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Message-ID: <20140508001337.GC8923@birch.djwong.org>
Date:	Wed, 7 May 2014 17:13:37 -0700
From:	"Darrick J. Wong" <darrick.wong@...cle.com>
To:	Lukáš Czerner <lczerner@...hat.com>
Cc:	tytso@....edu, linux-ext4@...r.kernel.org
Subject: [PATCH 1/2] libext2fs: support BLKZEROOUT/FALLOC_FL_ZERO_RANGE in
 ext2fs_zero_blocks

Here's the first part, which teaches the IO manager how to connect with the
zero out ioctls.

--D
---
Plumb a new call into the IO manager to support translating
ext2fs_zero_blocks calls into the equivalent kernel-level BLKZEROOUT
ioctl or FALLOC_FL_ZERO_RANGE fallocate flag primitives.

Signed-off-by: Darrick J. Wong <darrick.wong@...cle.com>
---
 lib/ext2fs/ext2_io.h    |    7 +++++-
 lib/ext2fs/io_manager.c |   11 ++++++++++
 lib/ext2fs/mkjournal.c  |    6 +++++
 lib/ext2fs/unix_io.c    |   54 +++++++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 77 insertions(+), 1 deletion(-)

diff --git a/lib/ext2fs/ext2_io.h b/lib/ext2fs/ext2_io.h
index 1894fb8..98d56aa 100644
--- a/lib/ext2fs/ext2_io.h
+++ b/lib/ext2fs/ext2_io.h
@@ -90,7 +90,9 @@ struct struct_io_manager {
 					int count, const void *data);
 	errcode_t (*discard)(io_channel channel, unsigned long long block,
 			     unsigned long long count);
-	long	reserved[16];
+	errcode_t (*zeroout)(io_channel channel, unsigned long long block,
+			     unsigned long long count);
+	long	reserved[15];
 };
 
 #define IO_FLAG_RW		0x0001
@@ -122,6 +124,9 @@ extern errcode_t io_channel_write_blk64(io_channel channel,
 extern errcode_t io_channel_discard(io_channel channel,
 				    unsigned long long block,
 				    unsigned long long count);
+extern errcode_t io_channel_zeroout(io_channel channel,
+				    unsigned long long block,
+				    unsigned long long count);
 extern errcode_t io_channel_alloc_buf(io_channel channel,
 				      int count, void *ptr);
 
diff --git a/lib/ext2fs/io_manager.c b/lib/ext2fs/io_manager.c
index 34e4859..569d16a 100644
--- a/lib/ext2fs/io_manager.c
+++ b/lib/ext2fs/io_manager.c
@@ -112,6 +112,17 @@ errcode_t io_channel_discard(io_channel channel, unsigned long long block,
 	return EXT2_ET_UNIMPLEMENTED;
 }
 
+errcode_t io_channel_zeroout(io_channel channel, unsigned long long block,
+			     unsigned long long count)
+{
+	EXT2_CHECK_MAGIC(channel, EXT2_ET_MAGIC_IO_CHANNEL);
+
+	if (channel->manager->zeroout)
+		return (channel->manager->zeroout)(channel, block, count);
+
+	return EXT2_ET_UNIMPLEMENTED;
+}
+
 errcode_t io_channel_alloc_buf(io_channel io, int count, void *ptr)
 {
 	size_t	size;
diff --git a/lib/ext2fs/mkjournal.c b/lib/ext2fs/mkjournal.c
index 884d9c0..339c7e1 100644
--- a/lib/ext2fs/mkjournal.c
+++ b/lib/ext2fs/mkjournal.c
@@ -167,6 +167,12 @@ errcode_t ext2fs_zero_blocks2(ext2_filsys fs, blk64_t blk, int num,
 		}
 		return 0;
 	}
+
+	/* Try a zero out command, if supported */
+	retval = io_channel_zeroout(fs->io, blk, num);
+	if (retval == 0)
+		return 0;
+
 	/* Allocate the zeroizing buffer if necessary */
 	if (!buf) {
 		buf = malloc(fs->blocksize * STRIDE_LENGTH);
diff --git a/lib/ext2fs/unix_io.c b/lib/ext2fs/unix_io.c
index c3185b6..d070cb0 100644
--- a/lib/ext2fs/unix_io.c
+++ b/lib/ext2fs/unix_io.c
@@ -922,6 +922,59 @@ unimplemented:
 	return EXT2_ET_UNIMPLEMENTED;
 }
 
+#if defined(__linux__) && !defined(BLKZEROOUT)
+#define BLKZEROOUT		_IO(0x12,127)
+#endif
+
+#if defined(__linux__) && !defined(FALLOC_FL_ZERO_RANGE)
+#define FALLOC_FL_ZERO_RANGE    0x10
+#endif
+
+static errcode_t unix_zeroout(io_channel channel, unsigned long long block,
+			      unsigned long long count)
+{
+	struct unix_private_data *data;
+	int		ret;
+
+	EXT2_CHECK_MAGIC(channel, EXT2_ET_MAGIC_IO_CHANNEL);
+	data = (struct unix_private_data *) channel->private_data;
+	EXT2_CHECK_MAGIC(data, EXT2_ET_MAGIC_UNIX_IO_CHANNEL);
+
+	if (channel->flags & CHANNEL_FLAGS_BLOCK_DEVICE) {
+#ifdef BLKZEROOUT
+		__u64 range[2];
+
+		range[0] = (__u64)(block) * channel->block_size;
+		range[1] = (__u64)(count) * channel->block_size;
+
+		ret = ioctl(data->dev, BLKZEROOUT, &range);
+#else
+		goto unimplemented;
+#endif
+	} else {
+#if defined(HAVE_FALLOCATE) && defined(FALLOC_FL_ZERO_RANGE)
+		/*
+		 * If we are not on block device, try to use the zero out
+		 * primitive.
+		 */
+		ret = fallocate(data->dev,
+				FALLOC_FL_ZERO_RANGE | FALLOC_FL_KEEP_SIZE,
+				(off_t)(block) * channel->block_size,
+				(off_t)(count) * channel->block_size);
+#else
+		goto unimplemented;
+#endif
+	}
+	if (ret < 0) {
+		if (errno == EOPNOTSUPP)
+			goto unimplemented;
+		return errno;
+	}
+	return 0;
+unimplemented:
+	return EXT2_ET_UNIMPLEMENTED;
+}
+
 static struct struct_io_manager struct_unix_manager = {
 	EXT2_ET_MAGIC_IO_MANAGER,
 	"Unix I/O Manager",
@@ -937,6 +990,7 @@ static struct struct_io_manager struct_unix_manager = {
 	unix_read_blk64,
 	unix_write_blk64,
 	unix_discard,
+	unix_zeroout,
 };
 
 io_manager unix_io_manager = &struct_unix_manager;
--
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