[PATCH 12/15] btrfs: Use iomap_dio_rw for performing direct I/O writes

From: Goldwyn Rodrigues <rgoldwyn@suse.de>
To: linux-fsdevel@vger.kernel.org
Cc: linux-btrfs@vger.kernel.org, darrick.wong@oracle.com, hch@lst.de,
	linux-xfs@vger.kernel.org, Goldwyn Rodrigues <rgoldwyn@suse.com>
Subject: [PATCH 12/15] btrfs: Use iomap_dio_rw for performing direct I/O writes
Date: Thu,  5 Sep 2019 10:06:47 -0500	[thread overview]
Message-ID: <20190905150650.21089-13-rgoldwyn@suse.de> (raw)
In-Reply-To: <20190905150650.21089-1-rgoldwyn@suse.de>

From: Goldwyn Rodrigues <rgoldwyn@suse.com>

btrfs_iomap_init() is a function to be used to btrfs_iomap
structure which is used to pass information between iomap
begin() and end(). All data reservations and allocations must
be performed in this function. For reads, btrfs_iomap allocation
is not required.

We perform space allocation and reservation before the
iomap_dio_rw() call, as opposed to iomap_begin(). This is how
the current direct I/O path performs. The problem with putting
in the iomap_begin() is that the transaction needs to be
committed before new allocation is performed. Performing a
transaction for every direct sub-write will reduce performance.

Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.com>
---
 fs/btrfs/ctree.h |   3 ++
 fs/btrfs/file.c  |   2 +-
 fs/btrfs/inode.c |  14 +++--
 fs/btrfs/iomap.c | 158 +++++++++++++++++++++++++++++++++++++++++++++++++++++--
 4 files changed, 164 insertions(+), 13 deletions(-)

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 04c119ca229b..7f84b7e47c8a 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -3202,6 +3202,8 @@ 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);
 extern const struct dentry_operations btrfs_dentry_operations;
+void btrfs_submit_direct(struct bio *dio_bio, struct inode *inode,
+		loff_t file_offset);
 
 /* ioctl.c */
 long btrfs_ioctl(struct file *file, unsigned int cmd, unsigned long arg);
@@ -3251,6 +3253,7 @@ loff_t btrfs_remap_file_range(struct file *file_in, loff_t pos_in,
 /* iomap.c */
 size_t btrfs_buffered_iomap_write(struct kiocb *iocb, struct iov_iter *from);
 ssize_t btrfs_dio_iomap_read(struct kiocb *iocb, struct iov_iter *to);
+ssize_t btrfs_dio_iomap_write(struct kiocb *iocb, struct iov_iter *from);
 
 /* tree-defrag.c */
 int btrfs_defrag_leaves(struct btrfs_trans_handle *trans,
diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index e7f67d514ba8..5d4347e12cdc 100644
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -1501,7 +1501,7 @@ static ssize_t btrfs_file_write_iter(struct kiocb *iocb,
 		atomic_inc(&BTRFS_I(inode)->sync_writers);
 
 	if (iocb->ki_flags & IOCB_DIRECT) {
-		num_written = __btrfs_direct_write(iocb, from);
+		num_written = btrfs_dio_iomap_write(iocb, from);
 	} else {
 		num_written = btrfs_buffered_iomap_write(iocb, from);
 		if (num_written > 0)
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index d415534ce733..323d72858c9c 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -8167,9 +8167,8 @@ static void btrfs_endio_direct_read(struct bio *bio)
 	kfree(dip);
 
 	dio_bio->bi_status = err;
-	dio_end_io(dio_bio);
+	bio_endio(dio_bio);
 	btrfs_io_bio_free_csum(io_bio);
-	bio_put(bio);
 }
 
 void btrfs_update_ordered_extent(struct inode *inode,
@@ -8231,8 +8230,7 @@ static void btrfs_endio_direct_write(struct bio *bio)
 	kfree(dip);
 
 	dio_bio->bi_status = bio->bi_status;
-	dio_end_io(dio_bio);
-	bio_put(bio);
+	bio_endio(dio_bio);
 }
 
 static blk_status_t btrfs_submit_bio_start_direct_io(void *private_data,
@@ -8464,8 +8462,8 @@ static int btrfs_submit_direct_hook(struct btrfs_dio_private *dip)
 	return 0;
 }
 
-static void btrfs_submit_direct(struct bio *dio_bio, struct inode *inode,
-				loff_t file_offset)
+void btrfs_submit_direct(struct bio *dio_bio, struct inode *inode,
+			 loff_t file_offset)
 {
 	struct btrfs_dio_private *dip = NULL;
 	struct bio *bio = NULL;
@@ -8536,7 +8534,7 @@ static void btrfs_submit_direct(struct bio *dio_bio, struct inode *inode,
 		/*
 		 * The end io callbacks free our dip, do the final put on bio
 		 * and all the cleanup and final put for dio_bio (through
-		 * dio_end_io()).
+		 * end_io()).
 		 */
 		dip = NULL;
 		bio = NULL;
@@ -8555,7 +8553,7 @@ static void btrfs_submit_direct(struct bio *dio_bio, struct inode *inode,
 		 * Releases and cleans up our dio_bio, no need to bio_put()
 		 * nor bio_endio()/bio_io_error() against dio_bio.
 		 */
-		dio_end_io(dio_bio);
+		bio_endio(dio_bio);
 	}
 	if (bio)
 		bio_put(bio);
diff --git a/fs/btrfs/iomap.c b/fs/btrfs/iomap.c
index 6b633c483dba..faefcab509aa 100644
--- a/fs/btrfs/iomap.c
+++ b/fs/btrfs/iomap.c
@@ -7,6 +7,7 @@
  */
 
 #include <linux/iomap.h>
+#include <linux/uio.h>
 #include "ctree.h"
 #include "btrfs_inode.h"
 #include "volumes.h"
@@ -421,15 +422,113 @@ size_t btrfs_buffered_iomap_write(struct kiocb *iocb, struct iov_iter *from)
 	return written;
 }
 
+static struct btrfs_iomap *btrfs_iomap_init(struct inode *inode,
+		struct extent_map **em,
+		loff_t pos, loff_t length)
+{
+	int ret = 0;
+	struct extent_map *map = *em;
+	struct btrfs_iomap *bi;
+	u64 num_bytes;
+
+	bi = kzalloc(sizeof(struct btrfs_iomap), GFP_NOFS);
+	if (!bi)
+		return ERR_PTR(-ENOMEM);
+
+	bi->start = round_down(pos, PAGE_SIZE);
+	bi->end = PAGE_ALIGN(pos + length) - 1;
+	num_bytes = bi->end - bi->start + 1;
+
+	/* Wait for existing ordered extents in range to finish */
+	btrfs_wait_ordered_range(inode, bi->start, num_bytes);
+
+	lock_extent_bits(&BTRFS_I(inode)->io_tree, bi->start, bi->end, &bi->cached_state);
+
+	if (ret) {
+		unlock_extent_cached(&BTRFS_I(inode)->io_tree, bi->start, bi->end,
+				&bi->cached_state);
+		kfree(bi);
+		return ERR_PTR(ret);
+	}
+
+	refcount_inc(&map->refs);
+	ret = btrfs_get_extent_map_write(em, NULL,
+			inode, bi->start, num_bytes);
+	if (ret) {
+		unlock_extent_cached(&BTRFS_I(inode)->io_tree, bi->start, bi->end,
+				&bi->cached_state);
+		kfree(bi);
+		return ERR_PTR(ret);
+	}
+	free_extent_map(map);
+	return bi;
+}
+
 static int btrfs_dio_iomap_begin(struct inode *inode, loff_t pos,
-		loff_t length, unsigned flags, struct iomap *iomap,
-		struct iomap *srcmap)
+                loff_t length, unsigned flags, struct iomap *iomap,
+                struct iomap *srcmap)
+{
+        struct extent_map *em;
+        struct btrfs_iomap *bi = NULL;
+
+        em = btrfs_get_extent(BTRFS_I(inode), NULL, 0, pos, length, 0);
+
+        if (flags & IOMAP_WRITE) {
+                srcmap->offset = em->start;
+                srcmap->length = em->len;
+                srcmap->bdev = em->bdev;
+                if (em->block_start == EXTENT_MAP_HOLE) {
+                        srcmap->type = IOMAP_HOLE;
+                } else {
+                        srcmap->type = IOMAP_MAPPED;
+                        srcmap->addr = em->block_start;
+                }
+                bi = btrfs_iomap_init(inode, &em, pos, length);
+                if (IS_ERR(bi))
+                        return PTR_ERR(bi);
+        }
+
+        iomap->offset = em->start;
+        iomap->length = em->len;
+        iomap->bdev = em->bdev;
+
+	if (em->block_start == EXTENT_MAP_HOLE) {
+		iomap->type = IOMAP_HOLE;
+	} else {
+		iomap->type = IOMAP_MAPPED;
+		iomap->addr = em->block_start;
+	}
+        iomap->private = bi;
+        return 0;
+}
+
+static int btrfs_dio_iomap_end(struct inode *inode, loff_t pos,
+		loff_t length, ssize_t written, unsigned flags,
+		struct iomap *iomap)
 {
-	return get_iomap(inode, pos, length, iomap);
+	struct btrfs_iomap *bi = iomap->private;
+	u64 wend;
+	loff_t release_bytes;
+
+	if (!bi)
+		return 0;
+
+	unlock_extent_cached(&BTRFS_I(inode)->io_tree, bi->start, bi->end,
+			&bi->cached_state);
+
+	wend = PAGE_ALIGN(pos + written);
+	release_bytes = wend - bi->end - 1;
+	kfree(bi);
+	return 0;
 }
 
 static const struct iomap_ops btrfs_dio_iomap_ops = {
 	.iomap_begin            = btrfs_dio_iomap_begin,
+	.iomap_end              = btrfs_dio_iomap_end,
+};
+
+static const struct iomap_dio_ops btrfs_dops = {
+	.submit_io = btrfs_submit_direct,
 };
 
 ssize_t btrfs_dio_iomap_read(struct kiocb *iocb, struct iov_iter *to)
@@ -437,7 +536,58 @@ ssize_t btrfs_dio_iomap_read(struct kiocb *iocb, struct iov_iter *to)
 	struct inode *inode = file_inode(iocb->ki_filp);
 	ssize_t ret;
 	inode_lock_shared(inode);
-	ret = iomap_dio_rw(iocb, to, &btrfs_dio_iomap_ops, NULL);
+	ret = iomap_dio_rw(iocb, to, &btrfs_dio_iomap_ops, &btrfs_dops);
 	inode_unlock_shared(inode);
 	return ret;
 }
+
+ssize_t btrfs_dio_iomap_write(struct kiocb *iocb, struct iov_iter *from)
+{
+	struct file *file = iocb->ki_filp;
+	struct inode *inode = file_inode(file);
+	ssize_t written, written_buffered;
+	loff_t pos = iocb->ki_pos, endbyte;
+	size_t count = iov_iter_count(from);
+	struct extent_changeset *data_reserved = NULL;
+	int err;
+
+	btrfs_delalloc_reserve_space(inode, &data_reserved, pos, count);
+
+	written = iomap_dio_rw(iocb, from, &btrfs_dio_iomap_ops, &btrfs_dops);
+	if (written < count) {
+		ssize_t done = (written < 0) ? 0 : written;
+		btrfs_delalloc_release_space(inode, data_reserved, pos, count - done,
+	                       true);
+	}
+	btrfs_delalloc_release_extents(BTRFS_I(inode), count, false);
+	extent_changeset_free(data_reserved);
+
+	if (written < 0 || !iov_iter_count(from))
+		return written;
+
+	pos = iocb->ki_pos;
+	written_buffered = btrfs_buffered_iomap_write(iocb, from);
+	if (written_buffered < 0) {
+		err = written_buffered;
+		goto out;
+	}
+	/*
+	 * Ensure all data is persisted. We want the next direct IO read to be
+	 * able to read what was just written.
+	 */
+	endbyte = pos + written_buffered - 1;
+	err = btrfs_fdatawrite_range(inode, pos, endbyte);
+	if (err)
+		goto out;
+	err = filemap_fdatawait_range(inode->i_mapping, pos, endbyte);
+	if (err)
+		goto out;
+	written += written_buffered;
+	iocb->ki_pos = pos + written_buffered;
+	invalidate_mapping_pages(file->f_mapping, pos >> PAGE_SHIFT,
+			endbyte >> PAGE_SHIFT);
+out:
+	if (written > 0 && iocb->ki_pos > i_size_read(inode))
+			i_size_write(inode, iocb->ki_pos);
+	return written ? written : err;
+}
-- 
2.16.4

