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authorTejun Heo <tj@kernel.org>2016-02-16 11:34:07 -0700
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2016-03-03 15:07:28 -0800
commit7c465723d0b6f2621f6c712035b117d744a51a8b (patch)
treea4e5e7a0b9e4cd7f82797059f3eb47706a00b68a /fs/fs-writeback.c
parent4cbd196324c05809338c7f118b6f374d3c2db7a0 (diff)
writeback: keep superblock pinned during cgroup writeback association switches
commit 5ff8eaac1636bf6deae86491f4818c4c69d1a9ac upstream. If cgroup writeback is in use, an inode is associated with a cgroup for writeback. If the inode's main dirtier changes to another cgroup, the association gets updated asynchronously. Nothing was pinning the superblock while such switches are in progress and superblock could go away while async switching is pending or in progress leading to crashes like the following. kernel BUG at fs/jbd2/transaction.c:319! invalid opcode: 0000 [#1] SMP DEBUG_PAGEALLOC CPU: 1 PID: 29158 Comm: kworker/1:10 Not tainted 4.5.0-rc3 #51 Hardware name: Google Google, BIOS Google 01/01/2011 Workqueue: events inode_switch_wbs_work_fn task: ffff880213dbbd40 ti: ffff880209264000 task.ti: ffff880209264000 RIP: 0010:[<ffffffff803e6922>] [<ffffffff803e6922>] start_this_handle+0x382/0x3e0 RSP: 0018:ffff880209267c30 EFLAGS: 00010202 ... Call Trace: [<ffffffff803e6be4>] jbd2__journal_start+0xf4/0x190 [<ffffffff803cfc7e>] __ext4_journal_start_sb+0x4e/0x70 [<ffffffff803b31ec>] ext4_evict_inode+0x12c/0x3d0 [<ffffffff8035338b>] evict+0xbb/0x190 [<ffffffff80354190>] iput+0x130/0x190 [<ffffffff80360223>] inode_switch_wbs_work_fn+0x343/0x4c0 [<ffffffff80279819>] process_one_work+0x129/0x300 [<ffffffff80279b16>] worker_thread+0x126/0x480 [<ffffffff8027ed14>] kthread+0xc4/0xe0 [<ffffffff809771df>] ret_from_fork+0x3f/0x70 Fix it by bumping s_active while cgroup association switching is in flight. Signed-off-by: Tejun Heo <tj@kernel.org> Reported-and-tested-by: Tahsin Erdogan <tahsin@google.com> Link: http://lkml.kernel.org/g/CAAeU0aNCq7LGODvVGRU-oU_o-6enii5ey0p1c26D1ZzYwkDc5A@mail.gmail.com Fixes: d10c80955265 ("writeback: implement foreign cgroup inode bdi_writeback switching") Signed-off-by: Jens Axboe <axboe@fb.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'fs/fs-writeback.c')
-rw-r--r--fs/fs-writeback.c15
1 files changed, 11 insertions, 4 deletions
diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index 023f6a1f23cd..e5232bbcbe3d 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -317,6 +317,7 @@ static void inode_switch_wbs_work_fn(struct work_struct *work)
struct inode_switch_wbs_context *isw =
container_of(work, struct inode_switch_wbs_context, work);
struct inode *inode = isw->inode;
+ struct super_block *sb = inode->i_sb;
struct address_space *mapping = inode->i_mapping;
struct bdi_writeback *old_wb = inode->i_wb;
struct bdi_writeback *new_wb = isw->new_wb;
@@ -423,6 +424,7 @@ skip_switch:
wb_put(new_wb);
iput(inode);
+ deactivate_super(sb);
kfree(isw);
}
@@ -469,11 +471,14 @@ static void inode_switch_wbs(struct inode *inode, int new_wb_id)
/* while holding I_WB_SWITCH, no one else can update the association */
spin_lock(&inode->i_lock);
+
if (inode->i_state & (I_WB_SWITCH | I_FREEING) ||
- inode_to_wb(inode) == isw->new_wb) {
- spin_unlock(&inode->i_lock);
- goto out_free;
- }
+ inode_to_wb(inode) == isw->new_wb)
+ goto out_unlock;
+
+ if (!atomic_inc_not_zero(&inode->i_sb->s_active))
+ goto out_unlock;
+
inode->i_state |= I_WB_SWITCH;
spin_unlock(&inode->i_lock);
@@ -489,6 +494,8 @@ static void inode_switch_wbs(struct inode *inode, int new_wb_id)
call_rcu(&isw->rcu_head, inode_switch_wbs_rcu_fn);
return;
+out_unlock:
+ spin_unlock(&inode->i_lock);
out_free:
if (isw->new_wb)
wb_put(isw->new_wb);