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Date: Mon, 13 Oct 2014 19:58:53 -0700
From: "Darrick J. Wong" <darrick.wong@...cle.com>
To: tytso@....edu
Cc: linux-ext4@...r.kernel.org
Subject: Re: [PATCH 15/34] libext2fs: support BLKZEROOUT/FALLOC_FL_ZERO_RANGE
in ext2fs_zero_blocks
On Sat, Sep 13, 2014 at 03:12:53PM -0700, Darrick J. Wong wrote:
> 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 when possible.
>
> Signed-off-by: Darrick J. Wong <darrick.wong@...cle.com>
> ---
> contrib/fallocate.c | 14 +++++++++
> lib/ext2fs/ext2_io.h | 7 ++++-
> lib/ext2fs/io_manager.c | 11 +++++++
> lib/ext2fs/mkjournal.c | 6 ++++
> lib/ext2fs/test_io.c | 21 ++++++++++++++
> lib/ext2fs/unix_io.c | 71 +++++++++++++++++++++++++++++++++++++++++++++++
> 6 files changed, 128 insertions(+), 2 deletions(-)
>
>
> diff --git a/contrib/fallocate.c b/contrib/fallocate.c
> index 1f9b59a..01d4af7 100644
> --- a/contrib/fallocate.c
> +++ b/contrib/fallocate.c
> @@ -36,6 +36,8 @@
> // #include <linux/falloc.h>
> #define FALLOC_FL_KEEP_SIZE 0x01
> #define FALLOC_FL_PUNCH_HOLE 0x02 /* de-allocates range */
> +#define FALLOC_FL_COLLAPSE_RANGE 0x08
> +#define FALLOC_FL_ZERO_RANGE 0x10
>
> void usage(void)
> {
> @@ -95,7 +97,7 @@ int main(int argc, char **argv)
> int error;
> int tflag = 0;
>
> - while ((opt = getopt(argc, argv, "npl:o:t")) != -1) {
> + while ((opt = getopt(argc, argv, "npl:o:tzc")) != -1) {
> switch(opt) {
> case 'n':
> /* do not change filesize */
> @@ -106,6 +108,16 @@ int main(int argc, char **argv)
> falloc_mode = (FALLOC_FL_PUNCH_HOLE |
> FALLOC_FL_KEEP_SIZE);
> break;
> + case 'c':
> + /* collapse range mode */
> + falloc_mode = (FALLOC_FL_COLLAPSE_RANGE |
> + FALLOC_FL_KEEP_SIZE);
> + break;
> + case 'z':
> + /* zero range mode */
> + falloc_mode = (FALLOC_FL_ZERO_RANGE |
> + FALLOC_FL_KEEP_SIZE);
> + break;
> case 'l':
> length = cvtnum(optarg);
> break;
> diff --git a/lib/ext2fs/ext2_io.h b/lib/ext2fs/ext2_io.h
> index 4c5a5c5..1faa720 100644
> --- a/lib/ext2fs/ext2_io.h
> +++ b/lib/ext2fs/ext2_io.h
> @@ -93,7 +93,9 @@ struct struct_io_manager {
> errcode_t (*cache_readahead)(io_channel channel,
> unsigned long long block,
> unsigned long long count);
> - long reserved[15];
> + errcode_t (*zeroout)(io_channel channel, unsigned long long block,
> + unsigned long long count);
> + long reserved[14];
> };
>
> #define IO_FLAG_RW 0x0001
> @@ -125,6 +127,9 @@ 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);
> extern errcode_t io_channel_cache_readahead(io_channel io,
> diff --git a/lib/ext2fs/io_manager.c b/lib/ext2fs/io_manager.c
> index dc5888d..c395d61 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 6f3a862..5be425c 100644
> --- a/lib/ext2fs/mkjournal.c
> +++ b/lib/ext2fs/mkjournal.c
> @@ -164,6 +164,12 @@ 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/test_io.c b/lib/ext2fs/test_io.c
> index b03a939..f7c50d1 100644
> --- a/lib/ext2fs/test_io.c
> +++ b/lib/ext2fs/test_io.c
> @@ -86,6 +86,7 @@ void (*test_io_cb_write_byte)
> #define TEST_FLAG_SET_OPTION 0x20
> #define TEST_FLAG_DISCARD 0x40
> #define TEST_FLAG_READAHEAD 0x80
> +#define TEST_FLAG_ZEROOUT 0x100
>
> static void test_dump_block(io_channel channel,
> struct test_private_data *data,
> @@ -507,6 +508,25 @@ static errcode_t test_cache_readahead(io_channel channel,
> return retval;
> }
>
> +static errcode_t test_zeroout(io_channel channel, unsigned long long block,
> + unsigned long long count)
> +{
> + struct test_private_data *data;
> + errcode_t retval = 0;
> +
> + EXT2_CHECK_MAGIC(channel, EXT2_ET_MAGIC_IO_CHANNEL);
> + data = (struct test_private_data *) channel->private_data;
> + EXT2_CHECK_MAGIC(data, EXT2_ET_MAGIC_TEST_IO_CHANNEL);
> +
> + if (data->real)
> + retval = io_channel_zeroout(data->real, block, count);
> + if (data->flags & TEST_FLAG_ZEROOUT)
> + fprintf(data->outfile,
> + "Test_io: zeroout(%llu, %llu) returned %s\n",
> + block, count, retval ? error_message(retval) : "OK");
> + return retval;
> +}
> +
> static struct struct_io_manager struct_test_manager = {
> .magic = EXT2_ET_MAGIC_IO_MANAGER,
> .name = "Test I/O Manager",
> @@ -523,6 +543,7 @@ static struct struct_io_manager struct_test_manager = {
> .write_blk64 = test_write_blk64,
> .discard = test_discard,
> .cache_readahead = test_cache_readahead,
> + .zeroout = test_zeroout,
> };
>
> io_manager test_io_manager = &struct_test_manager;
> diff --git a/lib/ext2fs/unix_io.c b/lib/ext2fs/unix_io.c
> index 189adce..20e5b64 100644
> --- a/lib/ext2fs/unix_io.c
> +++ b/lib/ext2fs/unix_io.c
> @@ -986,6 +986,76 @@ 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 (getenv("UNIX_IO_NOZEROOUT"))
> + goto unimplemented;
> +
> + 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);
NAK this line for now. I think I've uncovered a race condition where
pwrite+blkzeroout+pread returns the pwritten contents instead of zeroes as I
was expecting.
--D
> +#else
> + goto unimplemented;
> +#endif
> + } else {
> +#if defined(HAVE_FALLOCATE) && defined(FALLOC_FL_ZERO_RANGE)
> + int flag = FALLOC_FL_ZERO_RANGE;
> + struct stat statbuf;
> +
> + /*
> + * If we're trying to zero a range past the end of the file,
> + * just use regular fallocate to get there, because zeroing
> + * a range past EOF does not extend the file.
> + */
> + ret = fstat(data->dev, &statbuf);
> + if (ret)
> + goto err;
> + if (statbuf.st_size < (block + count) * channel->block_size)
> + flag = 0;
> + /*
> + * If we are not on block device, try to use the zero out
> + * primitive.
> + */
> + ret = fallocate(data->dev,
> + flag,
> + (off_t)(block) * channel->block_size,
> + (off_t)(count) * channel->block_size);
> +#else
> + goto unimplemented;
> +#endif
> + }
> +err:
> + 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 = {
> .magic = EXT2_ET_MAGIC_IO_MANAGER,
> .name = "Unix I/O Manager",
> @@ -1002,6 +1072,7 @@ static struct struct_io_manager struct_unix_manager = {
> .write_blk64 = unix_write_blk64,
> .discard = unix_discard,
> .cache_readahead = unix_cache_readahead,
> + .zeroout = unix_zeroout,
> };
>
> io_manager unix_io_manager = &struct_unix_manager;
>
> --
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