Btrfs: Add zlib compression support

This is a large change for adding compression on reading and writing,
both for inline and regular extents.  It does some fairly large
surgery to the writeback paths.

Compression is off by default and enabled by mount -o compress.  Even
when the -o compress mount option is not used, it is possible to read
compressed extents off the disk.

If compression for a given set of pages fails to make them smaller, the
file is flagged to avoid future compression attempts later.

* While finding delalloc extents, the pages are locked before being sent down
to the delalloc handler.  This allows the delalloc handler to do complex things
such as cleaning the pages, marking them writeback and starting IO on their
behalf.

* Inline extents are inserted at delalloc time now.  This allows us to compress
the data before inserting the inline extent, and it allows us to insert
an inline extent that spans multiple pages.

* All of the in-memory extent representations (extent_map.c, ordered-data.c etc)
are changed to record both an in-memory size and an on disk size, as well
as a flag for compression.

From a disk format point of view, the extent pointers in the file are changed
to record the on disk size of a given extent and some encoding flags.
Space in the disk format is allocated for compression encoding, as well
as encryption and a generic 'other' field.  Neither the encryption or the
'other' field are currently used.

In order to limit the amount of data read for a single random read in the
file, the size of a compressed extent is limited to 128k.  This is a
software only limit, the disk format supports u64 sized compressed extents.

In order to limit the ram consumed while processing extents, the uncompressed
size of a compressed extent is limited to 256k.  This is a software only limit
and will be subject to tuning later.

Checksumming is still done on compressed extents, and it is done on the
uncompressed version of the data.  This way additional encodings can be
layered on without having to figure out which encoding to checksum.

Compression happens at delalloc time, which is basically singled threaded because
it is usually done by a single pdflush thread.  This makes it tricky to
spread the compression load across all the cpus on the box.  We'll have to
look at parallel pdflush walks of dirty inodes at a later time.

Decompression is hooked into readpages and it does spread across CPUs nicely.

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

1 files changed, 58 insertions, 205 deletions

diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index 69abbe1..0aa1543 100644
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -95,153 +95,6 @@ static void noinline btrfs_drop_pages(struct page **pages, size_t num_pages)
 	}
 }
 
-/* this does all the hard work for inserting an inline extent into
- * the btree.  Any existing inline extent is extended as required to make room,
- * otherwise things are inserted as required into the btree
- */
-static int noinline insert_inline_extent(struct btrfs_trans_handle *trans,
-				struct btrfs_root *root, struct inode *inode,
-				u64 offset, size_t size,
-				struct page **pages, size_t page_offset,
-				int num_pages)
-{
-	struct btrfs_key key;
-	struct btrfs_path *path;
-	struct extent_buffer *leaf;
-	char *kaddr;
-	unsigned long ptr;
-	struct btrfs_file_extent_item *ei;
-	struct page *page;
-	u32 datasize;
-	int err = 0;
-	int ret;
-	int i;
-	ssize_t cur_size;
-
-	path = btrfs_alloc_path();
-	if (!path)
-		return -ENOMEM;
-
-	btrfs_set_trans_block_group(trans, inode);
-
-	key.objectid = inode->i_ino;
-	key.offset = offset;
-	btrfs_set_key_type(&key, BTRFS_EXTENT_DATA_KEY);
-
-	ret = btrfs_search_slot(trans, root, &key, path, 0, 1);
-	if (ret < 0) {
-		err = ret;
-		goto fail;
-	}
-	if (ret == 1) {
-		struct btrfs_key found_key;
-
-		if (path->slots[0] == 0)
-			goto insert;
-
-		path->slots[0]--;
-		leaf = path->nodes[0];
-		btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
-
-		if (found_key.objectid != inode->i_ino)
-			goto insert;
-
-		if (found_key.type != BTRFS_EXTENT_DATA_KEY)
-			goto insert;
-		ei = btrfs_item_ptr(leaf, path->slots[0],
-				    struct btrfs_file_extent_item);
-
-		if (btrfs_file_extent_type(leaf, ei) !=
-		    BTRFS_FILE_EXTENT_INLINE) {
-			goto insert;
-		}
-		btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
-		ret = 0;
-	}
-	if (ret == 0) {
-		u32 found_size;
-		u64 found_end;
-
-		leaf = path->nodes[0];
-		ei = btrfs_item_ptr(leaf, path->slots[0],
-				    struct btrfs_file_extent_item);
-
-		if (btrfs_file_extent_type(leaf, ei) !=
-		    BTRFS_FILE_EXTENT_INLINE) {
-			err = ret;
-			btrfs_print_leaf(root, leaf);
-			printk("found wasn't inline offset %Lu inode %lu\n",
-			       offset, inode->i_ino);
-			goto fail;
-		}
-		found_size = btrfs_file_extent_inline_len(leaf,
-					  btrfs_item_nr(leaf, path->slots[0]));
-		found_end = key.offset + found_size;
-
-		if (found_end < offset + size) {
-			btrfs_release_path(root, path);
-			ret = btrfs_search_slot(trans, root, &key, path,
-						offset + size - found_end, 1);
-			BUG_ON(ret != 0);
-
-			ret = btrfs_extend_item(trans, root, path,
-						offset + size - found_end);
-			if (ret) {
-				err = ret;
-				goto fail;
-			}
-			leaf = path->nodes[0];
-			ei = btrfs_item_ptr(leaf, path->slots[0],
-					    struct btrfs_file_extent_item);
-			inode_add_bytes(inode, offset + size - found_end);
-		}
-		if (found_end < offset) {
-			ptr = btrfs_file_extent_inline_start(ei) + found_size;
-			memset_extent_buffer(leaf, 0, ptr, offset - found_end);
-		}
-	} else {
-insert:
-		btrfs_release_path(root, path);
-		datasize = offset + size - key.offset;
-		inode_add_bytes(inode, datasize);
-		datasize = btrfs_file_extent_calc_inline_size(datasize);
-		ret = btrfs_insert_empty_item(trans, root, path, &key,
-					      datasize);
-		if (ret) {
-			err = ret;
-			printk("got bad ret %d\n", ret);
-			goto fail;
-		}
-		leaf = path->nodes[0];
-		ei = btrfs_item_ptr(leaf, path->slots[0],
-				    struct btrfs_file_extent_item);
-		btrfs_set_file_extent_generation(leaf, ei, trans->transid);
-		btrfs_set_file_extent_type(leaf, ei, BTRFS_FILE_EXTENT_INLINE);
-	}
-	ptr = btrfs_file_extent_inline_start(ei) + offset - key.offset;
-
-	cur_size = size;
-	i = 0;
-	while (size > 0) {
-		page = pages[i];
-		kaddr = kmap_atomic(page, KM_USER0);
-		cur_size = min_t(size_t, PAGE_CACHE_SIZE - page_offset, size);
-		write_extent_buffer(leaf, kaddr + page_offset, ptr, cur_size);
-		kunmap_atomic(kaddr, KM_USER0);
-		page_offset = 0;
-		ptr += cur_size;
-		size -= cur_size;
-		if (i >= num_pages) {
-			printk("i %d num_pages %d\n", i, num_pages);
-		}
-		i++;
-	}
-	btrfs_mark_buffer_dirty(leaf);
-fail:
-	btrfs_free_path(path);
-	return err;
-}
-
 /*
  * after copy_from_user, pages need to be dirtied and we need to make
  * sure holes are created between the current EOF and the start of
@@ -267,8 +120,6 @@ static int noinline dirty_and_release_pages(struct btrfs_trans_handle *trans,
 	u64 start_pos;
 	u64 end_of_last_block;
 	u64 end_pos = pos + write_bytes;
-	u64 inline_size;
-	int did_inline = 0;
 	loff_t isize = i_size_read(inode);
 
 	start_pos = pos & ~((u64)root->sectorsize - 1);
@@ -314,7 +165,8 @@ static int noinline dirty_and_release_pages(struct btrfs_trans_handle *trans,
 			err = btrfs_insert_file_extent(trans, root,
 						       inode->i_ino,
 						       last_pos_in_file,
-						       0, 0, hole_size, 0);
+						       0, 0, hole_size, 0,
+						       hole_size, 0, 0, 0);
 			btrfs_drop_extent_cache(inode, last_pos_in_file,
 					last_pos_in_file + hole_size - 1, 0);
 			mutex_unlock(&BTRFS_I(inode)->extent_mutex);
@@ -324,57 +176,19 @@ static int noinline dirty_and_release_pages(struct btrfs_trans_handle *trans,
 			goto failed;
 	}
 
-	/*
-	 * either allocate an extent for the new bytes or setup the key
-	 * to show we are doing inline data in the extent
+	/* check for reserved extents on each page, we don't want
+	 * to reset the delalloc bit on things that already have
+	 * extents reserved.
 	 */
-	inline_size = end_pos;
-	if (isize >= BTRFS_MAX_INLINE_DATA_SIZE(root) ||
-	    inline_size > root->fs_info->max_inline ||
-	    (inline_size & (root->sectorsize -1)) == 0 ||
-	    inline_size >= BTRFS_MAX_INLINE_DATA_SIZE(root)) {
-		/* check for reserved extents on each page, we don't want
-		 * to reset the delalloc bit on things that already have
-		 * extents reserved.
-		 */
-		btrfs_set_extent_delalloc(inode, start_pos, end_of_last_block);
-		for (i = 0; i < num_pages; i++) {
-			struct page *p = pages[i];
-			SetPageUptodate(p);
-			ClearPageChecked(p);
-			set_page_dirty(p);
-		}
-	} else {
-		u64 aligned_end;
-		/* step one, delete the existing extents in this range */
-		aligned_end = (pos + write_bytes + root->sectorsize - 1) &
-			~((u64)root->sectorsize - 1);
-		mutex_lock(&BTRFS_I(inode)->extent_mutex);
-		err = btrfs_drop_extents(trans, root, inode, start_pos,
-					 aligned_end, aligned_end, &hint_byte);
-		if (err)
-			goto failed;
-		if (isize > inline_size)
-			inline_size = min_t(u64, isize, aligned_end);
-		inline_size -= start_pos;
-		err = insert_inline_extent(trans, root, inode, start_pos,
-					   inline_size, pages, 0, num_pages);
-		btrfs_drop_extent_cache(inode, start_pos, aligned_end - 1, 0);
-		BUG_ON(err);
-		mutex_unlock(&BTRFS_I(inode)->extent_mutex);
-
-		/*
-		 * an ugly way to do all the prop accounting around
-		 * the page bits and mapping tags
-		 */
-		set_page_writeback(pages[0]);
-		end_page_writeback(pages[0]);
-		did_inline = 1;
+	btrfs_set_extent_delalloc(inode, start_pos, end_of_last_block);
+	for (i = 0; i < num_pages; i++) {
+		struct page *p = pages[i];
+		SetPageUptodate(p);
+		ClearPageChecked(p);
+		set_page_dirty(p);
 	}
 	if (end_pos > isize) {
 		i_size_write(inode, end_pos);
-		if (did_inline)
-			BTRFS_I(inode)->disk_i_size = end_pos;
 		btrfs_update_inode(trans, root, inode);
 	}
 failed:
@@ -399,6 +213,7 @@ int btrfs_drop_extent_cache(struct inode *inode, u64 start, u64 end,
 	int ret;
 	int testend = 1;
 	unsigned long flags;
+	int compressed = 0;
 
 	WARN_ON(end < start);
 	if (end == (u64)-1) {
@@ -434,6 +249,7 @@ int btrfs_drop_extent_cache(struct inode *inode, u64 start, u64 end,
 			free_extent_map(em);
 			continue;
 		}
+		compressed = test_bit(EXTENT_FLAG_COMPRESSED, &em->flags);
 		clear_bit(EXTENT_FLAG_PINNED, &em->flags);
 		remove_extent_mapping(em_tree, em);
 
@@ -442,6 +258,12 @@ int btrfs_drop_extent_cache(struct inode *inode, u64 start, u64 end,
 			split->start = em->start;
 			split->len = start - em->start;
 			split->block_start = em->block_start;
+
+			if (compressed)
+				split->block_len = em->block_len;
+			else
+				split->block_len = split->len;
+
 			split->bdev = em->bdev;
 			split->flags = flags;
 			ret = add_extent_mapping(em_tree, split);
@@ -459,7 +281,13 @@ int btrfs_drop_extent_cache(struct inode *inode, u64 start, u64 end,
 			split->bdev = em->bdev;
 			split->flags = flags;
 
-			split->block_start = em->block_start + diff;
+			if (compressed) {
+				split->block_len = em->block_len;
+				split->block_start = em->block_start;
+			} else {
+				split->block_len = split->len;
+				split->block_start = em->block_start + diff;
+			}
 
 			ret = add_extent_mapping(em_tree, split);
 			BUG_ON(ret);
@@ -533,7 +361,7 @@ int btrfs_check_file(struct btrfs_root *root, struct inode *inode)
 			struct btrfs_item *item;
 			item = btrfs_item_nr(leaf, slot);
 			extent_end = found_key.offset +
-			     btrfs_file_extent_inline_len(leaf, item);
+			     btrfs_file_extent_inline_len(leaf, extent);
 			extent_end = (extent_end + root->sectorsize - 1) &
 				~((u64)root->sectorsize -1 );
 		}
@@ -573,6 +401,10 @@ int noinline btrfs_drop_extents(struct btrfs_trans_handle *trans,
 	u64 extent_end = 0;
 	u64 search_start = start;
 	u64 leaf_start;
+	u64 ram_bytes = 0;
+	u8 compression = 0;
+	u8 encryption = 0;
+	u16 other_encoding = 0;
 	u64 root_gen;
 	u64 root_owner;
 	struct extent_buffer *leaf;
@@ -589,6 +421,7 @@ int noinline btrfs_drop_extents(struct btrfs_trans_handle *trans,
 	int recow;
 	int ret;
 
+	inline_limit = 0;
 	btrfs_drop_extent_cache(inode, start, end - 1, 0);
 
 	path = btrfs_alloc_path();
@@ -637,6 +470,12 @@ next_slot:
 			extent = btrfs_item_ptr(leaf, slot,
 						struct btrfs_file_extent_item);
 			found_type = btrfs_file_extent_type(leaf, extent);
+			compression = btrfs_file_extent_compression(leaf,
+								    extent);
+			encryption = btrfs_file_extent_encryption(leaf,
+								  extent);
+			other_encoding = btrfs_file_extent_other_encoding(leaf,
+								  extent);
 			if (found_type == BTRFS_FILE_EXTENT_REG) {
 				extent_end =
 				     btrfs_file_extent_disk_bytenr(leaf,
@@ -646,13 +485,13 @@ next_slot:
 
 				extent_end = key.offset +
 				     btrfs_file_extent_num_bytes(leaf, extent);
+				ram_bytes = btrfs_file_extent_ram_bytes(leaf,
+								extent);
 				found_extent = 1;
 			} else if (found_type == BTRFS_FILE_EXTENT_INLINE) {
-				struct btrfs_item *item;
-				item = btrfs_item_nr(leaf, slot);
 				found_inline = 1;
 				extent_end = key.offset +
-				     btrfs_file_extent_inline_len(leaf, item);
+				     btrfs_file_extent_inline_len(leaf, extent);
 			}
 		} else {
 			extent_end = search_start;
@@ -680,10 +519,9 @@ next_slot:
 			search_start = (extent_end + mask) & ~mask;
 		} else
 			search_start = extent_end;
-		if (end <= extent_end && start >= key.offset && found_inline) {
+
+		if (end <= extent_end && start >= key.offset && found_inline)
 			*hint_byte = EXTENT_MAP_INLINE;
-			goto out;
-		}
 
 		if (found_extent) {
 			read_extent_buffer(leaf, &old, (unsigned long)extent,
@@ -770,12 +608,27 @@ next_slot:
 			write_extent_buffer(leaf, &old,
 					    (unsigned long)extent, sizeof(old));
 
+			btrfs_set_file_extent_compression(leaf, extent,
+							  compression);
+			btrfs_set_file_extent_encryption(leaf, extent,
+							 encryption);
+			btrfs_set_file_extent_other_encoding(leaf, extent,
+							     other_encoding);
 			btrfs_set_file_extent_offset(leaf, extent,
 				    le64_to_cpu(old.offset) + end - key.offset);
 			WARN_ON(le64_to_cpu(old.num_bytes) <
 				(extent_end - end));
 			btrfs_set_file_extent_num_bytes(leaf, extent,
 							extent_end - end);
+
+			/*
+			 * set the ram bytes to the size of the full extent
+			 * before splitting.  This is a worst case flag,
+			 * but its the best we can do because we don't know
+			 * how splitting affects compression
+			 */
+			btrfs_set_file_extent_ram_bytes(leaf, extent,
+							ram_bytes);
 			btrfs_set_file_extent_type(leaf, extent,
 						   BTRFS_FILE_EXTENT_REG);