[Virtio-fs] [PATCH 2/9] virtio-fs: clean up dax mapping before aborting connection

[Vivek Goyal]

On Wed, Apr 17, 2019 at 02:03:15AM +0800, Liu Bo wrote:
> fstests generic/127 reported that we failed to remove dax mapping during
> umount,

Is it still a problem with 0.2? I have fixed it by calling
fuse_removemapping_one() only if connection is still there
(fc->connected).

Had talked to miklos in the past and he preferred that virtiofs
daemon should have the capability to clean this up. It might
happen that guest does hard reboot and never cleans up ranges.

I think now David Gilbert has taken care of doing cleanup
on ->init and I think ->destroy as well. Have not looked
at the code closely.

Vivek

> 
> -----
> run fstests generic/127 at 2019-03-20 04:54:35
> fuse_removemapping_one request failed -107
> Failed to removemapping. offset=0x200000 len=0x200000
> -----
> 
> The root cause:
> virtio_kill_sb
>   -> fuse_kill_sb_anon
>     -> fuse_sb_destroy
>       -> fuse_abort_conn #fiq->connect = 0
>   -> kill_anon_super
>     -> fuse_evict_inode
>       -> fuse_removemapping
>         -> fuse_removemapping_one
>            # get -ENOTCONN, bail out
> 
> Unfortunately we have to make sure that all dax mappings linked in
> per-inode interval tree are moved back to fc->busy_ranges in order to
> avoid mapping leakage.
> 
> As we've tracked all dax mappings in fc->busy_ranges, this forces to free
> dax mappings before aborting connection.
> 
> Signed-off-by: Liu Bo <bo.liu at linux.alibaba.com>
> Reviewed-by: Joseph Qi <joseph.qi at linux.alibaba.com>
> ---
>  fs/fuse/fuse_i.h | 2 ++
>  fs/fuse/inode.c  | 9 +++++++++
>  2 files changed, 11 insertions(+)
> 
> diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h
> index 25e1e50..2c32846 100644
> --- a/fs/fuse/fuse_i.h
> +++ b/fs/fuse/fuse_i.h
> @@ -1202,4 +1202,6 @@ ssize_t fuse_getxattr(struct inode *inode, const char *name, void *value,
>  void fuse_dax_free_mem_worker(struct work_struct *work);
>  void fuse_removemapping(struct inode *inode);
>  
> +int fuse_dax_free_memory(struct fuse_conn *fc, unsigned long nr_to_free);
> +
>  #endif /* _FS_FUSE_I_H */
> diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
> index 6e96613..22d5f6a 100644
> --- a/fs/fuse/inode.c
> +++ b/fs/fuse/inode.c
> @@ -1378,6 +1378,15 @@ static void fuse_sb_destroy(struct super_block *sb)
>  	if (fc) {
>  		fuse_send_destroy(fc);
>  
> +		/* cleanup dax mapping ranges before aborting connection. */
> +		spin_lock(&fc->lock);
> +		if (fc->nr_busy_ranges) {
> +			spin_unlock(&fc->lock);
> +			fuse_dax_free_memory(fc, -1UL);
> +		} else {
> +			spin_unlock(&fc->lock);
> +		}
> +
>  		fuse_abort_conn(fc, false);
>  		fuse_wait_aborted(fc);
>  
> -- 
> 1.8.3.1
> 
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