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From: Christoph Hellwig <hch@lst.de>
To: "Darrick J. Wong" <djwong@kernel.org>
Cc: Dan Williams <dan.j.williams@intel.com>,
	Matthew Wilcox <willy@infradead.org>,
	Andreas Gruenbacher <agruenba@redhat.com>,
	Shiyang Ruan <ruansy.fnst@fujitsu.com>,
	linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org,
	linux-btrfs@vger.kernel.org, nvdimm@lists.linux.dev,
	cluster-devel@redhat.com
Subject: [PATCH 08/27] iomap: add the new iomap_iter model
Date: Mon, 19 Jul 2021 12:35:01 +0200	[thread overview]
Message-ID: <20210719103520.495450-9-hch@lst.de> (raw)
In-Reply-To: <20210719103520.495450-1-hch@lst.de>

The iomap_iter struct provides a convenient way to package up and
maintain all the arguments to the various mapping and operation
functions.  It is operated on using the iomap_iter() function that
is called in loop until the whole range has been processed.  Compared
to the existing iomap_apply() function this avoid an indirect call
for each iteration.

For now iomap_iter() calls back into the existing ->iomap_begin and
->iomap_end methods, but in the future this could be further optimized
to avoid indirect calls entirely.

Based on an earlier patch from Matthew Wilcox <willy@infradead.org>.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 fs/iomap/Makefile     |  1 +
 fs/iomap/iter.c       | 74 +++++++++++++++++++++++++++++++++++++++++++
 fs/iomap/trace.h      | 37 +++++++++++++++++++++-
 include/linux/iomap.h | 56 ++++++++++++++++++++++++++++++++
 4 files changed, 167 insertions(+), 1 deletion(-)
 create mode 100644 fs/iomap/iter.c

diff --git a/fs/iomap/Makefile b/fs/iomap/Makefile
index eef2722d93a183..85034deb5a2f19 100644
--- a/fs/iomap/Makefile
+++ b/fs/iomap/Makefile
@@ -10,6 +10,7 @@ obj-$(CONFIG_FS_IOMAP)		+= iomap.o
 
 iomap-y				+= trace.o \
 				   apply.o \
+				   iter.o \
 				   buffered-io.o \
 				   direct-io.o \
 				   fiemap.o \
diff --git a/fs/iomap/iter.c b/fs/iomap/iter.c
new file mode 100644
index 00000000000000..b21e2489700b7c
--- /dev/null
+++ b/fs/iomap/iter.c
@@ -0,0 +1,74 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (c) 2021 Christoph Hellwig.
+ */
+#include <linux/fs.h>
+#include <linux/iomap.h>
+#include "trace.h"
+
+static inline int iomap_iter_advance(struct iomap_iter *iter)
+{
+	/* handle the previous iteration (if any) */
+	if (iter->iomap.length) {
+		if (iter->processed <= 0)
+			return iter->processed;
+		WARN_ON_ONCE(iter->processed > iomap_length(iter));
+		iter->pos += iter->processed;
+		iter->len -= iter->processed;
+		if (!iter->len)
+			return 0;
+	}
+
+	/* clear the state for the next iteration */
+	iter->processed = 0;
+	memset(&iter->iomap, 0, sizeof(iter->iomap));
+	memset(&iter->srcmap, 0, sizeof(iter->srcmap));
+	return 1;
+}
+
+static inline void iomap_iter_done(struct iomap_iter *iter)
+{
+	WARN_ON_ONCE(iter->iomap.offset > iter->pos);
+	WARN_ON_ONCE(iter->iomap.length == 0);
+	WARN_ON_ONCE(iter->iomap.offset + iter->iomap.length <= iter->pos);
+
+	trace_iomap_iter_dstmap(iter->inode, &iter->iomap);
+	if (iter->srcmap.type != IOMAP_HOLE)
+		trace_iomap_iter_srcmap(iter->inode, &iter->srcmap);
+}
+
+/**
+ * iomap_iter - iterate over a ranges in a file
+ * @iter: iteration structue
+ * @ops: iomap ops provided by the file system
+ *
+ * Iterate over file system provided contiguous ranges of blocks with the same
+ * state.  Should be called in a loop that continues as long as this function
+ * returns a positive value.  If 0 or a negative value is returned the caller
+ * should break out of the loop - a negative value is an error either from the
+ * file system or from the last iteration stored in @iter.copied.
+ */
+int iomap_iter(struct iomap_iter *iter, const struct iomap_ops *ops)
+{
+	int ret;
+
+	if (iter->iomap.length && ops->iomap_end) {
+		ret = ops->iomap_end(iter->inode, iter->pos, iomap_length(iter),
+				iter->processed > 0 ? iter->processed : 0,
+				iter->flags, &iter->iomap);
+		if (ret < 0 && !iter->processed)
+			return ret;
+	}
+
+	trace_iomap_iter(iter, ops, _RET_IP_);
+	ret = iomap_iter_advance(iter);
+	if (ret <= 0)
+		return ret;
+
+	ret = ops->iomap_begin(iter->inode, iter->pos, iter->len, iter->flags,
+			       &iter->iomap, &iter->srcmap);
+	if (ret < 0)
+		return ret;
+	iomap_iter_done(iter);
+	return 1;
+}
diff --git a/fs/iomap/trace.h b/fs/iomap/trace.h
index e9cd5cc0d6ba40..1012d7af6b689b 100644
--- a/fs/iomap/trace.h
+++ b/fs/iomap/trace.h
@@ -1,6 +1,6 @@
 /* SPDX-License-Identifier: GPL-2.0 */
 /*
- * Copyright (c) 2009-2019 Christoph Hellwig
+ * Copyright (c) 2009-2021 Christoph Hellwig
  *
  * NOTE: none of these tracepoints shall be considered a stable kernel ABI
  * as they can change at any time.
@@ -140,6 +140,8 @@ DEFINE_EVENT(iomap_class, name,	\
 	TP_ARGS(inode, iomap))
 DEFINE_IOMAP_EVENT(iomap_apply_dstmap);
 DEFINE_IOMAP_EVENT(iomap_apply_srcmap);
+DEFINE_IOMAP_EVENT(iomap_iter_dstmap);
+DEFINE_IOMAP_EVENT(iomap_iter_srcmap);
 
 TRACE_EVENT(iomap_apply,
 	TP_PROTO(struct inode *inode, loff_t pos, loff_t length,
@@ -179,6 +181,39 @@ TRACE_EVENT(iomap_apply,
 		   __entry->actor)
 );
 
+TRACE_EVENT(iomap_iter,
+	TP_PROTO(struct iomap_iter *iter, const void *ops,
+		 unsigned long caller),
+	TP_ARGS(iter, ops, caller),
+	TP_STRUCT__entry(
+		__field(dev_t, dev)
+		__field(u64, ino)
+		__field(loff_t, pos)
+		__field(loff_t, length)
+		__field(unsigned int, flags)
+		__field(const void *, ops)
+		__field(unsigned long, caller)
+	),
+	TP_fast_assign(
+		__entry->dev = iter->inode->i_sb->s_dev;
+		__entry->ino = iter->inode->i_ino;
+		__entry->pos = iter->pos;
+		__entry->length = iomap_length(iter);
+		__entry->flags = iter->flags;
+		__entry->ops = ops;
+		__entry->caller = caller;
+	),
+	TP_printk("dev %d:%d ino 0x%llx pos %lld length %lld flags %s (0x%x) ops %ps caller %pS",
+		  MAJOR(__entry->dev), MINOR(__entry->dev),
+		   __entry->ino,
+		   __entry->pos,
+		   __entry->length,
+		   __print_flags(__entry->flags, "|", IOMAP_FLAGS_STRINGS),
+		   __entry->flags,
+		   __entry->ops,
+		   (void *)__entry->caller)
+);
+
 #endif /* _IOMAP_TRACE_H */
 
 #undef TRACE_INCLUDE_PATH
diff --git a/include/linux/iomap.h b/include/linux/iomap.h
index f9c36df6a3061b..a9f3f736017989 100644
--- a/include/linux/iomap.h
+++ b/include/linux/iomap.h
@@ -143,6 +143,62 @@ struct iomap_ops {
 			ssize_t written, unsigned flags, struct iomap *iomap);
 };
 
+/**
+ * struct iomap_iter - Iterate through a range of a file
+ * @inode: Set at the start of the iteration and should not change.
+ * @pos: The current file position we are operating on.  It is updated by
+ *	calls to iomap_iter().  Treat as read-only in the body.
+ * @len: The remaining length of the file segment we're operating on.
+ *	It is updated at the same time as @pos.
+ * @processed: The number of bytes processed by the body in the most recent
+ *	iteration, or a negative errno. 0 causes the iteration to stop.
+ * @flags: Zero or more of the iomap_begin flags above.
+ * @iomap: Map describing the I/O iteration
+ * @srcmap: Source map for COW operations
+ */
+struct iomap_iter {
+	struct inode *inode;
+	loff_t pos;
+	u64 len;
+	ssize_t processed;
+	unsigned flags;
+	struct iomap iomap;
+	struct iomap srcmap;
+};
+
+int iomap_iter(struct iomap_iter *iter, const struct iomap_ops *ops);
+
+/**
+ * iomap_length - length of the current iomap iteration
+ * @iter: iteration structure
+ *
+ * Returns the length that the operation applies to for the current iteration.
+ */
+static inline u64 iomap_length(const struct iomap_iter *iter)
+{
+	u64 end = iter->iomap.offset + iter->iomap.length;
+
+	if (iter->srcmap.type != IOMAP_HOLE)
+		end = min(end, iter->srcmap.offset + iter->srcmap.length);
+	return min(iter->len, end - iter->pos);
+}
+
+/**
+ * iomap_iter_srcmap - return the source map for the current iomap iteration
+ * @i: iteration structure
+ *
+ * Write operations on file systems with reflink support might require a
+ * source and a destination map.  This function retourns the source map
+ * for a given operation, which may or may no be identical to the destination
+ * map in &i->iomap.
+ */
+static inline struct iomap *iomap_iter_srcmap(struct iomap_iter *i)
+{
+	if (i->srcmap.type != IOMAP_HOLE)
+		return &i->srcmap;
+	return &i->iomap;
+}
+
 /*
  * Main iomap iterator function.
  */
-- 
2.30.2


  parent reply	other threads:[~2021-07-19 10:46 UTC|newest]

Thread overview: 59+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-19 10:34 RFC: switch iomap to an iterator model Christoph Hellwig
2021-07-19 10:34 ` [PATCH 01/27] iomap: fix a trivial comment typo in trace.h Christoph Hellwig
2021-07-19 16:00   ` Darrick J. Wong
2021-07-19 10:34 ` [PATCH 02/27] iomap: remove the iomap arguments to ->page_{prepare,done} Christoph Hellwig
2021-07-19 16:04   ` Darrick J. Wong
2021-07-19 10:34 ` [PATCH 03/27] iomap: mark the iomap argument to iomap_sector const Christoph Hellwig
2021-07-19 16:08   ` Darrick J. Wong
2021-07-20  9:52     ` Nikolay Borisov
2021-07-26  8:12     ` Christoph Hellwig
2021-07-19 10:34 ` [PATCH 04/27] fs: mark the iomap argument to __block_write_begin_int const Christoph Hellwig
2021-07-19 17:35   ` Darrick J. Wong
2021-07-19 10:34 ` [PATCH 05/27] fsdax: mark the iomap argument to dax_iomap_sector as const Christoph Hellwig
2021-07-19 17:35   ` Darrick J. Wong
2021-07-19 10:34 ` [PATCH 06/27] iomap: mark the iomap argument to iomap_read_inline_data const Christoph Hellwig
2021-07-19 17:35   ` Darrick J. Wong
2021-07-19 10:35 ` [PATCH 07/27] iomap: mark the iomap argument to iomap_read_page_sync const Christoph Hellwig
2021-07-19 17:35   ` Darrick J. Wong
2021-07-19 10:35 ` Christoph Hellwig [this message]
2021-07-19 16:56   ` [PATCH 08/27] iomap: add the new iomap_iter model Darrick J. Wong
2021-07-26  8:15     ` Christoph Hellwig
2021-07-19 21:48   ` Dave Chinner
2021-07-26  8:17     ` Christoph Hellwig
2021-07-19 10:35 ` [PATCH 09/27] iomap: switch readahead and readpage to use iomap_iter Christoph Hellwig
2021-07-19 10:35 ` [PATCH 10/27] iomap: switch iomap_file_buffered_write " Christoph Hellwig
2021-07-19 10:35 ` [PATCH 11/27] iomap: switch iomap_file_unshare " Christoph Hellwig
2021-07-19 10:35 ` [PATCH 12/27] iomap: switch iomap_zero_range " Christoph Hellwig
2021-07-19 10:35 ` [PATCH 13/27] iomap: switch iomap_page_mkwrite " Christoph Hellwig
2021-07-19 10:35 ` [PATCH 14/27] iomap: switch __iomap_dio_rw " Christoph Hellwig
2021-07-19 10:35 ` [PATCH 15/27] iomap: switch iomap_fiemap " Christoph Hellwig
2021-07-19 10:35 ` [PATCH 16/27] iomap: switch iomap_bmap " Christoph Hellwig
2021-07-19 17:05   ` Darrick J. Wong
2021-07-26  8:19     ` Christoph Hellwig
2021-07-26 16:39       ` Darrick J. Wong
2021-07-27  6:31         ` Christoph Hellwig
2021-07-27 14:32           ` Darrick J. Wong
2021-07-19 10:35 ` [PATCH 17/27] iomap: switch iomap_seek_hole " Christoph Hellwig
2021-07-19 17:22   ` Darrick J. Wong
2021-07-26  8:22     ` Christoph Hellwig
2021-07-26 16:41       ` Darrick J. Wong
2021-07-19 10:35 ` [PATCH 18/27] iomap: switch iomap_seek_data " Christoph Hellwig
2021-07-19 10:35 ` [PATCH 19/27] iomap: switch iomap_swapfile_activate " Christoph Hellwig
2021-07-19 10:35 ` [PATCH 20/27] fsdax: switch dax_iomap_rw " Christoph Hellwig
2021-07-19 22:10   ` Dave Chinner
2021-07-26  8:25     ` Christoph Hellwig
2021-07-19 10:35 ` [PATCH 21/27] iomap: remove iomap_apply Christoph Hellwig
2021-07-19 17:48   ` Darrick J. Wong
2021-07-19 10:35 ` [PATCH 22/27] iomap: pass an iomap_iter to various buffered I/O helpers Christoph Hellwig
2021-07-19 17:48   ` Darrick J. Wong
2021-07-19 10:35 ` [PATCH 23/27] iomap: rework unshare flag Christoph Hellwig
2021-07-19 17:44   ` Darrick J. Wong
2021-07-19 10:35 ` [PATCH 24/27] fsdax: factor out helpers to simplify the dax fault code Christoph Hellwig
2021-07-19 10:35 ` [PATCH 25/27] fsdax: factor out a dax_fault_actor() helper Christoph Hellwig
2021-07-19 10:35 ` [PATCH 26/27] fsdax: switch the fault handlers to use iomap_iter Christoph Hellwig
2021-07-19 17:35   ` Darrick J. Wong
2021-07-19 10:35 ` [PATCH 27/27] iomap: constify iomap_iter_srcmap Christoph Hellwig
2021-07-19 17:44   ` Darrick J. Wong
2021-07-19 17:57 ` RFC: switch iomap to an iterator model Darrick J. Wong
2021-07-27  8:07   ` DAX setup pains, was " Christoph Hellwig
2021-07-29 20:33 ` Darrick J. Wong

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