Re: [PATCH v5 1/2] ceph: switch to vfs_inode_has_locks() to fix file lock bug

[Xiubo Li <xiubli@redhat.com>]

On 15/12/2022 21:20, Ilya Dryomov wrote:
> On Wed, Dec 14, 2022 at 4:35 AM <xiubli@redhat.com> wrote:
>> From: Xiubo Li <xiubli@redhat.com>
>>
>> For the POSIX locks they are using the same owner, which is the
>> thread id. And multiple POSIX locks could be merged into single one,
>> so when checking whether the 'file' has locks may fail.
>>
>> For a file where some openers use locking and others don't is a
>> really odd usage pattern though. Locks are like stoplights -- they
>> only work if everyone pays attention to them.
>>
>> Just switch ceph_get_caps() to check whether any locks are set on
>> the inode. If there are POSIX/OFD/FLOCK locks on the file at the
>> time, we should set CHECK_FILELOCK, regardless of what fd was used
>> to set the lock.
>>
>> Cc: stable@vger.kernel.org
>> Cc: Jeff Layton <jlayton@kernel.org>
>> Fixes: ff5d913dfc71 ("ceph: return -EIO if read/write against filp that lost file locks")
>> Reviewed-by: Jeff Layton <jlayton@kernel.org>
>> Signed-off-by: Xiubo Li <xiubli@redhat.com>
>> ---
>>   fs/ceph/caps.c  | 2 +-
>>   fs/ceph/locks.c | 4 ----
>>   fs/ceph/super.h | 1 -
>>   3 files changed, 1 insertion(+), 6 deletions(-)
>>
>> diff --git a/fs/ceph/caps.c b/fs/ceph/caps.c
>> index 065e9311b607..948136f81fc8 100644
>> --- a/fs/ceph/caps.c
>> +++ b/fs/ceph/caps.c
>> @@ -2964,7 +2964,7 @@ int ceph_get_caps(struct file *filp, int need, int want, loff_t endoff, int *got
>>
>>          while (true) {
>>                  flags &= CEPH_FILE_MODE_MASK;
>> -               if (atomic_read(&fi->num_locks))
>> +               if (vfs_inode_has_locks(inode))
>>                          flags |= CHECK_FILELOCK;
>>                  _got = 0;
>>                  ret = try_get_cap_refs(inode, need, want, endoff,
>> diff --git a/fs/ceph/locks.c b/fs/ceph/locks.c
>> index 3e2843e86e27..b191426bf880 100644
>> --- a/fs/ceph/locks.c
>> +++ b/fs/ceph/locks.c
>> @@ -32,18 +32,14 @@ void __init ceph_flock_init(void)
>>
>>   static void ceph_fl_copy_lock(struct file_lock *dst, struct file_lock *src)
>>   {
>> -       struct ceph_file_info *fi = dst->fl_file->private_data;
>>          struct inode *inode = file_inode(dst->fl_file);
>>          atomic_inc(&ceph_inode(inode)->i_filelock_ref);
>> -       atomic_inc(&fi->num_locks);
>>   }
>>
>>   static void ceph_fl_release_lock(struct file_lock *fl)
>>   {
>> -       struct ceph_file_info *fi = fl->fl_file->private_data;
>>          struct inode *inode = file_inode(fl->fl_file);
>>          struct ceph_inode_info *ci = ceph_inode(inode);
>> -       atomic_dec(&fi->num_locks);
>>          if (atomic_dec_and_test(&ci->i_filelock_ref)) {
>>                  /* clear error when all locks are released */
>>                  spin_lock(&ci->i_ceph_lock);
>> diff --git a/fs/ceph/super.h b/fs/ceph/super.h
>> index 14454f464029..e7662ff6f149 100644
>> --- a/fs/ceph/super.h
>> +++ b/fs/ceph/super.h
>> @@ -804,7 +804,6 @@ struct ceph_file_info {
>>          struct list_head rw_contexts;
>>
>>          u32 filp_gen;
>> -       atomic_t num_locks;
>>   };
>>
>>   struct ceph_dir_file_info {
>> --
>> 2.31.1
>>
> Hi Xiubo,
>
> You marked this for stable but there is an obvious dependency on
> vfs_inode_has_locks() that just got merged for 6.2-rc1.  Are you
> intending to take it into stable kernels as well?

In the testing branch I just removed the stable list and will do the 
backport myself.

Thanks

- Xiubo


> Thanks,
>
>                  Ilya
>