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Commit a2d548db authored by Naohiro Aota's avatar Naohiro Aota Committed by Charan Teja Reddy
Browse files

mm/swapfile.c: move inode_lock out of claim_swapfile 



claim_swapfile() currently keeps the inode locked when it is successful,
or the file is already swapfile (with -EBUSY).  And, on the other error
cases, it does not lock the inode.

This inconsistency of the lock state and return value is quite confusing
and actually causing a bad unlock balance as below in the "bad_swap"
section of __do_sys_swapon().

This commit fixes this issue by moving the inode_lock() and IS_SWAPFILE
check out of claim_swapfile().  The inode is unlocked in
"bad_swap_unlock_inode" section, so that the inode is ensured to be
unlocked at "bad_swap".  Thus, error handling codes after the locking now
jumps to "bad_swap_unlock_inode" instead of "bad_swap".

    =====================================
    WARNING: bad unlock balance detected!
    5.5.0-rc7+ #176 Not tainted
    -------------------------------------
    swapon/4294 is trying to release lock (&sb->s_type->i_mutex_key) at: __do_sys_swapon+0x94b/0x3550
    but there are no more locks to release!

    other info that might help us debug this:
    no locks held by swapon/4294.

    stack backtrace:
    CPU: 5 PID: 4294 Comm: swapon Not tainted 5.5.0-rc7-BTRFS-ZNS+ #176
    Hardware name: ASUS All Series/H87-PRO, BIOS 2102 07/29/2014
    Call Trace:
     dump_stack+0xa1/0xea
     print_unlock_imbalance_bug.cold+0x114/0x123
     lock_release+0x562/0xed0
     up_write+0x2d/0x490
     __do_sys_swapon+0x94b/0x3550
     __x64_sys_swapon+0x54/0x80
     do_syscall_64+0xa4/0x4b0
     entry_SYSCALL_64_after_hwframe+0x49/0xbe
    RIP: 0033:0x7f15da0a0dc7

Change-Id: Ieaf55dfac93cfe5fe64fc6cfe7bfa502c95e2eec
Fixes: 1638045c3677 ("mm: set S_SWAPFILE on blockdev swap devices")
Signed-off-by: default avatarNaohiro Aota <naohiro.aota@wdc.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Tested-by: default avatarQais Youef <qais.yousef@arm.com>
Reviewed-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Reviewed-by: default avatarDarrick J. Wong <darrick.wong@oracle.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: <stable@vger.kernel.org>
Link: http://lkml.kernel.org/r/20200206090132.154869-1-naohiro.aota@wdc.com


Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
Git-Commit: d795a90e2ba024dbf2f22107ae89c210b98b08b8
Git-Repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git


[charante@codeaurora.org: Fix trivial merge conflicts]
Signed-off-by: default avatarCharan Teja Reddy <charante@codeaurora.org>
parent 7234d852

mm/swapfile.c

+20 −21
Original line number Original line Diff line number Diff line
@@ -2916,10 +2916,6 @@ static int claim_swapfile(struct swap_info_struct *p, struct inode *inode) 
		p->bdev = inode->i_sb->s_bdev;

		p->bdev = inode->i_sb->s_bdev;

	}

	}





	inode_lock(inode);

	if (IS_SWAPFILE(inode))

		return -EBUSY;



	return 0;

	return 0;

}

}
@@ -3174,36 +3170,41 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags) 
	mapping = swap_file->f_mapping;

	mapping = swap_file->f_mapping;

	inode = mapping->host;

	inode = mapping->host;





	/* If S_ISREG(inode->i_mode) will do inode_lock(inode); */

	error = claim_swapfile(p, inode);

	error = claim_swapfile(p, inode);

	if (unlikely(error))

	if (unlikely(error))

		goto bad_swap;

		goto bad_swap;





	inode_lock(inode);

	if (IS_SWAPFILE(inode)) {

		error = -EBUSY;

		goto bad_swap_unlock_inode;

	}



	/*

	/*

	 * Read the swap header.

	 * Read the swap header.

	 */

	 */

	if (!mapping->a_ops->readpage) {

	if (!mapping->a_ops->readpage) {

		error = -EINVAL;

		error = -EINVAL;

		goto bad_swap;

		goto bad_swap_unlock_inode;

	}

	}

	page = read_mapping_page(mapping, 0, swap_file);

	page = read_mapping_page(mapping, 0, swap_file);

	if (IS_ERR(page)) {

	if (IS_ERR(page)) {

		error = PTR_ERR(page);

		error = PTR_ERR(page);

		goto bad_swap;

		goto bad_swap_unlock_inode;

	}

	}

	swap_header = kmap(page);

	swap_header = kmap(page);





	maxpages = read_swap_header(p, swap_header, inode);

	maxpages = read_swap_header(p, swap_header, inode);

	if (unlikely(!maxpages)) {

	if (unlikely(!maxpages)) {

		error = -EINVAL;

		error = -EINVAL;

		goto bad_swap;

		goto bad_swap_unlock_inode;

	}

	}





	/* OK, set up the swap map and apply the bad block list */

	/* OK, set up the swap map and apply the bad block list */

	swap_map = vzalloc(maxpages);

	swap_map = vzalloc(maxpages);

	if (!swap_map) {

	if (!swap_map) {

		error = -ENOMEM;

		error = -ENOMEM;

		goto bad_swap;

		goto bad_swap_unlock_inode;

	}

	}





	if (bdi_cap_stable_pages_required(inode_to_bdi(inode)))

	if (bdi_cap_stable_pages_required(inode_to_bdi(inode)))
@@ -3228,7 +3229,7 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags) 
					GFP_KERNEL);

					GFP_KERNEL);

		if (!cluster_info) {

		if (!cluster_info) {

			error = -ENOMEM;

			error = -ENOMEM;

			goto bad_swap;

			goto bad_swap_unlock_inode;

		}

		}





		for (ci = 0; ci < nr_cluster; ci++)

		for (ci = 0; ci < nr_cluster; ci++)
@@ -3237,7 +3238,7 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags) 
		p->percpu_cluster = alloc_percpu(struct percpu_cluster);

		p->percpu_cluster = alloc_percpu(struct percpu_cluster);

		if (!p->percpu_cluster) {

		if (!p->percpu_cluster) {

			error = -ENOMEM;

			error = -ENOMEM;

			goto bad_swap;

			goto bad_swap_unlock_inode;

		}

		}

		for_each_possible_cpu(cpu) {

		for_each_possible_cpu(cpu) {

			struct percpu_cluster *cluster;

			struct percpu_cluster *cluster;
@@ -3251,13 +3252,13 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags) 




	error = swap_cgroup_swapon(p->type, maxpages);

	error = swap_cgroup_swapon(p->type, maxpages);

	if (error)

	if (error)

		goto bad_swap;

		goto bad_swap_unlock_inode;





	nr_extents = setup_swap_map_and_extents(p, swap_header, swap_map,

	nr_extents = setup_swap_map_and_extents(p, swap_header, swap_map,

		cluster_info, maxpages, &span);

		cluster_info, maxpages, &span);

	if (unlikely(nr_extents < 0)) {

	if (unlikely(nr_extents < 0)) {

		error = nr_extents;

		error = nr_extents;

		goto bad_swap;

		goto bad_swap_unlock_inode;

	}

	}

	/* frontswap enabled? set up bit-per-page map for frontswap */

	/* frontswap enabled? set up bit-per-page map for frontswap */

	if (IS_ENABLED(CONFIG_FRONTSWAP))

	if (IS_ENABLED(CONFIG_FRONTSWAP))
@@ -3297,7 +3298,7 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags) 




	error = init_swap_address_space(p->type, maxpages);

	error = init_swap_address_space(p->type, maxpages);

	if (error)

	if (error)

		goto bad_swap;

		goto bad_swap_unlock_inode;





	/*

	/*

	 * Flush any pending IO and dirty mappings before we start using this

	 * Flush any pending IO and dirty mappings before we start using this
@@ -3307,7 +3308,7 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags) 
	error = inode_drain_writes(inode);

	error = inode_drain_writes(inode);

	if (error) {

	if (error) {

		inode->i_flags &= ~S_SWAPFILE;

		inode->i_flags &= ~S_SWAPFILE;

		goto bad_swap;

		goto bad_swap_unlock_inode;

	}

	}





	mutex_lock(&swapon_mutex);

	mutex_lock(&swapon_mutex);
@@ -3334,6 +3335,8 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags) 




	error = 0;

	error = 0;

	goto out;

	goto out;

bad_swap_unlock_inode:

	inode_unlock(inode);

bad_swap:

bad_swap:

	free_percpu(p->percpu_cluster);

	free_percpu(p->percpu_cluster);

	p->percpu_cluster = NULL;

	p->percpu_cluster = NULL;
@@ -3341,6 +3344,7 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags) 
		set_blocksize(p->bdev, p->old_block_size);

		set_blocksize(p->bdev, p->old_block_size);

		blkdev_put(p->bdev, FMODE_READ | FMODE_WRITE | FMODE_EXCL);

		blkdev_put(p->bdev, FMODE_READ | FMODE_WRITE | FMODE_EXCL);

	}

	}

	inode = NULL;

	destroy_swap_extents(p);

	destroy_swap_extents(p);

	swap_cgroup_swapoff(p->type);

	swap_cgroup_swapoff(p->type);

	spin_lock(&swap_lock);

	spin_lock(&swap_lock);
@@ -3352,13 +3356,8 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags) 
	kvfree(frontswap_map);

	kvfree(frontswap_map);

	if (inced_nr_rotate_swap)

	if (inced_nr_rotate_swap)

		atomic_dec(&nr_rotate_swap);

		atomic_dec(&nr_rotate_swap);

	if (swap_file) {

	if (swap_file)

		if (inode) {

			inode_unlock(inode);

			inode = NULL;

		}

		filp_close(swap_file, NULL);

		filp_close(swap_file, NULL);

	}

out:

out:

	if (page && !IS_ERR(page)) {

	if (page && !IS_ERR(page)) {

		kunmap(page);

		kunmap(page);