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>

1 files changed, 7 insertions, 10 deletions

diff --git a/fs/btrfs/compression.h b/fs/btrfs/compression.h
index a5e3377db9ad..95d2e85c6e4e 100644
--- a/fs/btrfs/compression.h
+++ b/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);