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List:       busybox
Subject:    Re: [PATCH v2] blkdiscard: new applet
From:       Ari Sundholm <ari () tuxera ! com>
Date:       2015-11-30 18:32:11
Message-ID: 1448908331.1045.26.camel () ari-lenovo
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On Mon, 2015-11-30 at 15:14 +0000, walter harms wrote:
> 
> Am 30.11.2015 15:52, schrieb Ari Sundholm:
> > From: Ari Sundholm <ari@tuxera.com>
> > 
> > This applet discards blocks on a given device.
> > Tested with multiple 32-bit and 64-bit kernel versions and two different SSDs.
> > 
> > function                                             old     new   delta
> > blkdiscard_main                                        -     300    +300
> > .rodata                                           154690  154795    +105
> > packed_usage                                       30275   30310     +35
> > applet_names                                        2499    2510     +11
> > applet_main                                         2904    2912      +8
> > applet_nameofs                                       726     728      +2
> > ------------------------------------------------------------------------------
> > (add/remove: 2/0 grow/shrink: 5/0 up/down: 461/0)             Total: 461 bytes
> > 
> > v2: Use a common error message format string when !S_ISBLK() to save space.
> > 
> > Signed-off-by: Ari Sundholm <ari@tuxera.com>
> > ---
> > util-linux/blkdiscard.c | 86 +++++++++++++++++++++++++++++++++++++++++++++++++
> > 1 file changed, 86 insertions(+)
> > create mode 100644 util-linux/blkdiscard.c
> > 
> > diff --git a/util-linux/blkdiscard.c b/util-linux/blkdiscard.c
> > new file mode 100644
> > index 0000000..2694c11
> > --- /dev/null
> > +++ b/util-linux/blkdiscard.c
> > @@ -0,0 +1,86 @@
> > +/*
> > + * Mini blkdiscard implementation for busybox
> > + *
> > + * Copyright (C) 2015 by Ari Sundholm <ari@tuxera.com> and Tuxera Inc.
> > + *
> > + * Licensed under GPLv2 or later, see file LICENSE in this source tree.
> > + */
> > +
> > +//config:config BLKDISCARD
> > +//config:	bool "blkdiscard"
> > +//config:	default y
> 
> 
> i never used/needed blkdiscard why do you set it to default y ? Is it part of any
> std. like POSIX or so ? (the man page did not mention it).
> 

Just an oversight, partly caused by the fact that the applet is useful
to myself. Indeed, most people may not need it.

blkdiscard has been part of util-linux since 2012, IIRC, but I do not
know if it is part of any standard per se.

> > +//config:	help
> > +//config:	  blkdiscard discards sectors on a given device.
> > +
> > +//kbuild:lib-$(CONFIG_BLKDISCARD) += blkdiscard.o
> > +//applet:IF_BLKDISCARD(APPLET_NOFORK(blkdiscard, blkdiscard, BB_DIR_USR_BIN, \
> > BB_SUID_DROP, blkdiscard)) +
> > +//usage:#define blkdiscard_trivial_usage
> > +//usage:       "[-o offset] [-l length] [-s] device"
> > +//usage:#define blkdiscard_full_usage "\n\n"
> > +//usage:	"Discard sectors on the given device\n"
> > +//usage:	"\n	-o offset	Byte offset into device (default: 0)"
> > +//usage:	"\n	-l length	Number of bytes to discard (default: size of device)"
> > +//usage:	"\n	-s		Perform a secure discard"
> > +//usage:
> > +//usage:#define blkdiscard_example_usage
> > +//usage:	"$ blkdiscard -o 0 -l 1G /dev/sdb"
> > +
> > +#include "libbb.h"
> > +#include <linux/fs.h>
> > +
> > +/* This is a NOFORK applet. Be very careful! */
> > +
> > +int blkdiscard_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
> > +int blkdiscard_main(int argc UNUSED_PARAM, char **argv)
> > +{
> > +	unsigned opts;
> > +	uint64_t offset = 0;
> > +	char *offset_str;
> > +	uint64_t length;
> > +	char *length_str;
> > +	struct stat st;
> > +	int fd;
> > +	uint64_t range[2];
> > +
> > +	enum {
> > +		OPT_OFFSET = (1 << 0),
> > +		OPT_LENGTH = (1 << 1),
> > +		OPT_SECURE = (1 << 2),
> > +	};
> > +
> > +	opt_complementary = "=1";
> > +	opts = getopt32(argv, "o:l:s", &offset_str, &length_str);
> > +
> > +	xstat(argv[optind], &st);
> > +	if (!S_ISBLK(st.st_mode))
> > +		bb_error_msg_and_die("%s: not a block device", argv[optind]);
> > +
> > +	fd = xopen(argv[optind], O_RDWR|O_EXCL);
> > +
> > +	if (opts & OPT_OFFSET)
> > +		offset = xatoull_sfx(offset_str, kMG_suffixes);
> > +
> > +	if (opts & OPT_LENGTH)
> > +		length = xatoull_sfx(length_str, kMG_suffixes);
> > +	else {
> > +		ioctl_or_perror_and_die(fd, BLKGETSIZE64, &length,
> > +			"Failed to get device size");
> > +		length -= offset;
> > +	}
> > +
> > +	range[0] = offset;
> > +	range[1] = length;
> 
> Can you discard offset, length ?
> 

Sure, I'll check if that shrinks the applet down a bit.

Best regards,
Ari Sundholm
ari@tuxera.com

> re,
> wh
> 
> 
> > +	ioctl_or_perror_and_die(fd,
> > +				(opts & OPT_SECURE)
> > +				? BLKSECDISCARD
> > +				: BLKDISCARD, &range,
> > +				"%s failed",
> > +				(opts & OPT_SECURE)
> > +				? "BLKSECDISCARD"
> > +				: "BLKDISCARD");
> > +
> > +	xclose(fd);
> > +
> > +	return EXIT_SUCCESS;
> > +}
> _______________________________________________
> busybox mailing list
> busybox@busybox.net
> http://lists.busybox.net/mailman/listinfo/busybox


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