/*
 * Helper function for splitting a string into an argv-like array.
 */

#include <linux/kernel.h>
#include <linux/ctype.h>
#include <linux/string.h>
#include <linux/slab.h>
#include <linux/export.h>

static int count_argc(const char *str)
{
	int count = 0;
	bool was_space;

	for (was_space = true; *str; str++) {
		if (isspace(*str)) {
			was_space = true;
		} else if (was_space) {
			was_space = false;
			count++;
		}
	}

	return count;
}

/**
 * argv_free - free an argv
 * @argv - the argument vector to be freed
 *
 * Frees an argv and the strings it points to.
 */
void argv_free(char **argv)
{
	argv--;
	kfree(argv[0]);
	kfree(argv);
}
EXPORT_SYMBOL(argv_free);

/**
 * argv_split - split a string at whitespace, returning an argv
 * @gfp: the GFP mask used to allocate memory
 * @str: the string to be split
 * @argcp: returned argument count
 *
 * Returns an array of pointers to strings which are split out from
 * @str.  This is performed by strictly splitting on white-space; no
 * quote processing is performed.  Multiple whitespace characters are
 * considered to be a single argument separator.  The returned array
 * is always NULL-terminated.  Returns NULL on memory allocation
 * failure.
 *
 * The source string at `str' may be undergoing concurrent alteration via
 * userspace sysctl activity (at least).  The argv_split() implementation
 * attempts to handle this gracefully by taking a local copy to work on.
 */
char **argv_split(gfp_t gfp, const char *str, int *argcp)
{
	char *argv_str;
	bool was_space;
	char **argv, **argv_ret;
	int argc;

	argv_str = kstrndup(str, KMALLOC_MAX_SIZE - 1, gfp);
	if (!argv_str)
		return NULL;

	argc = count_argc(argv_str);
	argv = kmalloc(sizeof(*argv) * (argc + 2), gfp);
	if (!argv) {
		kfree(argv_str);
		return NULL;
	}

	*argv = argv_str;
	argv_ret = ++argv;
	for (was_space = true; *argv_str; argv_str++) {
		if (isspace(*argv_str)) {
			was_space = true;
			*argv_str = 0;
		} else if (was_space) {
			was_space = false;
			*argv++ = argv_str;
		}
	}
	*argv = NULL;

	if (argcp)
		*argcp = argc;
	return argv_ret;
}
EXPORT_SYMBOL(argv_split);
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<tr class='logheader'><td><span title='2017-01-31 13:28:06 -0500'>2017-01-31</span></td><td class='logsubject'><a href='/cgit.cgi/linux/net-next.git/commit/net/core/ethtool.c?id=4d1ceea8516cd6adf21f6b75995e2a7d4f376f9b'>net: ethtool: convert large order kmalloc allocations to vzalloc</a></td><td>Alexei Starovoitov</td><td>1</td><td><span class='deletions'>-17</span>/<span class='insertions'>+22</span></td></tr>
<tr class='nohover-highlight'><td/><td colspan='5' class='logmsg'>
under memory pressure 'ethtool -S' command may warn:
[ 2374.385195] ethtool: page allocation failure: order:4, mode:0x242c0c0
[ 2374.405573] CPU: 12 PID: 40211 Comm: ethtool Not tainted
[ 2374.423071] Call Trace:
[ 2374.423076]  [&lt;ffffffff8148cb29&gt;] dump_stack+0x4d/0x64
[ 2374.423080]  [&lt;ffffffff811667cb&gt;] warn_alloc_failed+0xeb/0x150
[ 2374.423082]  [&lt;ffffffff81169cd3&gt;] ? __alloc_pages_direct_compact+0x43/0xf0
[ 2374.423084]  [&lt;ffffffff8116a25c&gt;] __alloc_pages_nodemask+0x4dc/0xbf0
[ 2374.423091]  [&lt;ffffffffa0023dc2&gt;] ? cmd_exec+0x722/0xcd0 [mlx5_core]
[ 2374.423095]  [&lt;ffffffff811b3dcc&gt;] alloc_pages_current+0x8c/0x110
[ 2374.423097]  [&lt;ffffffff81168859&gt;] alloc_kmem_pages+0x19/0x90
[ 2374.423099]  [&lt;ffffffff81186e5e&gt;] kmalloc_order_trace+0x2e/0xe0
[ 2374.423101]  [&lt;ffffffff811c0084&gt;] __kmalloc+0x204/0x220
[ 2374.423105]  [&lt;ffffffff816c269e&gt;] dev_ethtool+0xe4e/0x1f80
[ 2374.423106]  [&lt;ffffffff816b967e&gt;] ? dev_get_by_name_rcu+0x5e/0x80
[ 2374.423108]  [&lt;ffffffff816d6926&gt;] dev_ioctl+0x156/0x560
[ 2374.423111]  [&lt;ffffffff811d4c68&gt;] ? mem_cgroup_commit_charge+0x78/0x3c0
[ 2374.423117]  [&lt;ffffffff8169d542&gt;] sock_do_ioctl+0x42/0x50
[ 2374.423119]  [&lt;ffffffff8169d9c3&gt;] sock_ioctl+0x1b3/0x250
[ 2374.423121]  [&lt;ffffffff811f0f42&gt;] do_vfs_ioctl+0x92/0x580
[ 2374.423123]  [&lt;ffffffff8100222b&gt;] ? do_audit_syscall_entry+0x4b/0x70
[ 2374.423124]  [&lt;ffffffff8100287c&gt;] ? syscall_trace_enter_phase1+0xfc/0x120
[ 2374.423126]  [&lt;ffffffff811f14a9&gt;] SyS_ioctl+0x79/0x90
[ 2374.423127]  [&lt;ffffffff81002bb0&gt;] do_syscall_64+0x50/0xa0
[ 2374.423129]  [&lt;ffffffff817e19bc&gt;] entry_SYSCALL64_slow_path+0x25/0x25

~1160 mlx5 counters ~= order 4 allocation which is unlikely to succeed
under memory pressure. Convert them to vzalloc() as ethtool_get_regs() does.
Also take care of drivers without counters similar to
commit 67ae7cf1eeda ("ethtool: Allow zero-length register dumps again")
and reduce warn_on to warn_on_once.

Signed-off-by: Alexei Starovoitov &lt;ast@kernel.org&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;


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