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From: Stefan Roesch <[email protected]>
To: <[email protected]>, <[email protected]>,
	<[email protected]>, <[email protected]>,
	<[email protected]>
Cc: <[email protected]>, <[email protected]>, <[email protected]>, <[email protected]>
Subject: [PATCH v6 05/16] iomap: Add async buffered write support
Date: Thu, 26 May 2022 10:38:29 -0700	[thread overview]
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>

This adds async buffered write support to iomap.

This replaces the call to balance_dirty_pages_ratelimited() with the
call to balance_dirty_pages_ratelimited_flags. This allows to specify if
the write request is async or not.

In addition this also moves the above function call to the beginning of
the function. If the function call is at the end of the function and the
decision is made to throttle writes, then there is no request that
io-uring can wait on. By moving it to the beginning of the function, the
write request is not issued, but returns -EAGAIN instead. io-uring will
punt the request and process it in the io-worker.

By moving the function call to the beginning of the function, the write
throttling will happen one page later.

Signed-off-by: Stefan Roesch <[email protected]>
Reviewed-by: Jan Kara <[email protected]>
---
 fs/iomap/buffered-io.c | 31 +++++++++++++++++++++++++++----
 1 file changed, 27 insertions(+), 4 deletions(-)

diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
index d6ddc54e190e..2281667646d2 100644
--- a/fs/iomap/buffered-io.c
+++ b/fs/iomap/buffered-io.c
@@ -559,6 +559,7 @@ static int __iomap_write_begin(const struct iomap_iter *iter, loff_t pos,
 	loff_t block_size = i_blocksize(iter->inode);
 	loff_t block_start = round_down(pos, block_size);
 	loff_t block_end = round_up(pos + len, block_size);
+	unsigned int nr_blocks = i_blocks_per_folio(iter->inode, folio);
 	size_t from = offset_in_folio(folio, pos), to = from + len;
 	size_t poff, plen;
 
@@ -567,6 +568,8 @@ static int __iomap_write_begin(const struct iomap_iter *iter, loff_t pos,
 	folio_clear_error(folio);
 
 	iop = iomap_page_create(iter->inode, folio, iter->flags);
+	if ((iter->flags & IOMAP_NOWAIT) && !iop && nr_blocks > 1)
+		return -EAGAIN;
 
 	do {
 		iomap_adjust_read_range(iter->inode, folio, &block_start,
@@ -584,7 +587,12 @@ static int __iomap_write_begin(const struct iomap_iter *iter, loff_t pos,
 				return -EIO;
 			folio_zero_segments(folio, poff, from, to, poff + plen);
 		} else {
-			int status = iomap_read_folio_sync(block_start, folio,
+			int status;
+
+			if (iter->flags & IOMAP_NOWAIT)
+				return -EAGAIN;
+
+			status = iomap_read_folio_sync(block_start, folio,
 					poff, plen, srcmap);
 			if (status)
 				return status;
@@ -613,6 +621,9 @@ static int iomap_write_begin(const struct iomap_iter *iter, loff_t pos,
 	unsigned fgp = FGP_LOCK | FGP_WRITE | FGP_CREAT | FGP_STABLE | FGP_NOFS;
 	int status = 0;
 
+	if (iter->flags & IOMAP_NOWAIT)
+		fgp |= FGP_NOWAIT;
+
 	BUG_ON(pos + len > iter->iomap.offset + iter->iomap.length);
 	if (srcmap != &iter->iomap)
 		BUG_ON(pos + len > srcmap->offset + srcmap->length);
@@ -750,6 +761,8 @@ static loff_t iomap_write_iter(struct iomap_iter *iter, struct iov_iter *i)
 	loff_t pos = iter->pos;
 	ssize_t written = 0;
 	long status = 0;
+	struct address_space *mapping = iter->inode->i_mapping;
+	unsigned int bdp_flags = (iter->flags & IOMAP_NOWAIT) ? BDP_ASYNC : 0;
 
 	do {
 		struct folio *folio;
@@ -762,6 +775,11 @@ static loff_t iomap_write_iter(struct iomap_iter *iter, struct iov_iter *i)
 		bytes = min_t(unsigned long, PAGE_SIZE - offset,
 						iov_iter_count(i));
 again:
+		status = balance_dirty_pages_ratelimited_flags(mapping,
+							       bdp_flags);
+		if (unlikely(status))
+			break;
+
 		if (bytes > length)
 			bytes = length;
 
@@ -770,6 +788,10 @@ static loff_t iomap_write_iter(struct iomap_iter *iter, struct iov_iter *i)
 		 * Otherwise there's a nasty deadlock on copying from the
 		 * same page as we're writing to, without it being marked
 		 * up-to-date.
+		 *
+		 * For async buffered writes the assumption is that the user
+		 * page has already been faulted in. This can be optimized by
+		 * faulting the user page in the prepare phase of io-uring.
 		 */
 		if (unlikely(fault_in_iov_iter_readable(i, bytes) == bytes)) {
 			status = -EFAULT;
@@ -781,7 +803,7 @@ static loff_t iomap_write_iter(struct iomap_iter *iter, struct iov_iter *i)
 			break;
 
 		page = folio_file_page(folio, pos >> PAGE_SHIFT);
-		if (mapping_writably_mapped(iter->inode->i_mapping))
+		if (mapping_writably_mapped(mapping))
 			flush_dcache_page(page);
 
 		copied = copy_page_from_iter_atomic(page, offset, bytes, i);
@@ -806,8 +828,6 @@ static loff_t iomap_write_iter(struct iomap_iter *iter, struct iov_iter *i)
 		pos += status;
 		written += status;
 		length -= status;
-
-		balance_dirty_pages_ratelimited(iter->inode->i_mapping);
 	} while (iov_iter_count(i) && length);
 
 	return written ? written : status;
@@ -825,6 +845,9 @@ iomap_file_buffered_write(struct kiocb *iocb, struct iov_iter *i,
 	};
 	int ret;
 
+	if (iocb->ki_flags & IOCB_NOWAIT)
+		iter.flags |= IOMAP_NOWAIT;
+
 	while ((ret = iomap_iter(&iter, ops)) > 0)
 		iter.processed = iomap_write_iter(&iter, i);
 	if (iter.pos == iocb->ki_pos)
-- 
2.30.2



  parent reply	other threads:[~2022-05-26 17:39 UTC|newest]

Thread overview: 30+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-05-26 17:38 [PATCH v6 00/16] io-uring/xfs: support async buffered writes Stefan Roesch
2022-05-26 17:38 ` [PATCH v6 01/16] mm: Move starting of background writeback into the main balancing loop Stefan Roesch
2022-05-26 17:38 ` [PATCH v6 02/16] mm: Move updates of dirty_exceeded into one place Stefan Roesch
2022-05-26 17:38 ` [PATCH v6 03/16] mm: Add balance_dirty_pages_ratelimited_flags() function Stefan Roesch
2022-05-31  6:52   ` Christoph Hellwig
2022-05-26 17:38 ` [PATCH v6 04/16] iomap: Add flags parameter to iomap_page_create() Stefan Roesch
2022-05-26 18:25   ` Darrick J. Wong
2022-05-26 18:43     ` Stefan Roesch
     [not found]   ` <[email protected]>
2022-05-31 18:12     ` Stefan Roesch
2022-05-26 17:38 ` Stefan Roesch [this message]
2022-05-26 18:42   ` [PATCH v6 05/16] iomap: Add async buffered write support Darrick J. Wong
2022-05-26 22:37   ` Dave Chinner
2022-05-27  8:42     ` Jan Kara
2022-05-27 22:52       ` Dave Chinner
2022-05-31  7:55         ` Jan Kara
2022-05-26 17:38 ` [PATCH v6 06/16] fs: Add check for async buffered writes to generic_write_checks Stefan Roesch
2022-05-31  6:59   ` Christoph Hellwig
2022-05-26 17:38 ` [PATCH v6 07/16] fs: add __remove_file_privs() with flags parameter Stefan Roesch
2022-05-26 17:38 ` [PATCH v6 08/16] fs: Split off inode_needs_update_time and __file_update_time Stefan Roesch
2022-05-26 17:38 ` [PATCH v6 09/16] fs: Add async write file modification handling Stefan Roesch
2022-05-26 17:38 ` [PATCH v6 10/16] fs: Optimization for concurrent file time updates Stefan Roesch
2022-05-26 17:38 ` [PATCH v6 11/16] io_uring: Add support for async buffered writes Stefan Roesch
2022-05-26 17:38 ` [PATCH v6 12/16] io_uring: Add tracepoint for short writes Stefan Roesch
2022-05-26 17:38 ` [PATCH v6 13/16] xfs: Specify lockmode when calling xfs_ilock_for_iomap() Stefan Roesch
2022-05-31  7:03   ` Christoph Hellwig
2022-05-26 17:38 ` [PATCH v6 14/16] xfs: Change function signature of xfs_ilock_iocb() Stefan Roesch
2022-05-31  7:04   ` Christoph Hellwig
2022-05-26 17:38 ` [PATCH v6 15/16] xfs: Add async buffered write support Stefan Roesch
2022-05-31  7:05   ` Christoph Hellwig
2022-05-26 17:38 ` [PATCH v6 16/16] xfs: Enable " Stefan Roesch

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