From: Omar Sandoval <redacted>

The implementation resembles direct I/O: we have to flush any ordered
extents, invalidate the page cache, and do the io tree/delalloc/extent
map/ordered extent dance. From there, we can reuse the compression code
with a minor modification to distinguish the write from writeback. This
also creates inline extents when possible.

Now that read and write are implemented, this also sets the
FMODE_ENCODED_IO flag in btrfs_file_open().

Signed-off-by: Omar Sandoval <redacted>
---
  fs/btrfs/compression.c  |   7 +-
  fs/btrfs/compression.h  |   6 +-
  fs/btrfs/ctree.h        |   2 +
  fs/btrfs/file.c         |  37 +++++-
  fs/btrfs/inode.c        | 259 +++++++++++++++++++++++++++++++++++++++-
  fs/btrfs/ordered-data.c |  12 +-
  fs/btrfs/ordered-data.h |   2 +
  7 files changed, 313 insertions(+), 12 deletions(-)

diff --git a/fs/btrfs/compression.c b/fs/btrfs/compression.c
index eaa6fe21c08e..015c9e5d75b9 100644
--- a/fs/btrfs/compression.c
+++ b/fs/btrfs/compression.c

@@ -336,7 +336,8 @@ static void end_compressed_bio_write(struct bio *bio)
  			bio->bi_status == BLK_STS_OK);
  	cb->compressed_pages[0]->mapping = NULL;
  
-	end_compressed_writeback(inode, cb);
+	if (cb->writeback)
+		end_compressed_writeback(inode, cb);
  	/* note, our inode could be gone now */
  
  	/*

@@ -372,7 +373,8 @@ blk_status_t btrfs_submit_compressed_write(struct btrfs_inode *inode, u64 start,
  				 struct page **compressed_pages,
  				 unsigned long nr_pages,
  				 unsigned int write_flags,
-				 struct cgroup_subsys_state *blkcg_css)
+				 struct cgroup_subsys_state *blkcg_css,
+				 bool writeback)
  {
  	struct btrfs_fs_info *fs_info = inode->root->fs_info;
  	struct bio *bio = NULL;

@@ -396,6 +398,7 @@ blk_status_t btrfs_submit_compressed_write(struct btrfs_inode *inode, u64 start,
  	cb->mirror_num = 0;
  	cb->compressed_pages = compressed_pages;
  	cb->compressed_len = compressed_len;
+	cb->writeback = writeback;
  	cb->orig_bio = NULL;
  	cb->nr_pages = nr_pages;
  

diff --git a/fs/btrfs/compression.h b/fs/btrfs/compression.h
index 8001b700ea3a..f95cdc16f503 100644
--- a/fs/btrfs/compression.h
+++ b/fs/btrfs/compression.h

@@ -49,6 +49,9 @@ struct compressed_bio {
  	/* the compression algorithm for this bio */
  	int compress_type;
  
+	/* Whether this is a write for writeback. */
+	bool writeback;
+
  	/* number of compressed pages in the array */
  	unsigned long nr_pages;
  

@@ -96,7 +99,8 @@ blk_status_t btrfs_submit_compressed_write(struct btrfs_inode *inode, u64 start,
  				  struct page **compressed_pages,
  				  unsigned long nr_pages,
  				  unsigned int write_flags,
-				  struct cgroup_subsys_state *blkcg_css);
+				  struct cgroup_subsys_state *blkcg_css,
+				  bool writeback);
  blk_status_t btrfs_submit_compressed_read(struct inode *inode, struct bio *bio,
  				 int mirror_num, unsigned long bio_flags);
  

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index ce78424f1d98..9b585ac9c7a9 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h

@@ -3134,6 +3134,8 @@ int btrfs_writepage_cow_fixup(struct page *page, u64 start, u64 end);
  void btrfs_writepage_endio_finish_ordered(struct page *page, u64 start,
  					  u64 end, int uptodate);
  ssize_t btrfs_encoded_read(struct kiocb *iocb, struct iov_iter *iter);
+ssize_t btrfs_do_encoded_write(struct kiocb *iocb, struct iov_iter *from,
+			       struct encoded_iov *encoded);
  
  extern const struct dentry_operations btrfs_dentry_operations;
  extern const struct iomap_ops btrfs_dio_iomap_ops;

diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index 193477565200..f815ffb93d43 100644
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c

@@ -1994,6 +1994,32 @@ static ssize_t btrfs_direct_write(struct kiocb *iocb, struct iov_iter *from)
  	return written ? written : err;
  }
  
+static ssize_t btrfs_encoded_write(struct kiocb *iocb, struct iov_iter *from)
+{
+	struct file *file = iocb->ki_filp;
+	struct inode *inode = file_inode(file);
+	struct encoded_iov encoded;
+	ssize_t ret;
+
+	ret = copy_encoded_iov_from_iter(&encoded, from);
+	if (ret)
+		return ret;
+
+	btrfs_inode_lock(inode, 0);
+	ret = generic_encoded_write_checks(iocb, &encoded);
+	if (ret || encoded.len == 0)
+		goto out;
+
+	ret = btrfs_write_check(iocb, from, encoded.len);
+	if (ret < 0)
+		goto out;
+
+	ret = btrfs_do_encoded_write(iocb, from, &encoded);
+out:
+	btrfs_inode_unlock(inode, 0);
+	return ret;
+}
+
  static ssize_t btrfs_file_write_iter(struct kiocb *iocb,
  				    struct iov_iter *from)
  {

@@ -2012,14 +2038,17 @@ static ssize_t btrfs_file_write_iter(struct kiocb *iocb,
  	if (test_bit(BTRFS_FS_STATE_ERROR, &fs_info->fs_state))
  		return -EROFS;
  
-	if (!(iocb->ki_flags & IOCB_DIRECT) &&
-	    (iocb->ki_flags & IOCB_NOWAIT))
+	if ((iocb->ki_flags & IOCB_NOWAIT) &&
+	    (!(iocb->ki_flags & IOCB_DIRECT) ||
+	     (iocb->ki_flags & IOCB_ENCODED)))
  		return -EOPNOTSUPP;
  
  	if (sync)
  		atomic_inc(&BTRFS_I(inode)->sync_writers);
  
-	if (iocb->ki_flags & IOCB_DIRECT)
+	if (iocb->ki_flags & IOCB_ENCODED)
+		num_written = btrfs_encoded_write(iocb, from);
+	else if (iocb->ki_flags & IOCB_DIRECT)
  		num_written = btrfs_direct_write(iocb, from);
  	else
  		num_written = btrfs_buffered_write(iocb, from);

@@ -3586,7 +3615,7 @@ static loff_t btrfs_file_llseek(struct file *file, loff_t offset, int whence)
  
  static int btrfs_file_open(struct inode *inode, struct file *filp)
  {
-	filp->f_mode |= FMODE_NOWAIT | FMODE_BUF_RASYNC;
+	filp->f_mode |= FMODE_NOWAIT | FMODE_BUF_RASYNC | FMODE_ENCODED_IO;
  	return generic_file_open(inode, filp);
  }
  

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index b0e800897b3b..2bf7b487939f 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c

@@ -935,7 +935,7 @@ static noinline void submit_compressed_extents(struct async_chunk *async_chunk)
  				    ins.offset, async_extent->pages,
  				    async_extent->nr_pages,
  				    async_chunk->write_flags,
-				    async_chunk->blkcg_css)) {
+				    async_chunk->blkcg_css, true)) {
  			struct page *p = async_extent->pages[0];
  			const u64 start = async_extent->start;
  			const u64 end = start + async_extent->ram_size - 1;

@@ -2703,6 +2703,7 @@ static int insert_ordered_extent_file_extent(struct btrfs_trans_handle *trans,
  	 * except if the ordered extent was truncated.
  	 */
  	update_inode_bytes = test_bit(BTRFS_ORDERED_DIRECT, &oe->flags) ||
+	                     test_bit(BTRFS_ORDERED_ENCODED, &oe->flags) ||