Commit 769b4f24 authored by Omar Sandoval's avatar Omar Sandoval Committed by David Sterba
Browse files

btrfs: get rid of one layer of bios in direct I/O 



In the worst case, there are _4_ layers of bios in the Btrfs direct I/O
path:

1. The bio created by the generic direct I/O code (dio_bio).
2. A clone of dio_bio we create in btrfs_submit_direct() to represent
   the entire direct I/O range (orig_bio).
3. A partial clone of orig_bio limited to the size of a RAID stripe that
   we create in btrfs_submit_direct_hook().
4. Clones of each of those split bios for each RAID stripe that we
   create in btrfs_map_bio().

As of the previous commit, the second layer (orig_bio) is no longer
needed for anything: we can split dio_bio instead, and complete dio_bio
directly when all of the cloned bios complete. This lets us clean up a
bunch of cruft, including dip->subio_endio and dip->errors (we can use
dio_bio->bi_status instead). It also enables the next big cleanup of
direct I/O read repair.

Reviewed-by: default avatarJosef Bacik <josef@toxicpanda.com>
Signed-off-by: default avatarOmar Sandoval <osandov@fb.com>
Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
parent 85879573

fs/btrfs/btrfs_inode.h

+0 −16
Original line number Diff line number Diff line
@@ -294,11 +294,8 @@ static inline int btrfs_inode_in_log(struct btrfs_inode *inode, u64 generation) 
	return ret;

}



#define BTRFS_DIO_ORIG_BIO_SUBMITTED	0x1



struct btrfs_dio_private {

	struct inode *inode;

	unsigned long flags;

	u64 logical_offset;

	u64 disk_bytenr;

	u64 bytes;
@@ -309,22 +306,9 @@ struct btrfs_dio_private { 
	 */

	refcount_t refs;



	/* IO errors */

	int errors;



	/* orig_bio is our btrfs_io_bio */

	struct bio *orig_bio;



	/* dio_bio came from fs/direct-io.c */

	struct bio *dio_bio;



	/*

	 * The original bio may be split to several sub-bios, this is

	 * done during endio of sub-bios

	 */

	blk_status_t (*subio_endio)(struct inode *, struct btrfs_io_bio *,

			blk_status_t);



	/* Array of checksums */

	u8 csums[];

};

fs/btrfs/inode.c

+65 −120
Original line number Diff line number Diff line
@@ -7356,6 +7356,29 @@ static int btrfs_get_blocks_direct(struct inode *inode, sector_t iblock, 
	return ret;

}



static void btrfs_dio_private_put(struct btrfs_dio_private *dip)

{

	/*

	 * This implies a barrier so that stores to dio_bio->bi_status before

	 * this and loads of dio_bio->bi_status after this are fully ordered.

	 */

	if (!refcount_dec_and_test(&dip->refs))

		return;



	if (bio_op(dip->dio_bio) == REQ_OP_WRITE) {

		__endio_write_update_ordered(dip->inode, dip->logical_offset,

					     dip->bytes,

					     !dip->dio_bio->bi_status);

	} else {

		unlock_extent(&BTRFS_I(dip->inode)->io_tree,

			      dip->logical_offset,

			      dip->logical_offset + dip->bytes - 1);

	}



	dio_end_io(dip->dio_bio);

	kfree(dip);

}



static inline blk_status_t submit_dio_repair_bio(struct inode *inode,

						 struct bio *bio,

						 int mirror_num)
@@ -7678,8 +7701,9 @@ static blk_status_t __btrfs_subio_endio_read(struct inode *inode, 
	return err;

}



static blk_status_t btrfs_subio_endio_read(struct inode *inode,

		struct btrfs_io_bio *io_bio, blk_status_t err)

static blk_status_t btrfs_check_read_dio_bio(struct inode *inode,

					     struct btrfs_io_bio *io_bio,

					     blk_status_t err)

{

	bool skip_csum = BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM;
@@ -7693,28 +7717,6 @@ static blk_status_t btrfs_subio_endio_read(struct inode *inode, 
	}

}



static void btrfs_endio_direct_read(struct bio *bio)

{

	struct btrfs_dio_private *dip = bio->bi_private;

	struct inode *inode = dip->inode;

	struct bio *dio_bio;

	struct btrfs_io_bio *io_bio = btrfs_io_bio(bio);

	blk_status_t err = bio->bi_status;



	if (dip->flags & BTRFS_DIO_ORIG_BIO_SUBMITTED)

		err = btrfs_subio_endio_read(inode, io_bio, err);



	unlock_extent(&BTRFS_I(inode)->io_tree, dip->logical_offset,

		      dip->logical_offset + dip->bytes - 1);

	dio_bio = dip->dio_bio;



	kfree(dip);



	dio_bio->bi_status = err;

	dio_end_io(dio_bio);

	bio_put(bio);

}



static void __endio_write_update_ordered(struct inode *inode,

					 const u64 offset, const u64 bytes,

					 const bool uptodate)
@@ -7758,21 +7760,6 @@ static void __endio_write_update_ordered(struct inode *inode, 
	}

}



static void btrfs_endio_direct_write(struct bio *bio)

{

	struct btrfs_dio_private *dip = bio->bi_private;

	struct bio *dio_bio = dip->dio_bio;



	__endio_write_update_ordered(dip->inode, dip->logical_offset,

				     dip->bytes, !bio->bi_status);



	kfree(dip);



	dio_bio->bi_status = bio->bi_status;

	dio_end_io(dio_bio);

	bio_put(bio);

}



static blk_status_t btrfs_submit_bio_start_direct_io(void *private_data,

				    struct bio *bio, u64 offset)

{
@@ -7796,31 +7783,16 @@ static void btrfs_end_dio_bio(struct bio *bio) 
			   (unsigned long long)bio->bi_iter.bi_sector,

			   bio->bi_iter.bi_size, err);



	if (dip->subio_endio)

		err = dip->subio_endio(dip->inode, btrfs_io_bio(bio), err);



	if (err) {

		/*

		 * We want to perceive the errors flag being set before

		 * decrementing the reference count. We don't need a barrier

		 * since atomic operations with a return value are fully

		 * ordered as per atomic_t.txt

		 */

		dip->errors = 1;

	if (bio_op(bio) == REQ_OP_READ) {

		err = btrfs_check_read_dio_bio(dip->inode, btrfs_io_bio(bio),

					       err);

	}



	/* if there are more bios still pending for this dio, just exit */

	if (!refcount_dec_and_test(&dip->refs))

		goto out;

	if (err)

		dip->dio_bio->bi_status = err;



	if (dip->errors) {

		bio_io_error(dip->orig_bio);

	} else {

		dip->dio_bio->bi_status = BLK_STS_OK;

		bio_endio(dip->orig_bio);

	}

out:

	bio_put(bio);

	btrfs_dio_private_put(dip);

}



static inline blk_status_t btrfs_submit_dio_bio(struct bio *bio,
@@ -7883,7 +7855,6 @@ static struct btrfs_dio_private *btrfs_create_dio_private(struct bio *dio_bio, 
	const bool csum = !(BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM);

	size_t dip_size;

	struct btrfs_dio_private *dip;

	struct bio *bio;



	dip_size = sizeof(*dip);

	if (!write && csum) {
@@ -7899,15 +7870,10 @@ static struct btrfs_dio_private *btrfs_create_dio_private(struct bio *dio_bio, 
	if (!dip)

		return NULL;



	bio = btrfs_bio_clone(dio_bio);

	bio->bi_private = dip;

	btrfs_io_bio(bio)->logical = file_offset;



	dip->inode = inode;

	dip->logical_offset = file_offset;

	dip->bytes = dio_bio->bi_iter.bi_size;

	dip->disk_bytenr = (u64)dio_bio->bi_iter.bi_sector << 9;

	dip->orig_bio = bio;

	dip->dio_bio = dio_bio;

	refcount_set(&dip->refs, 1);
@@ -7922,11 +7888,6 @@ static struct btrfs_dio_private *btrfs_create_dio_private(struct bio *dio_bio, 
			dip->bytes;

		dio_data->unsubmitted_oe_range_start =

			dio_data->unsubmitted_oe_range_end;



		bio->bi_end_io = btrfs_endio_direct_write;

	} else {

		bio->bi_end_io = btrfs_endio_direct_read;

		dip->subio_endio = btrfs_subio_endio_read;

	}

	return dip;

}
@@ -7937,9 +7898,10 @@ static void btrfs_submit_direct(struct bio *dio_bio, struct inode *inode, 
	const bool write = (bio_op(dio_bio) == REQ_OP_WRITE);

	const bool csum = !(BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM);

	struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);

	const bool raid56 = (btrfs_data_alloc_profile(fs_info) &

			     BTRFS_BLOCK_GROUP_RAID56_MASK);

	struct btrfs_dio_private *dip;

	struct bio *bio;

	struct bio *orig_bio;

	u64 start_sector;

	int async_submit = 0;

	u64 submit_len;
@@ -7971,58 +7933,59 @@ static void btrfs_submit_direct(struct bio *dio_bio, struct inode *inode, 
			goto out_err;

	}



	orig_bio = dip->orig_bio;

	start_sector = orig_bio->bi_iter.bi_sector;

	submit_len = orig_bio->bi_iter.bi_size;

	ret = btrfs_get_io_geometry(fs_info, btrfs_op(orig_bio),

				    start_sector << 9, submit_len, &geom);

	if (ret)

		goto out_err;

	start_sector = dio_bio->bi_iter.bi_sector;

	submit_len = dio_bio->bi_iter.bi_size;



	if (geom.len >= submit_len) {

		bio = orig_bio;

		dip->flags |= BTRFS_DIO_ORIG_BIO_SUBMITTED;

		goto submit;

	do {

		ret = btrfs_get_io_geometry(fs_info, btrfs_op(dio_bio),

					    start_sector << 9, submit_len,

					    &geom);

		if (ret) {

			status = errno_to_blk_status(ret);

			goto out_err;

		}



	/* async crcs make it difficult to collect full stripe writes. */

	if (btrfs_data_alloc_profile(fs_info) & BTRFS_BLOCK_GROUP_RAID56_MASK)

		async_submit = 0;

	else

		async_submit = 1;



	/* bio split */

		ASSERT(geom.len <= INT_MAX);

	do {



		clone_len = min_t(int, submit_len, geom.len);



		/*

		 * This will never fail as it's passing GPF_NOFS and

		 * the allocation is backed by btrfs_bioset.

		 */

		bio = btrfs_bio_clone_partial(orig_bio, clone_offset,

					      clone_len);

		bio = btrfs_bio_clone_partial(dio_bio, clone_offset, clone_len);

		bio->bi_private = dip;

		bio->bi_end_io = btrfs_end_dio_bio;

		btrfs_io_bio(bio)->logical = file_offset;



		ASSERT(submit_len >= clone_len);

		submit_len -= clone_len;

		if (submit_len == 0)

			break;



		/*

		 * Increase the count before we submit the bio so we know

		 * the end IO handler won't happen before we increase the

		 * count. Otherwise, the dip might get freed before we're

		 * done setting it up.

		 *

		 * We transfer the initial reference to the last bio, so we

		 * don't need to increment the reference count for the last one.

		 */

		if (submit_len > 0) {

			refcount_inc(&dip->refs);

			/*

			 * If we are submitting more than one bio, submit them

			 * all asynchronously. The exception is RAID 5 or 6, as

			 * asynchronous checksums make it difficult to collect

			 * full stripe writes.

			 */

			if (!raid56)

				async_submit = 1;

		}



		status = btrfs_submit_dio_bio(bio, inode, file_offset,

						async_submit);

		if (status) {

			bio_put(bio);

			if (submit_len > 0)

				refcount_dec(&dip->refs);

			goto out_err;

		}
@@ -8030,30 +7993,12 @@ static void btrfs_submit_direct(struct bio *dio_bio, struct inode *inode, 
		clone_offset += clone_len;

		start_sector += clone_len >> 9;

		file_offset += clone_len;



		ret = btrfs_get_io_geometry(fs_info, btrfs_op(orig_bio),

				      start_sector << 9, submit_len, &geom);

		if (ret)

			goto out_err;

	} while (submit_len > 0);



submit:

	status = btrfs_submit_dio_bio(bio, inode, file_offset, async_submit);

	if (!status)

	return;



	if (bio != orig_bio)

		bio_put(bio);

out_err:

	dip->errors = 1;

	/*

	 * Before atomic variable goto zero, we must  make sure dip->errors is

	 * perceived to be set. This ordering is ensured by the fact that an

	 * atomic operations with a return value are fully ordered as per

	 * atomic_t.txt

	 */

	if (refcount_dec_and_test(&dip->refs))

		bio_io_error(dip->orig_bio);

	dip->dio_bio->bi_status = status;

	btrfs_dio_private_put(dip);

}



static ssize_t check_direct_IO(struct btrfs_fs_info *fs_info,