btrfs: embed a btrfs_bio into struct compressed_bio

Embed a btrfs_bio into struct compressed_bio.  This avoids potential
(so far theoretical) deadlocks due to nesting of btrfs_bioset allocations
for the original read bio and the compressed bio, and avoids an extra
memory allocation in the I/O path.
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/compression.h

@@ -6,8 +6,8 @@
 #ifndef BTRFS_COMPRESSION_H
 #define BTRFS_COMPRESSION_H
 
-#include <linux/blk_types.h>
 #include <linux/sizes.h>
+#include "bio.h"
 
 struct btrfs_inode;
 
@@ -23,6 +23,7 @@ struct btrfs_inode;
 
 /* Maximum length of compressed data stored on disk */
 #define BTRFS_MAX_COMPRESSED		(SZ_128K)
+#define BTRFS_MAX_COMPRESSED_PAGES	(BTRFS_MAX_COMPRESSED / PAGE_SIZE)
 static_assert((BTRFS_MAX_COMPRESSED % PAGE_SIZE) == 0);
 
 /* Maximum size of data before compression */
@@ -37,9 +38,6 @@ struct compressed_bio {
 	/* the pages with the compressed data on them */
 	struct page **compressed_pages;
 
-	/* inode that owns this data */
-	struct inode *inode;
-
 	/* starting offset in the inode for our pages */
 	u64 start;
 
@@ -55,14 +53,14 @@ struct compressed_bio {
 	/* Whether this is a write for writeback. */
 	bool writeback;
 
-	/* IO errors */
-	blk_status_t status;
-
 	union {
 		/* For reads, this is the bio we are copying the data into */
 		struct bio *orig_bio;
 		struct work_struct write_end_work;
 	};
+
+	/* Must be last. */
+	struct btrfs_bio bbio;
 };
 
 static inline unsigned int btrfs_compress_type(unsigned int type_level)
@@ -88,7 +86,7 @@ int btrfs_decompress(int type, const u8 *data_in, struct page *dest_page,
 int btrfs_decompress_buf2page(const char *buf, u32 buf_len,
 			      struct compressed_bio *cb, u32 decompressed);
 
-blk_status_t btrfs_submit_compressed_write(struct btrfs_inode *inode, u64 start,
+void btrfs_submit_compressed_write(struct btrfs_inode *inode, u64 start,
 				  unsigned int len, u64 disk_start,
 				  unsigned int compressed_len,
 				  struct page **compressed_pages,
@@ -96,8 +94,7 @@ blk_status_t btrfs_submit_compressed_write(struct btrfs_inode *inode, u64 start,
 				  blk_opf_t write_flags,
 				  struct cgroup_subsys_state *blkcg_css,
 				  bool writeback);
-void btrfs_submit_compressed_read(struct inode *inode, struct bio *bio,
-				  int mirror_num);
+void btrfs_submit_compressed_read(struct bio *bio, int mirror_num);
 
 unsigned int btrfs_compress_str2level(unsigned int type, const char *str);
 

fs/btrfs/extent_io.c

@@ -156,7 +156,7 @@ static void submit_one_bio(struct btrfs_bio_ctrl *bio_ctrl)
 
 	if (btrfs_op(bio) == BTRFS_MAP_READ &&
 	    bio_ctrl->compress_type != BTRFS_COMPRESS_NONE)
-		btrfs_submit_compressed_read(inode, bio, mirror_num);
+		btrfs_submit_compressed_read(bio, mirror_num);
 	else
 		btrfs_submit_bio(bio, mirror_num);
 

fs/btrfs/inode.c

@@ -669,8 +669,7 @@ static noinline int compress_file_range(struct async_chunk *async_chunk)
 again:
 	will_compress = 0;
 	nr_pages = (end >> PAGE_SHIFT) - (start >> PAGE_SHIFT) + 1;
-	nr_pages = min_t(unsigned long, nr_pages,
-			BTRFS_MAX_COMPRESSED / PAGE_SIZE);
+	nr_pages = min_t(unsigned long, nr_pages, BTRFS_MAX_COMPRESSED_PAGES);
 
 	/*
 	 * we don't want to send crud past the end of i_size through
@@ -1054,23 +1053,14 @@ static int submit_one_async_extent(struct btrfs_inode *inode,
 	extent_clear_unlock_delalloc(inode, start, end,
 			NULL, EXTENT_LOCKED | EXTENT_DELALLOC,
 			PAGE_UNLOCK | PAGE_START_WRITEBACK);
-	if (btrfs_submit_compressed_write(inode, start,	/* file_offset */
+	btrfs_submit_compressed_write(inode, start,	/* file_offset */
 			    async_extent->ram_size,	/* num_bytes */
 			    ins.objectid,		/* disk_bytenr */
 			    ins.offset,			/* compressed_len */
 			    async_extent->pages,	/* compressed_pages */
 			    async_extent->nr_pages,
 			    async_chunk->write_flags,
-			    async_chunk->blkcg_css, true)) {
-		const u64 start = async_extent->start;
-		const u64 end = start + async_extent->ram_size - 1;
-
-		btrfs_writepage_endio_finish_ordered(inode, NULL, start, end, 0);
-
-		extent_clear_unlock_delalloc(inode, start, end, NULL, 0,
-					     PAGE_END_WRITEBACK | PAGE_SET_ERROR);
-		free_async_extent_pages(async_extent);
-	}
+			    async_chunk->blkcg_css, true);
 	*alloc_hint = ins.objectid + ins.offset;
 	kfree(async_extent);
 	return ret;
@@ -10395,13 +10385,9 @@ ssize_t btrfs_do_encoded_write(struct kiocb *iocb, struct iov_iter *from,
 
 	btrfs_delalloc_release_extents(inode, num_bytes);
 
-	if (btrfs_submit_compressed_write(inode, start, num_bytes, ins.objectid,
+	btrfs_submit_compressed_write(inode, start, num_bytes, ins.objectid,
 					  ins.offset, pages, nr_pages, 0, NULL,
-					  false)) {
-		btrfs_writepage_endio_finish_ordered(inode, pages[0], start, end, 0);
-		ret = -EIO;
-		goto out_pages;
-	}
+					  false);
 	ret = orig_count;
 	goto out;
 

fs/btrfs/lzo.c

@@ -17,6 +17,7 @@
 #include "compression.h"
 #include "ctree.h"
 #include "super.h"
+#include "btrfs_inode.h"
 
 #define LZO_LEN	4
 
@@ -329,7 +330,7 @@ static void copy_compressed_segment(struct compressed_bio *cb,
 int lzo_decompress_bio(struct list_head *ws, struct compressed_bio *cb)
 {
 	struct workspace *workspace = list_entry(ws, struct workspace, list);
-	const struct btrfs_fs_info *fs_info = btrfs_sb(cb->inode->i_sb);
+	const struct btrfs_fs_info *fs_info = cb->bbio.inode->root->fs_info;
 	const u32 sectorsize = fs_info->sectorsize;
 	char *kaddr;
 	int ret;