On Tue, Mar 24, 2020 at 06:59:08AM +0900, Naohiro Aota wrote: > On Mon, Mar 23, 2020 at 02:12:01PM -0700, Darrick J. Wong wrote: > > On Mon, Mar 23, 2020 at 02:06:15PM -0700, Andrew Morton wrote: > > > On Mon, 23 Mar 2020 15:30:45 +0000 Qais Yousef <qais.yousef@xxxxxxx> wrote: > > > > > > > On 03/23/20 15:17, Qais Yousef wrote: > > > > > Hi > > > > > > > > > > I hit the following 2 warnings when running with LOCKDEP=y on arm64 platform > > > > > (juno-r2), running on v5.6-rc6 > > > > > > > > > > The 1st one is when I execute `swapon -a`. The 2nd one happens at boot. I have > > > > > /dev/sda2 as my swap in /etc/fstab > > > > > > > > > > Note that I either hit 1 OR 2, but didn't hit both warnings at the same time, > > > > > yet at least. > > > > > > > > > > /dev/sda2 is a usb flash drive, in case it matters somehow. > > > > > > > > By the way, I noticed that in claim_swapfile() if we fail we don't release the > > > > lock. Shouldn't we release the lock here? > > > > > > > > I tried with that FWIW, but it had no effect on the warnings. > > > > > > > > > > I'll be sending the below into Linus this week. > > > > > > I was hoping to hear from Darrick/Christoph (?) but it looks like the > > > right thing to do. Are you able to test it? > > > > I had questions[1] about the patch, but nobody ever replied. > > Sorry, I have overlooked that one. I'm replying here. > > > Sorry to wander in late, but I don't see how we unlock the inode in the > > success case. Before this patch, the "if (inode) inode_unlock(inode);" > > below out: would take care of this for both the success case and the > > bad_swap case, but now that's gone, and AFAICT after this patch we only > > unlock the inode when erroring out... > > > > > +bad_swap_unlock_inode: > > > + inode_unlock(inode); > > > > ...since we never goto bad_swap_unlock_inode when error == 0, correct? > > Actually, this patch does not touch "if (inode) inode_unlock(inode);" below > the "out:" label, so we still have that "inode_unlock" after this patch and > it unlocks the inode in the success case. Ah, right, I don't know what I was thinking when I wrote that. :) Reviewed-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx> --D > > > > > --D > > > > [1] https://lore.kernel.org/linux-fsdevel/20200212164956.GK6874@magnolia/ > > > > > I think I'll add a cc:stable to this one. > > > > > > > > > > > > From: Naohiro Aota <naohiro.aota@xxxxxxx> > > > Subject: 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: > > > [<ffffffff8173a6eb>] __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 > > > ? __do_sys_swapon+0x94b/0x3550 > > > print_unlock_imbalance_bug.cold+0x114/0x123 > > > ? __do_sys_swapon+0x94b/0x3550 > > > lock_release+0x562/0xed0 > > > ? kvfree+0x31/0x40 > > > ? lock_downgrade+0x770/0x770 > > > ? kvfree+0x31/0x40 > > > ? rcu_read_lock_sched_held+0xa1/0xd0 > > > ? rcu_read_lock_bh_held+0xb0/0xb0 > > > up_write+0x2d/0x490 > > > ? kfree+0x293/0x2f0 > > > __do_sys_swapon+0x94b/0x3550 > > > ? putname+0xb0/0xf0 > > > ? kmem_cache_free+0x2e7/0x370 > > > ? do_sys_open+0x184/0x3e0 > > > ? generic_max_swapfile_size+0x40/0x40 > > > ? do_syscall_64+0x27/0x4b0 > > > ? entry_SYSCALL_64_after_hwframe+0x49/0xbe > > > ? lockdep_hardirqs_on+0x38c/0x590 > > > __x64_sys_swapon+0x54/0x80 > > > do_syscall_64+0xa4/0x4b0 > > > entry_SYSCALL_64_after_hwframe+0x49/0xbe > > > RIP: 0033:0x7f15da0a0dc7 > > > > > > Link: http://lkml.kernel.org/r/20200206090132.154869-1-naohiro.aota@xxxxxxx > > > Fixes: 1638045c3677 ("mm: set S_SWAPFILE on blockdev swap devices") > > > Signed-off-by: Naohiro Aota <naohiro.aota@xxxxxxx> > > > Reviewed-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> > > > Cc: Darrick J. Wong <darrick.wong@xxxxxxxxxx> > > > Cc: Christoph Hellwig <hch@xxxxxxxxxxxxx> > > > Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> > > > --- > > > > > > mm/swapfile.c | 41 ++++++++++++++++++++--------------------- > > > 1 file changed, 20 insertions(+), 21 deletions(-) > > > > > > --- a/mm/swapfile.c~mm-swap-move-inode_lock-out-of-claim_swapfile > > > +++ a/mm/swapfile.c > > > @@ -2899,10 +2899,6 @@ static int claim_swapfile(struct swap_in > > > p->bdev = inode->i_sb->s_bdev; > > > } > > > > > > - inode_lock(inode); > > > - if (IS_SWAPFILE(inode)) > > > - return -EBUSY; > > > - > > > return 0; > > > } > > > > > > @@ -3157,36 +3153,41 @@ SYSCALL_DEFINE2(swapon, const char __use > > > mapping = swap_file->f_mapping; > > > inode = mapping->host; > > > > > > - /* will take i_rwsem; */ > > > error = claim_swapfile(p, inode); > > > if (unlikely(error)) > > > goto bad_swap; > > > > > > + inode_lock(inode); > > > + if (IS_SWAPFILE(inode)) { > > > + error = -EBUSY; > > > + goto bad_swap_unlock_inode; > > > + } > > > + > > > /* > > > * Read the swap header. > > > */ > > > if (!mapping->a_ops->readpage) { > > > error = -EINVAL; > > > - goto bad_swap; > > > + goto bad_swap_unlock_inode; > > > } > > > page = read_mapping_page(mapping, 0, swap_file); > > > if (IS_ERR(page)) { > > > error = PTR_ERR(page); > > > - goto bad_swap; > > > + goto bad_swap_unlock_inode; > > > } > > > swap_header = kmap(page); > > > > > > maxpages = read_swap_header(p, swap_header, inode); > > > if (unlikely(!maxpages)) { > > > error = -EINVAL; > > > - goto bad_swap; > > > + goto bad_swap_unlock_inode; > > > } > > > > > > /* OK, set up the swap map and apply the bad block list */ > > > swap_map = vzalloc(maxpages); > > > if (!swap_map) { > > > error = -ENOMEM; > > > - goto bad_swap; > > > + goto bad_swap_unlock_inode; > > > } > > > > > > if (bdi_cap_stable_pages_required(inode_to_bdi(inode))) > > > @@ -3211,7 +3212,7 @@ SYSCALL_DEFINE2(swapon, const char __use > > > GFP_KERNEL); > > > if (!cluster_info) { > > > error = -ENOMEM; > > > - goto bad_swap; > > > + goto bad_swap_unlock_inode; > > > } > > > > > > for (ci = 0; ci < nr_cluster; ci++) > > > @@ -3220,7 +3221,7 @@ SYSCALL_DEFINE2(swapon, const char __use > > > p->percpu_cluster = alloc_percpu(struct percpu_cluster); > > > if (!p->percpu_cluster) { > > > error = -ENOMEM; > > > - goto bad_swap; > > > + goto bad_swap_unlock_inode; > > > } > > > for_each_possible_cpu(cpu) { > > > struct percpu_cluster *cluster; > > > @@ -3234,13 +3235,13 @@ SYSCALL_DEFINE2(swapon, const char __use > > > > > > error = swap_cgroup_swapon(p->type, maxpages); > > > if (error) > > > - goto bad_swap; > > > + goto bad_swap_unlock_inode; > > > > > > nr_extents = setup_swap_map_and_extents(p, swap_header, swap_map, > > > cluster_info, maxpages, &span); > > > if (unlikely(nr_extents < 0)) { > > > error = nr_extents; > > > - goto bad_swap; > > > + goto bad_swap_unlock_inode; > > > } > > > /* frontswap enabled? set up bit-per-page map for frontswap */ > > > if (IS_ENABLED(CONFIG_FRONTSWAP)) > > > @@ -3280,7 +3281,7 @@ SYSCALL_DEFINE2(swapon, const char __use > > > > > > error = init_swap_address_space(p->type, maxpages); > > > if (error) > > > - goto bad_swap; > > > + goto bad_swap_unlock_inode; > > > > > > /* > > > * Flush any pending IO and dirty mappings before we start using this > > > @@ -3290,7 +3291,7 @@ SYSCALL_DEFINE2(swapon, const char __use > > > error = inode_drain_writes(inode); > > > if (error) { > > > inode->i_flags &= ~S_SWAPFILE; > > > - goto bad_swap; > > > + goto bad_swap_unlock_inode; > > > } > > > > > > mutex_lock(&swapon_mutex); > > > @@ -3315,6 +3316,8 @@ SYSCALL_DEFINE2(swapon, const char __use > > > > > > error = 0; > > > goto out; > > > +bad_swap_unlock_inode: > > > + inode_unlock(inode); > > > bad_swap: > > > free_percpu(p->percpu_cluster); > > > p->percpu_cluster = NULL; > > > @@ -3322,6 +3325,7 @@ bad_swap: > > > set_blocksize(p->bdev, p->old_block_size); > > > blkdev_put(p->bdev, FMODE_READ | FMODE_WRITE | FMODE_EXCL); > > > } > > > + inode = NULL; > > > destroy_swap_extents(p); > > > swap_cgroup_swapoff(p->type); > > > spin_lock(&swap_lock); > > > @@ -3333,13 +3337,8 @@ bad_swap: > > > kvfree(frontswap_map); > > > if (inced_nr_rotate_swap) > > > atomic_dec(&nr_rotate_swap); > > > - if (swap_file) { > > > - if (inode) { > > > - inode_unlock(inode); > > > - inode = NULL; > > > - } > > > + if (swap_file) > > > filp_close(swap_file, NULL); > > > - } > > > out: > > > if (page && !IS_ERR(page)) { > > > kunmap(page); > > > _ > > >
