[Ocfs2-tools-devel] [PATCH] o2image: Autodetect pipes and use proper FILENO defines. v2

[Sunil Mushran]

Signed-off-by: Sunil Mushran<sunil.mushran at oracle.com>


On 06/11/2010 03:57 PM, Joel Becker wrote:
> [Take two - forgot to reset fpos when lseek fails]
>
> First off, don't use a naked '1' where we mean STDOUT_FILENO.  Fixed.
>
> Secondly, detect whether our file descriptor is a stream with lseek().
> That way we can eventually do our own compression if we want, and the
> write code won't care.
>
> With a write function that detects where we're writing, we can do our
> zeroing in hunks of 1MB.  Might be faster.
>
> Signed-off-by: Joel Becker<joel.becker at oracle.com>
> ---
>   o2image/o2image.c |  135 ++++++++++++++++++++++++++++++++++++++++------------
>   1 files changed, 104 insertions(+), 31 deletions(-)
>
> diff --git a/o2image/o2image.c b/o2image/o2image.c
> index 891ec3a..215503c 100644
> --- a/o2image/o2image.c
> +++ b/o2image/o2image.c
> @@ -405,10 +405,98 @@ out:
>   	return ret;
>   }
>
> +/*
> + * This write function takes a file descriptor and pretends to be
> + * pwrite64().  If the descriptor is seekable, it will just call
> + * pwrite64().  Otherwise it will send zeros down to fill any holes.  The
> + * caller can't go backwards in the file, because seeking may not be
> + * possible.
> + *
> + * It returns -1 if it fails to finish up at offset+count.  It will
> + * print its error, so the caller does not need to.
> + */
> +#define ZERO_BUF_SIZE  (1<<20)
> +static ssize_t raw_write(ocfs2_filesys *fs, int fd, const void *buf,
> +			 size_t count, loff_t offset)
> +{
> +	errcode_t ret;
> +	ssize_t written;
> +	static char *zero_buf = NULL;
> +	static int can_seek = -1;
> +	static loff_t fpos = 0;
> +	loff_t to_write;
> +
> +	if (can_seek == -1) {
> +		/* Test if we can seek/pwrite */
> +		fpos = lseek64(fd, 0, SEEK_CUR);
> +		if (fpos<  0) {
> +			fpos = 0;
> +			can_seek = 0;
> +		} else
> +			can_seek = 1;
> +	}
> +
> +	if (!can_seek&&  !zero_buf) {
> +		ret = ocfs2_malloc_blocks(fs->fs_io,
> +					  ZERO_BUF_SIZE / fs->fs_blocksize,
> +					&zero_buf);
> +		if (ret) {
> +			com_err(program_name, ret,
> +				"while allocating zero buffer");
> +			written = -1;
> +			goto out;
> +		}
> +		memset(zero_buf, 0, ZERO_BUF_SIZE);
> +	}
> +
> +	if (can_seek) {
> +		written = pwrite64(fd, buf, count, offset);
> +		goto out;
> +	}
> +
> +	/* Ok, let's fake pwrite64() for the caller */
> +	if (fpos>  offset) {
> +		com_err(program_name, OCFS2_ET_INTERNAL_FAILURE,
> +			": file position went backwards while writing "
> +			"image file");
> +		written = -1;
> +		goto out;
> +	}
> +
> +	while (fpos<  offset) {
> +		to_write = ocfs2_min((loff_t)ZERO_BUF_SIZE, offset - fpos);
> +		written = write(fd, zero_buf, to_write);
> +		if (written<  0) {
> +			com_err(program_name, OCFS2_ET_IO,
> +				"while writing zero blocks: %s",
> +				strerror(errno));
> +			goto out;
> +		}
> +		fpos += written;
> +	}
> +
> +	to_write = count;
> +	while (to_write) {
> +		written = write(fd, buf, to_write);
> +		if (written<  0) {
> +			com_err(program_name, OCFS2_ET_IO,
> +				"while writing data blocks: %s",
> +				strerror(errno));
> +			goto out;
> +		}
> +		fpos += written;
> +		to_write -= written;
> +	}
> +	/* Ok, we did it */
> +	written = count;
> +
> +out:
> +	return written;
> +}
> +
>   static errcode_t write_raw_image_file(ocfs2_filesys *ofs, int fd)
>   {
>   	struct ocfs2_super_block *super;
> -	char *zero_buf = NULL;
>   	char *blk_buf = NULL;
>   	uint64_t blk = -1;
>   	ssize_t count;
> @@ -417,47 +505,32 @@ static errcode_t write_raw_image_file(ocfs2_filesys *ofs, int fd)
>   	super = OCFS2_RAW_SB(ofs->fs_super);
>   	ret = ocfs2_malloc_block(ofs->fs_io,&blk_buf);
>   	if (ret) {
> -		com_err(program_name, ret, "error while allocating buffer ");
> -		goto out;
> -	}
> -
> -	ret = ocfs2_malloc_block(ofs->fs_io,&zero_buf);
> -	if (ret) {
> -		com_err(program_name, ret, "error while allocating buffer ");
> +		com_err(program_name, ret, "while allocating I/O buffer");
>   		goto out;
>   	}
> -	memset(zero_buf, 0, ofs->fs_blocksize);
>
>   	while (++blk<  ofs->fs_blocks) {
>   		if (ocfs2_image_test_bit(ofs, blk)) {
>   			ret = ocfs2_read_blocks(ofs, blk, 1, blk_buf);
>   			if (ret) {
> -				com_err(program_name, ret, "error occurred "
> -					"during read cluster %"PRIu64"", blk);
> -				goto out;
> +				com_err(program_name, ret,
> +					"while reading block %"PRIu64, blk);
> +				break;
>   			}
>
> -			if (fd == 1)
> -				count = write(fd, blk_buf, ofs->fs_blocksize);
> -			else
> -				count = pwrite64(fd, blk_buf, ofs->fs_blocksize,
> -					(__off64_t)(blk * ofs->fs_blocksize));
> -		} else if (fd == 1) {
> -			count = write(fd, zero_buf, ofs->fs_blocksize);
> -		} else
> -			continue;
> -
> -		if ((count == -1) || (count<  ofs->fs_blocksize)) {
> -			com_err(program_name, errno, "error writing "
> -				"blk %"PRIu64"", blk);
> -			goto out;
> +			count = raw_write(ofs, fd, blk_buf,
> +					  ofs->fs_blocksize,
> +					  (loff_t)(blk * ofs->fs_blocksize));
> +			if (count<  0) {
> +				ret = OCFS2_ET_IO;
> +				break;
> +			}
>   		}
>   	}
> +
>   out:
>   	if (blk_buf)
>   		ocfs2_free(&blk_buf);
> -	if (zero_buf)
> -		ocfs2_free(&zero_buf);
>   	return ret;
>   }
>
> @@ -621,7 +694,7 @@ int main(int argc, char **argv)
>   	int raw_flag      	= 0;
>   	int install_flag  	= 0;
>   	int interactive		= 0;
> -	int fd            	= 1;
> +	int fd            	= STDOUT_FILENO;
>   	int c;
>
>   	if (argc&&  *argv)
> @@ -716,7 +789,7 @@ int main(int argc, char **argv)
>   	}
>
>   	if (strcmp(dest_file, "-") == 0)
> -		fd = 1;
> +		fd = STDOUT_FILENO;
>   	else {
>   		/* prompt user for image creation */
>   		if (interactive&&  !install_flag&&
> @@ -754,7 +827,7 @@ out:
>   		com_err(program_name, ret, "while closing file \"%s\"",
>   			src_file);
>
> -	if (fd&&  (fd != 1))
> +	if (fd&&  (fd != STDOUT_FILENO))
>   		close(fd);
>
>   	return ret;
>