uname -r`/build
 all::
-	$(MAKE) C=1 -C $(KERNELDIR) M=`pwd` modules
+	$(MAKE) -C $(KERNELDIR) M=`pwd` modules
 clean::
 	rm *.o btrfs.ko
 endif

fs/btrfs/TODO

@@ -1,3 +1,4 @@
+* fix printk warnings
 * cleanup, add more error checking, get rid of BUG_ONs
 * Fix ENOSPC handling
 * Make allocator smarter

fs/btrfs/ctree.h

@@ -1123,5 +1123,28 @@ struct btrfs_csum_item *btrfs_lookup_csum(struct btrfs_trans_handle *trans,
 int btrfs_csum_truncate(struct btrfs_trans_handle *trans,
 			struct btrfs_root *root, struct btrfs_path *path,
 			u64 isize);
-/* super.c */
+/* inode.c */
+void btrfs_delete_inode(struct inode *inode);
+void btrfs_read_locked_inode(struct inode *inode);
+int btrfs_write_inode(struct inode *inode, int wait);
+void btrfs_dirty_inode(struct inode *inode);
+struct inode *btrfs_alloc_inode(struct super_block *sb);
+void btrfs_destroy_inode(struct inode *inode);
+int btrfs_init_cachep(void);
+void btrfs_destroy_cachep(void);
+int btrfs_ioctl(struct inode *inode, struct file *filp, unsigned int cmd,
+		unsigned long arg);
+long btrfs_compat_ioctl(struct file *file, unsigned int cmd,
+			       unsigned long arg);
+struct inode *btrfs_iget_locked(struct super_block *s, u64 objectid,
+				struct btrfs_root *root);
+int btrfs_commit_write(struct file *file, struct page *page,
+		       unsigned from, unsigned to);
+int btrfs_get_block(struct inode *inode, sector_t iblock,
+		    struct buffer_head *result, int create);
+/* file.c */
+extern struct file_operations btrfs_file_operations;
+int btrfs_drop_extents(struct btrfs_trans_handle *trans,
+		       struct btrfs_root *root, struct inode *inode,
+		       u64 start, u64 end, u64 *hint_block);
 #endif

fs/btrfs/disk-io.c

@@ -22,7 +22,7 @@ static int check_tree_block(struct btrfs_root *root, struct buffer_head *buf)
 	if (bh_blocknr(buf) != btrfs_header_blocknr(&node->header)) {
 		printk(KERN_CRIT "bh_blocknr(buf) is %Lu, header is %Lu\n",
 		       bh_blocknr(buf), btrfs_header_blocknr(&node->header));
-		BUG();
+		return 1;
 	}
 	return 0;
 }
@@ -253,7 +253,7 @@ uptodate:
 		set_buffer_checked(bh);
 	}
 	if (check_tree_block(root, bh))
-		BUG();
+		goto fail;
 	return bh;
 fail:
 	brelse(bh);
@@ -398,8 +398,13 @@ struct btrfs_root *open_ctree(struct super_block *sb)
 	struct btrfs_fs_info *fs_info = kmalloc(sizeof(*fs_info),
 						GFP_NOFS);
 	int ret;
+	int err = -EIO;
 	struct btrfs_super_block *disk_super;
 
+	if (!extent_root || !tree_root || !fs_info) {
+		err = -ENOMEM;
+		goto fail;
+	}
 	init_bit_radix(&fs_info->pinned_radix);
 	init_bit_radix(&fs_info->pending_del_radix);
 	init_bit_radix(&fs_info->extent_map_radix);
@@ -431,9 +436,11 @@ struct btrfs_root *open_ctree(struct super_block *sb)
 	mapping_set_gfp_mask(fs_info->btree_inode->i_mapping, GFP_NOFS);
 	fs_info->hash_tfm = crypto_alloc_hash("crc32c", 0, CRYPTO_ALG_ASYNC);
 	spin_lock_init(&fs_info->hash_lock);
+
 	if (!fs_info->hash_tfm || IS_ERR(fs_info->hash_tfm)) {
-		printk("failed to allocate digest hash\n");
-		return NULL;
+		printk("btrfs: failed hash setup, modprobe cryptomgr?\n");
+		err = -ENOMEM;
+		goto fail_iput;
 	}
 	mutex_init(&fs_info->trans_mutex);
 	mutex_init(&fs_info->fs_mutex);
@@ -446,30 +453,53 @@ struct btrfs_root *open_ctree(struct super_block *sb)
 					     sb->s_blocksize);
 
 	if (!fs_info->sb_buffer)
-		return NULL;
+		goto fail_iput;
 	disk_super = (struct btrfs_super_block *)fs_info->sb_buffer->b_data;
+
 	if (!btrfs_super_root(disk_super))
-		return NULL;
+		goto fail_sb_buffer;
 
 	i_size_write(fs_info->btree_inode,
 		     btrfs_super_total_blocks(disk_super) <<
 		     fs_info->btree_inode->i_blkbits);
 
 	fs_info->disk_super = disk_super;
+
+	if (strncmp((char *)(&disk_super->magic), BTRFS_MAGIC,
+		    sizeof(disk_super->magic))) {
+		printk("btrfs: valid FS not found on %s\n", sb->s_id);
+		goto fail_sb_buffer;
+	}
 	tree_root->node = read_tree_block(tree_root,
 					  btrfs_super_root(disk_super));
-	BUG_ON(!tree_root->node);
+	if (!tree_root->node)
+		goto fail_sb_buffer;
 
 	mutex_lock(&fs_info->fs_mutex);
 	ret = find_and_setup_root(sb->s_blocksize, tree_root, fs_info,
 				  BTRFS_EXTENT_TREE_OBJECTID, extent_root);
-	BUG_ON(ret);
+	if (ret) {
+		mutex_unlock(&fs_info->fs_mutex);
+		goto fail_tree_root;
+	}
 
 	btrfs_read_block_groups(extent_root);
 
 	fs_info->generation = btrfs_super_generation(disk_super) + 1;
 	mutex_unlock(&fs_info->fs_mutex);
 	return tree_root;
+
+fail_tree_root:
+	btrfs_block_release(tree_root, tree_root->node);
+fail_sb_buffer:
+	btrfs_block_release(tree_root, fs_info->sb_buffer);
+fail_iput:
+	iput(fs_info->btree_inode);
+fail:
+	kfree(extent_root);
+	kfree(tree_root);
+	kfree(fs_info);
+	return ERR_PTR(err);
 }
 
 int write_ctree_super(struct btrfs_trans_handle *trans, struct btrfs_root

fs/btrfs/file.c

@@ -0,0 +1,783 @@
+#include <linux/module.h>
+#include <linux/buffer_head.h>
+#include <linux/fs.h>
+#include <linux/pagemap.h>
+#include <linux/highmem.h>
+#include <linux/time.h>
+#include <linux/init.h>
+#include <linux/string.h>
+#include <linux/smp_lock.h>
+#include <linux/backing-dev.h>
+#include <linux/mpage.h>
+#include <linux/swap.h>
+#include <linux/writeback.h>
+#include <linux/statfs.h>
+#include <linux/compat.h>
+#include "ctree.h"
+#include "disk-io.h"
+#include "transaction.h"
+#include "btrfs_inode.h"
+#include "ioctl.h"
+#include "print-tree.h"
+
+
+static int btrfs_copy_from_user(loff_t pos, int num_pages, int write_bytes,
+				struct page **prepared_pages,
+				const char __user * buf)
+{
+	long page_fault = 0;
+	int i;
+	int offset = pos & (PAGE_CACHE_SIZE - 1);
+
+	for (i = 0; i < num_pages && write_bytes > 0; i++, offset = 0) {
+		size_t count = min_t(size_t,
+				     PAGE_CACHE_SIZE - offset, write_bytes);
+		struct page *page = prepared_pages[i];
+		fault_in_pages_readable(buf, count);
+
+		/* Copy data from userspace to the current page */
+		kmap(page);
+		page_fault = __copy_from_user(page_address(page) + offset,
+					      buf, count);
+		/* Flush processor's dcache for this page */
+		flush_dcache_page(page);
+		kunmap(page);
+		buf += count;
+		write_bytes -= count;
+
+		if (page_fault)
+			break;
+	}
+	return page_fault ? -EFAULT : 0;
+}
+
+static void btrfs_drop_pages(struct page **pages, size_t num_pages)
+{
+	size_t i;
+	for (i = 0; i < num_pages; i++) {
+		if (!pages[i])
+			break;
+		unlock_page(pages[i]);
+		mark_page_accessed(pages[i]);
+		page_cache_release(pages[i]);
+	}
+}
+
+static int dirty_and_release_pages(struct btrfs_trans_handle *trans,
+				   struct btrfs_root *root,
+				   struct file *file,
+				   struct page **pages,
+				   size_t num_pages,
+				   loff_t pos,
+				   size_t write_bytes)
+{
+	int i;
+	int offset;
+	int err = 0;
+	int ret;
+	int this_write;
+	struct inode *inode = file->f_path.dentry->d_inode;
+	struct buffer_head *bh;
+	struct btrfs_file_extent_item *ei;
+
+	for (i = 0; i < num_pages; i++) {
+		offset = pos & (PAGE_CACHE_SIZE -1);
+		this_write = min(PAGE_CACHE_SIZE - offset, write_bytes);
+		/* FIXME, one block at a time */
+
+		mutex_lock(&root->fs_info->fs_mutex);
+		trans = btrfs_start_transaction(root, 1);
+		btrfs_set_trans_block_group(trans, inode);
+
+		bh = page_buffers(pages[i]);
+
+		if (buffer_mapped(bh) && bh->b_blocknr == 0) {
+			struct btrfs_key key;
+			struct btrfs_path *path;
+			char *ptr;
+			u32 datasize;
+
+			/* create an inline extent, and copy the data in */
+			path = btrfs_alloc_path();
+			BUG_ON(!path);
+			key.objectid = inode->i_ino;
+			key.offset = pages[i]->index << PAGE_CACHE_SHIFT;
+			key.flags = 0;
+			btrfs_set_key_type(&key, BTRFS_EXTENT_DATA_KEY);
+			BUG_ON(write_bytes >= PAGE_CACHE_SIZE);
+			datasize = offset +
+				btrfs_file_extent_calc_inline_size(write_bytes);
+
+			ret = btrfs_insert_empty_item(trans, root, path, &key,
+						      datasize);
+			BUG_ON(ret);
+			ei = btrfs_item_ptr(btrfs_buffer_leaf(path->nodes[0]),
+			       path->slots[0], struct btrfs_file_extent_item);
+			btrfs_set_file_extent_generation(ei, trans->transid);
+			btrfs_set_file_extent_type(ei,
+						   BTRFS_FILE_EXTENT_INLINE);
+			ptr = btrfs_file_extent_inline_start(ei);
+			btrfs_memcpy(root, path->nodes[0]->b_data,
+				     ptr, bh->b_data, offset + write_bytes);
+			mark_buffer_dirty(path->nodes[0]);
+			btrfs_free_path(path);
+		} else if (buffer_mapped(bh)) {
+			/* csum the file data */
+			btrfs_csum_file_block(trans, root, inode->i_ino,
+				      pages[i]->index << PAGE_CACHE_SHIFT,
+				      kmap(pages[i]), PAGE_CACHE_SIZE);
+			kunmap(pages[i]);
+		}
+		SetPageChecked(pages[i]);
+		ret = btrfs_end_transaction(trans, root);
+		BUG_ON(ret);
+		mutex_unlock(&root->fs_info->fs_mutex);
+
+		ret = btrfs_commit_write(file, pages[i], offset,
+					 offset + this_write);
+		pos += this_write;
+		if (ret) {
+			err = ret;
+			goto failed;
+		}
+		WARN_ON(this_write > write_bytes);
+		write_bytes -= this_write;
+	}
+failed:
+	return err;
+}
+
+/*
+ * this is very complex, but the basic idea is to drop all extents
+ * in the range start - end.  hint_block is filled in with a block number
+ * that would be a good hint to the block allocator for this file.
+ *
+ * If an extent intersects the range but is not entirely inside the range
+ * it is either truncated or split.  Anything entirely inside the range
+ * is deleted from the tree.
+ */
+int btrfs_drop_extents(struct btrfs_trans_handle *trans,
+		       struct btrfs_root *root, struct inode *inode,
+		       u64 start, u64 end, u64 *hint_block)
+{
+	int ret;
+	struct btrfs_key key;
+	struct btrfs_leaf *leaf;
+	int slot;
+	struct btrfs_file_extent_item *extent;
+	u64 extent_end = 0;
+	int keep;
+	struct btrfs_file_extent_item old;
+	struct btrfs_path *path;
+	u64 search_start = start;
+	int bookend;
+	int found_type;
+	int found_extent;
+	int found_inline;
+
+	path = btrfs_alloc_path();
+	if (!path)
+		return -ENOMEM;
+	while(1) {
+		btrfs_release_path(root, path);
+		ret = btrfs_lookup_file_extent(trans, root, path, inode->i_ino,
+					       search_start, -1);
+		if (ret < 0)
+			goto out;
+		if (ret > 0) {
+			if (path->slots[0] == 0) {
+				ret = 0;
+				goto out;
+			}
+			path->slots[0]--;
+		}
+		keep = 0;
+		bookend = 0;
+		found_extent = 0;
+		found_inline = 0;
+		extent = NULL;
+		leaf = btrfs_buffer_leaf(path->nodes[0]);
+		slot = path->slots[0];
+		btrfs_disk_key_to_cpu(&key, &leaf->items[slot].key);
+		if (key.offset >= end || key.objectid != inode->i_ino) {
+			ret = 0;
+			goto out;
+		}
+		if (btrfs_key_type(&key) != BTRFS_EXTENT_DATA_KEY) {
+			ret = 0;
+			goto out;
+		}
+		extent = btrfs_item_ptr(leaf, slot,
+					struct btrfs_file_extent_item);
+		found_type = btrfs_file_extent_type(extent);
+		if (found_type == BTRFS_FILE_EXTENT_REG) {
+			extent_end = key.offset +
+				(btrfs_file_extent_num_blocks(extent) <<
+				 inode->i_blkbits);
+			found_extent = 1;
+		} else if (found_type == BTRFS_FILE_EXTENT_INLINE) {
+			found_inline = 1;
+			extent_end = key.offset +
+			     btrfs_file_extent_inline_len(leaf->items + slot);
+		}
+
+		/* we found nothing we can drop */
+		if (!found_extent && !found_inline) {
+			ret = 0;
+			goto out;
+		}
+
+		/* we found nothing inside the range */
+		if (search_start >= extent_end) {
+			ret = 0;
+			goto out;
+		}
+
+		/* FIXME, there's only one inline extent allowed right now */
+		if (found_inline) {
+			u64 mask = root->blocksize - 1;
+			search_start = (extent_end + mask) & ~mask;
+		} else
+			search_start = extent_end;
+
+		if (end < extent_end && end >= key.offset) {
+			if (found_extent) {
+				u64 disk_blocknr =
+					btrfs_file_extent_disk_blocknr(extent);
+				u64 disk_num_blocks =
+				      btrfs_file_extent_disk_num_blocks(extent);
+				memcpy(&old, extent, sizeof(old));
+				if (disk_blocknr != 0) {
+					ret = btrfs_inc_extent_ref(trans, root,
+					         disk_blocknr, disk_num_blocks);
+					BUG_ON(ret);
+				}
+			}
+			WARN_ON(found_inline);
+			bookend = 1;
+		}
+
+		/* truncate existing extent */
+		if (start > key.offset) {
+			u64 new_num;
+			u64 old_num;
+			keep = 1;
+			WARN_ON(start & (root->blocksize - 1));
+			if (found_extent) {
+				new_num = (start - key.offset) >>
+					inode->i_blkbits;
+				old_num = btrfs_file_extent_num_blocks(extent);
+				*hint_block =
+					btrfs_file_extent_disk_blocknr(extent);
+				if (btrfs_file_extent_disk_blocknr(extent)) {
+					inode->i_blocks -=
+						(old_num - new_num) << 3;
+				}
+				btrfs_set_file_extent_num_blocks(extent,
+								 new_num);
+				mark_buffer_dirty(path->nodes[0]);
+			} else {
+				WARN_ON(1);
+			}
+		}
+		/* delete the entire extent */
+		if (!keep) {
+			u64 disk_blocknr = 0;
+			u64 disk_num_blocks = 0;
+			u64 extent_num_blocks = 0;
+			if (found_extent) {
+				disk_blocknr =
+				      btrfs_file_extent_disk_blocknr(extent);
+				disk_num_blocks =
+				      btrfs_file_extent_disk_num_blocks(extent);
+				extent_num_blocks =
+				      btrfs_file_extent_num_blocks(extent);
+				*hint_block =
+					btrfs_file_extent_disk_blocknr(extent);
+			}
+			ret = btrfs_del_item(trans, root, path);
+			BUG_ON(ret);
+			btrfs_release_path(root, path);
+			extent = NULL;
+			if (found_extent && disk_blocknr != 0) {
+				inode->i_blocks -= extent_num_blocks << 3;
+				ret = btrfs_free_extent(trans, root,
+							disk_blocknr,
+							disk_num_blocks, 0);
+			}
+
+			BUG_ON(ret);
+			if (!bookend && search_start >= end) {
+				ret = 0;
+				goto out;
+			}
+			if (!bookend)
+				continue;
+		}
+		/* create bookend, splitting the extent in two */
+		if (bookend && found_extent) {
+			struct btrfs_key ins;
+			ins.objectid = inode->i_ino;
+			ins.offset = end;
+			ins.flags = 0;
+			btrfs_set_key_type(&ins, BTRFS_EXTENT_DATA_KEY);
+
+			btrfs_release_path(root, path);
+			ret = btrfs_insert_empty_item(trans, root, path, &ins,
+						      sizeof(*extent));
+			BUG_ON(ret);
+			extent = btrfs_item_ptr(
+				    btrfs_buffer_leaf(path->nodes[0]),
+				    path->slots[0],
+				    struct btrfs_file_extent_item);
+			btrfs_set_file_extent_disk_blocknr(extent,
+				    btrfs_file_extent_disk_blocknr(&old));
+			btrfs_set_file_extent_disk_num_blocks(extent,
+				    btrfs_file_extent_disk_num_blocks(&old));
+
+			btrfs_set_file_extent_offset(extent,
+				    btrfs_file_extent_offset(&old) +
+				    ((end - key.offset) >> inode->i_blkbits));
+			WARN_ON(btrfs_file_extent_num_blocks(&old) <
+				(extent_end - end) >> inode->i_blkbits);
+			btrfs_set_file_extent_num_blocks(extent,
+				    (extent_end - end) >> inode->i_blkbits);
+
+			btrfs_set_file_extent_type(extent,
+						   BTRFS_FILE_EXTENT_REG);
+			btrfs_set_file_extent_generation(extent,
+				    btrfs_file_extent_generation(&old));
+			btrfs_mark_buffer_dirty(path->nodes[0]);
+			if (btrfs_file_extent_disk_blocknr(&old) != 0) {
+				inode->i_blocks +=
+				      btrfs_file_extent_num_blocks(extent) << 3;
+			}
+			ret = 0;
+			goto out;
+		}
+	}
+out:
+	btrfs_free_path(path);
+	return ret;
+}
+
+/*
+ * this gets pages into the page cache and locks them down
+ */
+static int prepare_pages(struct btrfs_root *root,
+			 struct file *file,
+			 struct page **pages,
+			 size_t num_pages,
+			 loff_t pos,
+			 unsigned long first_index,
+			 unsigned long last_index,
+			 size_t write_bytes,
+			 u64 alloc_extent_start)
+{
+	int i;
+	unsigned long index = pos >> PAGE_CACHE_SHIFT;
+	struct inode *inode = file->f_path.dentry->d_inode;
+	int offset;
+	int err = 0;
+	int this_write;
+	struct buffer_head *bh;
+	struct buffer_head *head;
+	loff_t isize = i_size_read(inode);
+
+	memset(pages, 0, num_pages * sizeof(struct page *));
+
+	for (i = 0; i < num_pages; i++) {
+		pages[i] = grab_cache_page(inode->i_mapping, index + i);
+		if (!pages[i]) {
+			err = -ENOMEM;
+			goto failed_release;
+		}
+		cancel_dirty_page(pages[i], PAGE_CACHE_SIZE);
+		wait_on_page_writeback(pages[i]);
+		offset = pos & (PAGE_CACHE_SIZE -1);
+		this_write = min(PAGE_CACHE_SIZE - offset, write_bytes);
+		if (!page_has_buffers(pages[i])) {
+			create_empty_buffers(pages[i],
+					     root->fs_info->sb->s_blocksize,
+					     (1 << BH_Uptodate));
+		}
+		head = page_buffers(pages[i]);
+		bh = head;
+		do {
+			err = btrfs_map_bh_to_logical(root, bh,
+						      alloc_extent_start);
+			BUG_ON(err);
+			if (err)
+				goto failed_truncate;
+			bh = bh->b_this_page;
+			if (alloc_extent_start)
+				alloc_extent_start++;
+		} while (bh != head);
+		pos += this_write;
+		WARN_ON(this_write > write_bytes);
+		write_bytes -= this_write;
+	}
+	return 0;
+
+failed_release:
+	btrfs_drop_pages(pages, num_pages);
+	return err;
+
+failed_truncate:
+	btrfs_drop_pages(pages, num_pages);
+	if (pos > isize)
+		vmtruncate(inode, isize);
+	return err;
+}
+
+static ssize_t btrfs_file_write(struct file *file, const char __user *buf,
+				size_t count, loff_t *ppos)
+{
+	loff_t pos;
+	size_t num_written = 0;
+	int err = 0;
+	int ret = 0;
+	struct inode *inode = file->f_path.dentry->d_inode;
+	struct btrfs_root *root = BTRFS_I(inode)->root;
+	struct page *pages[8];
+	struct page *pinned[2];
+	unsigned long first_index;
+	unsigned long last_index;
+	u64 start_pos;
+	u64 num_blocks;
+	u64 alloc_extent_start;
+	u64 hint_block;
+	struct btrfs_trans_handle *trans;
+	struct btrfs_key ins;
+	pinned[0] = NULL;
+	pinned[1] = NULL;
+	if (file->f_flags & O_DIRECT)
+		return -EINVAL;
+	pos = *ppos;
+	vfs_check_frozen(inode->i_sb, SB_FREEZE_WRITE);
+	current->backing_dev_info = inode->i_mapping->backing_dev_info;
+	err = generic_write_checks(file, &pos, &count, S_ISBLK(inode->i_mode));
+	if (err)
+		goto out;
+	if (count == 0)
+		goto out;
+	err = remove_suid(file->f_path.dentry);
+	if (err)
+		goto out;
+	file_update_time(file);
+
+	start_pos = pos & ~((u64)PAGE_CACHE_SIZE - 1);
+	num_blocks = (count + pos - start_pos + root->blocksize - 1) >>
+			inode->i_blkbits;
+
+	mutex_lock(&inode->i_mutex);
+	first_index = pos >> PAGE_CACHE_SHIFT;
+	last_index = (pos + count) >> PAGE_CACHE_SHIFT;
+
+	/*
+	 * there are lots of better ways to do this, but this code
+	 * makes sure the first and last page in the file range are
+	 * up to date and ready for cow
+	 */
+	if ((pos & (PAGE_CACHE_SIZE - 1))) {
+		pinned[0] = grab_cache_page(inode->i_mapping, first_index);
+		if (!PageUptodate(pinned[0])) {
+			ret = mpage_readpage(pinned[0], btrfs_get_block);
+			BUG_ON(ret);
+			wait_on_page_locked(pinned[0]);
+		} else {
+			unlock_page(pinned[0]);
+		}
+	}
+	if ((pos + count) & (PAGE_CACHE_SIZE - 1)) {
+		pinned[1] = grab_cache_page(inode->i_mapping, last_index);
+		if (!PageUptodate(pinned[1])) {
+			ret = mpage_readpage(pinned[1], btrfs_get_block);
+			BUG_ON(ret);
+			wait_on_page_locked(pinned[1]);
+		} else {
+			unlock_page(pinned[1]);
+		}
+	}
+
+	mutex_lock(&root->fs_info->fs_mutex);
+	trans = btrfs_start_transaction(root, 1);
+	if (!trans) {
+		err = -ENOMEM;
+		mutex_unlock(&root->fs_info->fs_mutex);
+		goto out_unlock;
+	}
+	btrfs_set_trans_block_group(trans, inode);
+	/* FIXME blocksize != 4096 */
+	inode->i_blocks += num_blocks << 3;
+	hint_block = 0;
+
+	/* FIXME...EIEIO, ENOSPC and more */
+
+	/* step one, delete the existing extents in this range */
+	if (start_pos < inode->i_size) {
+		/* FIXME blocksize != pagesize */
+		ret = btrfs_drop_extents(trans, root, inode,
+					 start_pos,
+					 (pos + count + root->blocksize -1) &
+					 ~((u64)root->blocksize - 1),
+					 &hint_block);
+		BUG_ON(ret);
+	}
+
+	/* insert any holes we need to create */
+	if (inode->i_size < start_pos) {
+		u64 last_pos_in_file;
+		u64 hole_size;
+		u64 mask = root->blocksize - 1;
+		last_pos_in_file = (inode->i_size + mask) & ~mask;
+		hole_size = (start_pos - last_pos_in_file + mask) & ~mask;
+		hole_size >>= inode->i_blkbits;
+		if (last_pos_in_file < start_pos) {
+			ret = btrfs_insert_file_extent(trans, root,
+						       inode->i_ino,
+						       last_pos_in_file,
+						       0, 0, hole_size);
+		}
+		BUG_ON(ret);
+	}
+
+	/*
+	 * either allocate an extent for the new bytes or setup the key
+	 * to show we are doing inline data in the extent
+	 */
+	if (inode->i_size >= PAGE_CACHE_SIZE || pos + count < inode->i_size ||
+	    pos + count - start_pos > BTRFS_MAX_INLINE_DATA_SIZE(root)) {
+		ret = btrfs_alloc_extent(trans, root, inode->i_ino,
+					 num_blocks, hint_block, (u64)-1,
+					 &ins, 1);
+		BUG_ON(ret);
+		ret = btrfs_insert_file_extent(trans, root, inode->i_ino,
+				       start_pos, ins.objectid, ins.offset,
+				       ins.offset);
+		BUG_ON(ret);
+	} else {
+		ins.offset = 0;
+		ins.objectid = 0;
+	}
+	BUG_ON(ret);
+	alloc_extent_start = ins.objectid;
+	ret = btrfs_end_transaction(trans, root);
+	mutex_unlock(&root->fs_info->fs_mutex);
+
+	while(count > 0) {
+		size_t offset = pos & (PAGE_CACHE_SIZE - 1);
+		size_t write_bytes = min(count, PAGE_CACHE_SIZE - offset);
+		size_t num_pages = (write_bytes + PAGE_CACHE_SIZE - 1) >>
+					PAGE_CACHE_SHIFT;
+
+		memset(pages, 0, sizeof(pages));
+		ret = prepare_pages(root, file, pages, num_pages,
+				    pos, first_index, last_index,
+				    write_bytes, alloc_extent_start);
+		BUG_ON(ret);
+
+		/* FIXME blocks != pagesize */
+		if (alloc_extent_start)
+			alloc_extent_start += num_pages;
+		ret = btrfs_copy_from_user(pos, num_pages,
+					   write_bytes, pages, buf);
+		BUG_ON(ret);
+
+		ret = dirty_and_release_pages(NULL, root, file, pages,
+					      num_pages, pos, write_bytes);
+		BUG_ON(ret);
+		btrfs_drop_pages(pages, num_pages);
+
+		buf += write_bytes;
+		count -= write_bytes;
+		pos += write_bytes;
+		num_written += write_bytes;
+
+		balance_dirty_pages_ratelimited(inode->i_mapping);
+		btrfs_btree_balance_dirty(root);
+		cond_resched();
+	}
+out_unlock:
+	mutex_unlock(&inode->i_mutex);
+out:
+	if (pinned[0])
+		page_cache_release(pinned[0]);
+	if (pinned[1])
+		page_cache_release(pinned[1]);
+	*ppos = pos;
+	current->backing_dev_info = NULL;
+	mark_inode_dirty(inode);
+	return num_written ? num_written : err;
+}
+
+/*
+ * FIXME, do this by stuffing the csum we want in the info hanging off
+ * page->private.  For now, verify file csums on read
+ */
+static int btrfs_read_actor(read_descriptor_t *desc, struct page *page,
+			unsigned long offset, unsigned long size)
+{
+	char *kaddr;
+	unsigned long left, count = desc->count;
+	struct inode *inode = page->mapping->host;
+
+	if (size > count)
+		size = count;
+
+	if (!PageChecked(page)) {
+		/* FIXME, do it per block */
+		struct btrfs_root *root = BTRFS_I(inode)->root;
+		int ret;
+		struct buffer_head *bh;
+
+		if (page_has_buffers(page)) {
+			bh = page_buffers(page);
+			if (!buffer_mapped(bh)) {
+				SetPageChecked(page);
+				goto checked;
+			}
+		}
+
+		ret = btrfs_csum_verify_file_block(root,
+				  page->mapping->host->i_ino,
+				  page->index << PAGE_CACHE_SHIFT,
+				  kmap(page), PAGE_CACHE_SIZE);
+		if (ret) {
+			if (ret != -ENOENT) {
+				printk("failed to verify ino %lu page %lu ret %d\n",
+				       page->mapping->host->i_ino,
+				       page->index, ret);
+				memset(page_address(page), 1, PAGE_CACHE_SIZE);
+				flush_dcache_page(page);
+			}
+		}
+		SetPageChecked(page);
+		kunmap(page);
+	}
+checked:
+	/*
+	 * Faults on the destination of a read are common, so do it before
+	 * taking the kmap.
+	 */
+	if (!fault_in_pages_writeable(desc->arg.buf, size)) {
+		kaddr = kmap_atomic(page, KM_USER0);
+		left = __copy_to_user_inatomic(desc->arg.buf,
+						kaddr + offset, size);
+		kunmap_atomic(kaddr, KM_USER0);
+		if (left == 0)
+			goto success;
+	}
+
+	/* Do it the slow way */
+	kaddr = kmap(page);
+	left = __copy_to_user(desc->arg.buf, kaddr + offset, size);
+	kunmap(page);
+
+	if (left) {
+		size -= left;
+		desc->error = -EFAULT;
+	}
+success:
+	desc->count = count - size;
+	desc->written += size;
+	desc->arg.buf += size;
+	return size;
+}
+
+/**
+ * btrfs_file_aio_read - filesystem read routine, with a mod to csum verify
+ * @iocb:	kernel I/O control block
+ * @iov:	io vector request
+ * @nr_segs:	number of segments in the iovec
+ * @pos:	current file position
+ */
+static ssize_t btrfs_file_aio_read(struct kiocb *iocb, const struct iovec *iov,
+				   unsigned long nr_segs, loff_t pos)
+{
+	struct file *filp = iocb->ki_filp;
+	ssize_t retval;
+	unsigned long seg;
+	size_t count;
+	loff_t *ppos = &iocb->ki_pos;
+
+	count = 0;
+	for (seg = 0; seg < nr_segs; seg++) {
+		const struct iovec *iv = &iov[seg];
+
+		/*
+		 * If any segment has a negative length, or the cumulative
+		 * length ever wraps negative then return -EINVAL.
+		 */
+		count += iv->iov_len;
+		if (unlikely((ssize_t)(count|iv->iov_len) < 0))
+			return -EINVAL;
+		if (access_ok(VERIFY_WRITE, iv->iov_base, iv->iov_len))
+			continue;
+		if (seg == 0)
+			return -EFAULT;
+		nr_segs = seg;
+		count -= iv->iov_len;	/* This segment is no good */
+		break;
+	}
+	retval = 0;
+	if (count) {
+		for (seg = 0; seg < nr_segs; seg++) {
+			read_descriptor_t desc;
+
+			desc.written = 0;
+			desc.arg.buf = iov[seg].iov_base;
+			desc.count = iov[seg].iov_len;
+			if (desc.count == 0)
+				continue;
+			desc.error = 0;
+			do_generic_file_read(filp, ppos, &desc,
+					     btrfs_read_actor);
+			retval += desc.written;
+			if (desc.error) {
+				retval = retval ?: desc.error;
+				break;
+			}
+		}
+	}
+	return retval;
+}
+
+static int btrfs_sync_file(struct file *file,
+			   struct dentry *dentry, int datasync)
+{
+	struct inode *inode = dentry->d_inode;
+	struct btrfs_root *root = BTRFS_I(inode)->root;
+	int ret;
+	struct btrfs_trans_handle *trans;
+
+	/*
+	 * FIXME, use inode generation number to check if we can skip the
+	 * commit
+	 */
+	mutex_lock(&root->fs_info->fs_mutex);
+	trans = btrfs_start_transaction(root, 1);
+	if (!trans) {
+		ret = -ENOMEM;
+		goto out;
+	}
+	ret = btrfs_commit_transaction(trans, root);
+	mutex_unlock(&root->fs_info->fs_mutex);
+out:
+	return ret > 0 ? EIO : ret;
+}
+
+struct file_operations btrfs_file_operations = {
+	.llseek		= generic_file_llseek,
+	.read		= do_sync_read,
+	.aio_read       = btrfs_file_aio_read,
+	.write		= btrfs_file_write,
+	.mmap		= generic_file_mmap,
+	.open		= generic_file_open,
+	.ioctl		= btrfs_ioctl,
+	.fsync		= btrfs_sync_file,
+#ifdef CONFIG_COMPAT
+	.compat_ioctl	= btrfs_compat_ioctl,
+#endif
+};
+