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Revision 4860abb91f3d7fbaf8147d54782149bb1fc45892 authored by Steve French on 06 February 2024, 22:34:22 UTC, committed by Steve French on 16 February 2024, 04:19:23 UTC 
smb: Fix regression in writes when non-standard maximum write size negotiated
 
The conversion to netfs in the 6.3 kernel caused a regression when
maximum write size is set by the server to an unexpected value which is
not a multiple of 4096 (similarly if the user overrides the maximum
write size by setting mount parm "wsize", but sets it to a value that
is not a multiple of 4096).  When negotiated write size is not a
multiple of 4096 the netfs code can skip the end of the final
page when doing large sequential writes, causing data corruption.

This section of code is being rewritten/removed due to a large
netfs change, but until that point (ie for the 6.3 kernel until now)
we can not support non-standard maximum write sizes.

Add a warning if a user specifies a wsize on mount that is not
a multiple of 4096 (and round down), also add a change where we
round down the maximum write size if the server negotiates a value
that is not a multiple of 4096 (we also have to check to make sure that
we do not round it down to zero).

Reported-by: R. Diez" <rdiez-2006@rd10.de>
Fixes: d08089f649a0 ("cifs: Change the I/O paths to use an iterator rather than a page list")
Suggested-by: Ronnie Sahlberg <ronniesahlberg@gmail.com>
Acked-by: Ronnie Sahlberg <ronniesahlberg@gmail.com>
Tested-by: Matthew Ruffell <matthew.ruffell@canonical.com>
Reviewed-by: Shyam Prasad N <sprasad@microsoft.com>
Cc: stable@vger.kernel.org # v6.3+
Cc: David Howells <dhowells@redhat.com>
Signed-off-by: Steve French <stfrench@microsoft.com>
1 parent 8bde59b
Raw File
test_klp_callbacks_busy.c 
// SPDX-License-Identifier: GPL-2.0
// Copyright (C) 2018 Joe Lawrence <joe.lawrence@redhat.com>

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/workqueue.h>
#include <linux/delay.h>

/* load/run-time control from sysfs writer  */
static bool block_transition;
module_param(block_transition, bool, 0644);
MODULE_PARM_DESC(block_transition, "block_transition (default=false)");

static void busymod_work_func(struct work_struct *work);
static DECLARE_WORK(work, busymod_work_func);
static DECLARE_COMPLETION(busymod_work_started);

static void busymod_work_func(struct work_struct *work)
{
	pr_info("%s enter\n", __func__);
	complete(&busymod_work_started);

	while (READ_ONCE(block_transition)) {
		/*
		 * Busy-wait until the sysfs writer has acknowledged a
		 * blocked transition and clears the flag.
		 */
		msleep(20);
	}

	pr_info("%s exit\n", __func__);
}

static int test_klp_callbacks_busy_init(void)
{
	pr_info("%s\n", __func__);
	schedule_work(&work);

	/*
	 * To synchronize kernel messages, hold the init function from
	 * exiting until the work function's entry message has printed.
	 */
	wait_for_completion(&busymod_work_started);

	if (!block_transition) {
		/*
		 * Serialize output: print all messages from the work
		 * function before returning from init().
		 */
		flush_work(&work);
	}

	return 0;
}

static void test_klp_callbacks_busy_exit(void)
{
	WRITE_ONCE(block_transition, false);
	flush_work(&work);
	pr_info("%s\n", __func__);
}

module_init(test_klp_callbacks_busy_init);
module_exit(test_klp_callbacks_busy_exit);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Joe Lawrence <joe.lawrence@redhat.com>");
MODULE_DESCRIPTION("Livepatch test: busy target module");
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