Re: [RFC PATCH 4/6] xfs: take i_mmap_lock on extent manipulation operations

[Brian Foster <bfoster@redhat.com>]

On Thu, Jan 08, 2015 at 09:25:41AM +1100, Dave Chinner wrote:
> From: Dave Chinner <dchinner@redhat.com>
> 
> Now we have the i_mmap_lock being held across the page fault IO
> path, we now add extent manipulation operation exclusion by adding
> the lock to the paths that directly modify extent maps. This
> includes truncate, hole punching and other fallocate based
> operations. The operations will now take both the i_iolock and the
> i_mmaplock in exclusive mode, thereby ensuring that all IO and page
> faults block without holding any page locks while the extent
> manipulation is in progress.
> 
> This gives us the lock order during truncate of i_iolock ->
> i_mmaplock -> page_lock -> i_lock, hence providing the same
> lock order as the iolock provides the normal IO path without
> involving the mmap_sem.
> 
> Signed-off-by: Dave Chinner <dchinner@redhat.com>
> ---
>  fs/xfs/xfs_file.c  | 4 ++--
>  fs/xfs/xfs_ioctl.c | 4 ++--
>  fs/xfs/xfs_iops.c  | 6 +++---
>  3 files changed, 7 insertions(+), 7 deletions(-)
> 
> diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
> index e6e7e75..b08c9e6 100644
> --- a/fs/xfs/xfs_file.c
> +++ b/fs/xfs/xfs_file.c
> @@ -794,7 +794,7 @@ xfs_file_fallocate(
>  		     FALLOC_FL_COLLAPSE_RANGE | FALLOC_FL_ZERO_RANGE))
>  		return -EOPNOTSUPP;
>  
> -	xfs_ilock(ip, XFS_IOLOCK_EXCL);
> +	xfs_ilock(ip, XFS_IOLOCK_EXCL|XFS_MMAPLOCK_EXCL);
>  	if (mode & FALLOC_FL_PUNCH_HOLE) {
>  		error = xfs_free_file_space(ip, offset, len);
>  		if (error)
> @@ -874,7 +874,7 @@ xfs_file_fallocate(
>  	}
>  
>  out_unlock:
> -	xfs_iunlock(ip, XFS_IOLOCK_EXCL);
> +	xfs_iunlock(ip, XFS_IOLOCK_EXCL|XFS_MMAPLOCK_EXCL);
>  	return error;
>  }
>  
> diff --git a/fs/xfs/xfs_ioctl.c b/fs/xfs/xfs_ioctl.c
> index a183198..8810959 100644
> --- a/fs/xfs/xfs_ioctl.c
> +++ b/fs/xfs/xfs_ioctl.c
> @@ -634,7 +634,7 @@ xfs_ioc_space(
>  	if (error)
>  		return error;
>  
> -	xfs_ilock(ip, XFS_IOLOCK_EXCL);
> +	xfs_ilock(ip, XFS_IOLOCK_EXCL|XFS_MMAPLOCK_EXCL);
>  
>  	switch (bf->l_whence) {
>  	case 0: /*SEEK_SET*/
> @@ -751,7 +751,7 @@ xfs_ioc_space(
>  	error = xfs_trans_commit(tp, 0);
>  
>  out_unlock:
> -	xfs_iunlock(ip, XFS_IOLOCK_EXCL);
> +	xfs_iunlock(ip, XFS_IOLOCK_EXCL|XFS_MMAPLOCK_EXCL);
>  	mnt_drop_write_file(filp);
>  	return error;
>  }
> diff --git a/fs/xfs/xfs_iops.c b/fs/xfs/xfs_iops.c
> index 8be5bb5..f491860 100644
> --- a/fs/xfs/xfs_iops.c
> +++ b/fs/xfs/xfs_iops.c
> @@ -768,7 +768,7 @@ xfs_setattr_size(
>  	if (error)
>  		return error;
>  
> -	ASSERT(xfs_isilocked(ip, XFS_IOLOCK_EXCL));
> +	ASSERT(xfs_isilocked(ip, XFS_IOLOCK_EXCL|XFS_MMAPLOCK_EXCL));

Only debug code of course, but xfs_isilocked() doesn't appear to support
what is intended by this call (e.g., verification of multiple locks).

Brian

>  	ASSERT(S_ISREG(ip->i_d.di_mode));
>  	ASSERT((iattr->ia_valid & (ATTR_UID|ATTR_GID|ATTR_ATIME|ATTR_ATIME_SET|
>  		ATTR_MTIME_SET|ATTR_KILL_PRIV|ATTR_TIMES_SET)) == 0);
> @@ -984,9 +984,9 @@ xfs_vn_setattr(
>  	int			error;
>  
>  	if (iattr->ia_valid & ATTR_SIZE) {
> -		xfs_ilock(ip, XFS_IOLOCK_EXCL);
> +		xfs_ilock(ip, XFS_IOLOCK_EXCL|XFS_MMAPLOCK_EXCL);
>  		error = xfs_setattr_size(ip, iattr);
> -		xfs_iunlock(ip, XFS_IOLOCK_EXCL);
> +		xfs_iunlock(ip, XFS_IOLOCK_EXCL|XFS_MMAPLOCK_EXCL);
>  	} else {
>  		error = xfs_setattr_nonsize(ip, iattr, 0);
>  	}
> -- 
> 2.0.0
> 
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