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Subject: Re: Regression: hibernation is broken since
 e6bc9de714972cac34daa1dc1567ee48a47a9342
To:     "Darrick J. Wong" <darrick.wong@oracle.com>,
        Christoph Hellwig <hch@lst.de>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        linux-pm@vger.kernel.org
References: <20200213172351.GA6747@dumbo> <20200213175753.GS6874@magnolia>
 <20200213183515.GA8798@dumbo> <20200213193410.GB6868@magnolia>
 <20200213194135.GF6870@magnolia> <20200214211523.GA32637@dumbo>
 <20200222002319.GK9504@magnolia> <20200223190311.GA26811@dumbo>
 <20200225202632.GE6748@magnolia>
From:   Brad Campbell <brad@fnarfbargle.com>
Message-ID: <f9fe045d-3613-7443-f634-f17e5630ded3@fnarfbargle.com>
Date:   Tue, 17 Mar 2020 23:51:58 +0800
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On 26/2/20 4:26 am, Darrick J. Wong wrote:
> On Sun, Feb 23, 2020 at 08:03:11PM +0100, Domenico Andreoli wrote:
>> On Fri, Feb 21, 2020 at 04:23:19PM -0800, Darrick J. Wong wrote:
>>>
>>> Ok, third try.  Does the following work?  This is a little more
>>> selective in that it only disables the write protection on the swap
>>> device/file that uswusp is going to write to.
>>
>> Yes it works but also verified that once the S_SWAPFILE bit is cleared
>> it's never restored, therefore the protecton is gone after the first
>> hibernation.
> 
> Ok, good.  Now can you try the third part, which ought to re-apply
> S_SWAPFILE after a successful resume, please?  Assuming this works, I
> think we're ready with a fixpatch.
> 

I just bumped up against it upgrading from 5.2 to 5.5 & a long bisection results in apparently the same point :
# first bad commit: [dc617f29dbe5ef0c8ced65ce62c464af1daaab3d] vfs: don't allow writes to swap files

Tested-By: Brad Campbell <lists2009@fnarfbargle.com>

> --D
> 
> diff --git a/include/linux/swap.h b/include/linux/swap.h
> index 1e99f7ac1d7e..add93e205850 100644
> --- a/include/linux/swap.h
> +++ b/include/linux/swap.h
> @@ -458,6 +458,7 @@ extern void swap_free(swp_entry_t);
>   extern void swapcache_free_entries(swp_entry_t *entries, int n);
>   extern int free_swap_and_cache(swp_entry_t);
>   extern int swap_type_of(dev_t, sector_t, struct block_device **);
> +extern void swap_relockall(void);
>   extern unsigned int count_swap_pages(int, int);
>   extern sector_t map_swap_page(struct page *, struct block_device **);
>   extern sector_t swapdev_block(int, pgoff_t);
> diff --git a/kernel/power/user.c b/kernel/power/user.c
> index 77438954cc2b..b11f7037ce5e 100644
> --- a/kernel/power/user.c
> +++ b/kernel/power/user.c
> @@ -271,6 +271,8 @@ static long snapshot_ioctl(struct file *filp, unsigned int cmd,
>   			break;
>   		}
>   		error = hibernation_restore(data->platform_support);
> +		if (!error)
> +			swap_relockall();
>   		break;
>   
>   	case SNAPSHOT_FREE:
> @@ -372,10 +374,17 @@ static long snapshot_ioctl(struct file *filp, unsigned int cmd,
>   			 */
>   			swdev = new_decode_dev(swap_area.dev);
>   			if (swdev) {
> +				struct block_device *bd;
> +
>   				offset = swap_area.offset;
> -				data->swap = swap_type_of(swdev, offset, NULL);
> +				data->swap = swap_type_of(swdev, offset, &bd);
>   				if (data->swap < 0)
>   					error = -ENODEV;
> +
> +				inode_lock(bd->bd_inode);
> +				bd->bd_inode->i_flags &= ~S_SWAPFILE;
> +				inode_unlock(bd->bd_inode);
> +				bdput(bd);
>   			} else {
>   				data->swap = -1;
>   				error = -EINVAL;
> diff --git a/mm/swapfile.c b/mm/swapfile.c
> index b2a2e45c9a36..a64dcba10db6 100644
> --- a/mm/swapfile.c
> +++ b/mm/swapfile.c
> @@ -1799,6 +1799,32 @@ int swap_type_of(dev_t device, sector_t offset, struct block_device **bdev_p)
>   	return -ENODEV;
>   }
>   
> +/* Re-lock swap devices after resuming from userspace suspend. */
> +void swap_relockall(void)
> +{
> +	int type;
> +
> +	spin_lock(&swap_lock);
> +	for (type = 0; type < nr_swapfiles; type++) {
> +		struct swap_info_struct *sis = swap_info[type];
> +		struct block_device *bdev = bdgrab(sis->bdev);
> +
> +		/*
> +		 * uswsusp only knows how to suspend to block devices, so we
> +		 * can skip swap files.
> +		 */
> +		if (!(sis->flags & SWP_WRITEOK) ||
> +		    !(sis->flags & SWP_BLKDEV))
> +			continue;
> +
> +		inode_lock(bd->bd_inode);
> +		bd->bd_inode->i_flags |= S_SWAPFILE;
> +		inode_unlock(bd->bd_inode);
> +		bdput(bd);
> +	}
> +	spin_unlock(&swap_lock);
> +}
> +
>   /*
>    * Get the (PAGE_SIZE) block corresponding to given offset on the swapdev
>    * corresponding to given index in swap_info (swap type).
>