linux-cifs.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Dave Chinner <david@fromorbit.com>
To: Jan Kara <jack@suse.cz>
Cc: linux-fsdevel@vger.kernel.org,
	Christoph Hellwig <hch@infradead.org>,
	ceph-devel@vger.kernel.org, Chao Yu <yuchao0@huawei.com>,
	Damien Le Moal <damien.lemoal@wdc.com>,
	"Darrick J. Wong" <darrick.wong@oracle.com>,
	Jaegeuk Kim <jaegeuk@kernel.org>,
	Jeff Layton <jlayton@kernel.org>,
	Johannes Thumshirn <jth@kernel.org>,
	linux-cifs@vger.kernel.org, linux-ext4@vger.kernel.org,
	linux-f2fs-devel@lists.sourceforge.net, linux-mm@kvack.org,
	linux-xfs@vger.kernel.org, Miklos Szeredi <miklos@szeredi.hu>,
	Steve French <sfrench@samba.org>, Ted Tso <tytso@mit.edu>,
	Matthew Wilcox <willy@infradead.org>,
	Christoph Hellwig <hch@lst.de>
Subject: Re: [PATCH 07/13] xfs: Convert to use invalidate_lock
Date: Wed, 26 May 2021 07:40:41 +1000	[thread overview]
Message-ID: <20210525214041.GJ664593@dread.disaster.area> (raw)
In-Reply-To: <20210525135100.11221-7-jack@suse.cz>

On Tue, May 25, 2021 at 03:50:44PM +0200, Jan Kara wrote:
> Use invalidate_lock instead of XFS internal i_mmap_lock. The intended
> purpose of invalidate_lock is exactly the same. Note that the locking in
> __xfs_filemap_fault() slightly changes as filemap_fault() already takes
> invalidate_lock.
> 
> Reviewed-by: Christoph Hellwig <hch@lst.de>
> CC: <linux-xfs@vger.kernel.org>
> CC: "Darrick J. Wong" <darrick.wong@oracle.com>
> Signed-off-by: Jan Kara <jack@suse.cz>
> ---
>  fs/xfs/xfs_file.c  | 12 ++++++-----
>  fs/xfs/xfs_inode.c | 52 ++++++++++++++++++++++++++--------------------
>  fs/xfs/xfs_inode.h |  1 -
>  fs/xfs/xfs_super.c |  2 --
>  4 files changed, 36 insertions(+), 31 deletions(-)
> 
> diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
> index 396ef36dcd0a..dc9cb5c20549 100644
> --- a/fs/xfs/xfs_file.c
> +++ b/fs/xfs/xfs_file.c
> @@ -1282,7 +1282,7 @@ xfs_file_llseek(
>   *
>   * mmap_lock (MM)
>   *   sb_start_pagefault(vfs, freeze)
> - *     i_mmaplock (XFS - truncate serialisation)
> + *     invalidate_lock (vfs/XFS_MMAPLOCK - truncate serialisation)
>   *       page_lock (MM)
>   *         i_lock (XFS - extent map serialisation)
>   */
> @@ -1303,24 +1303,26 @@ __xfs_filemap_fault(
>  		file_update_time(vmf->vma->vm_file);
>  	}
>  
> -	xfs_ilock(XFS_I(inode), XFS_MMAPLOCK_SHARED);
>  	if (IS_DAX(inode)) {
>  		pfn_t pfn;
>  
> +		xfs_ilock(XFS_I(inode), XFS_MMAPLOCK_SHARED);
>  		ret = dax_iomap_fault(vmf, pe_size, &pfn, NULL,
>  				(write_fault && !vmf->cow_page) ?
>  				 &xfs_direct_write_iomap_ops :
>  				 &xfs_read_iomap_ops);
>  		if (ret & VM_FAULT_NEEDDSYNC)
>  			ret = dax_finish_sync_fault(vmf, pe_size, pfn);
> +		xfs_iunlock(XFS_I(inode), XFS_MMAPLOCK_SHARED);
>  	} else {
> -		if (write_fault)
> +		if (write_fault) {
> +			xfs_ilock(XFS_I(inode), XFS_MMAPLOCK_SHARED);
>  			ret = iomap_page_mkwrite(vmf,
>  					&xfs_buffered_write_iomap_ops);
> -		else
> +			xfs_iunlock(XFS_I(inode), XFS_MMAPLOCK_SHARED);
> +		} else
>  			ret = filemap_fault(vmf);
>  	}
> -	xfs_iunlock(XFS_I(inode), XFS_MMAPLOCK_SHARED);

This seems kinda messy. filemap_fault() basically takes the
invalidate lock around the entire operation, it runs, so maybe it
would be cleaner to implement it as:

filemap_fault_locked(vmf)
{
	/* does the filemap fault work */
}

filemap_fault(vmf)
{
	filemap_invalidate_down_read(...)
	ret = filemap_fault_locked(vmf)
	filemap_invalidate_up_read(...)
	return ret;
}

And that means XFS could just call filemap_fault_locked() and not 
have to do all this messy locking just to avoid holding the lock
that filemap_fault has now internalised.

> @@ -355,8 +358,11 @@ xfs_isilocked(
>  
>  	if (lock_flags & (XFS_MMAPLOCK_EXCL|XFS_MMAPLOCK_SHARED)) {
>  		if (!(lock_flags & XFS_MMAPLOCK_SHARED))
> -			return !!ip->i_mmaplock.mr_writer;
> -		return rwsem_is_locked(&ip->i_mmaplock.mr_lock);
> +			return !debug_locks ||
> +				lockdep_is_held_type(
> +					&VFS_I(ip)->i_mapping->invalidate_lock,
> +					0);
> +		return rwsem_is_locked(&VFS_I(ip)->i_mapping->invalidate_lock);
>  	}

<sigh>

And so here we are again, losing more of our read vs write debug
checks on debug kernels when lockdep is not enabled....

Can we please add rwsem_is_locked_read() and rwsem_is_locked_write()
wrappers that just look at the rwsem counter value to determine how
the lock is held? Then the mrlock_t can go away entirely....

Cheers,

Dave.
-- 
Dave Chinner
david@fromorbit.com

  parent reply	other threads:[~2021-05-25 21:40 UTC|newest]

Thread overview: 31+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-05-25 13:50 [PATCH 0/13 v6] fs: Hole punch vs page cache filling races Jan Kara
2021-05-25 13:50 ` [PATCH 01/13] mm: Fix comments mentioning i_mutex Jan Kara
2021-05-25 13:50 ` [PATCH 02/13] documentation: Sync file_operations members with reality Jan Kara
2021-05-25 20:43   ` Darrick J. Wong
2021-05-25 13:50 ` [PATCH 03/13] mm: Protect operations adding pages to page cache with invalidate_lock Jan Kara
2021-05-25 21:01   ` Darrick J. Wong
2021-05-26 10:00     ` Jan Kara
2021-05-25 13:50 ` [PATCH 04/13] mm: Add functions to lock invalidate_lock for two mappings Jan Kara
2021-05-25 20:48   ` Darrick J. Wong
2021-05-26 10:07     ` Jan Kara
2021-05-26 12:11       ` Damien Le Moal
2021-05-26 13:45         ` Jan Kara
2021-05-26 15:25           ` Darrick J. Wong
2021-05-25 13:50 ` [PATCH 05/13] ext4: Convert to use mapping->invalidate_lock Jan Kara
2021-05-25 13:50 ` [PATCH 06/13] ext2: Convert to using invalidate_lock Jan Kara
2021-05-25 13:50 ` [PATCH 07/13] xfs: Convert to use invalidate_lock Jan Kara
2021-05-25 21:37   ` Darrick J. Wong
2021-05-26 10:18     ` Jan Kara
2021-05-26 15:32       ` Darrick J. Wong
2021-05-27 12:01         ` Jan Kara
2021-05-25 21:40   ` Dave Chinner [this message]
2021-05-26 10:20     ` Jan Kara
2021-05-26 13:42       ` Jan Kara
2021-05-25 13:50 ` [PATCH 08/13] xfs: Convert double locking of MMAPLOCK to use VFS helpers Jan Kara
2021-05-25 21:41   ` Darrick J. Wong
2021-05-25 13:50 ` [PATCH 09/13] zonefs: Convert to using invalidate_lock Jan Kara
2021-05-25 13:50 ` [PATCH 10/13] f2fs: " Jan Kara
2021-05-26  9:55   ` Chao Yu
2021-05-25 13:50 ` [PATCH 11/13] fuse: " Jan Kara
2021-05-25 13:50 ` [PATCH 12/13] ceph: Fix race between hole punch and page fault Jan Kara
2021-05-25 13:50 ` [PATCH 13/13] cifs: " Jan Kara

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20210525214041.GJ664593@dread.disaster.area \
    --to=david@fromorbit.com \
    --cc=ceph-devel@vger.kernel.org \
    --cc=damien.lemoal@wdc.com \
    --cc=darrick.wong@oracle.com \
    --cc=hch@infradead.org \
    --cc=hch@lst.de \
    --cc=jack@suse.cz \
    --cc=jaegeuk@kernel.org \
    --cc=jlayton@kernel.org \
    --cc=jth@kernel.org \
    --cc=linux-cifs@vger.kernel.org \
    --cc=linux-ext4@vger.kernel.org \
    --cc=linux-f2fs-devel@lists.sourceforge.net \
    --cc=linux-fsdevel@vger.kernel.org \
    --cc=linux-mm@kvack.org \
    --cc=linux-xfs@vger.kernel.org \
    --cc=miklos@szeredi.hu \
    --cc=sfrench@samba.org \
    --cc=tytso@mit.edu \
    --cc=willy@infradead.org \
    --cc=yuchao0@huawei.com \
    --subject='Re: [PATCH 07/13] xfs: Convert to use invalidate_lock' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).