From: Matthew Wilcox <willy@infradead.org>
To: Jan Kara <jack@suse.cz>
Cc: linux-fsdevel@vger.kernel.org,
Christoph Hellwig <hch@infradead.org>,
Dave Chinner <david@fromorbit.com>,
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>
Subject: Re: [PATCH 03/11] mm: Protect operations adding pages to page cache with invalidate_lock
Date: Wed, 12 May 2021 15:40:21 +0100 [thread overview]
Message-ID: <YJvo1bGG1tG+gtgC@casper.infradead.org> (raw)
In-Reply-To: <20210512134631.4053-3-jack@suse.cz>
On Wed, May 12, 2021 at 03:46:11PM +0200, Jan Kara wrote:
> Currently, serializing operations such as page fault, read, or readahead
> against hole punching is rather difficult. The basic race scheme is
> like:
>
> fallocate(FALLOC_FL_PUNCH_HOLE) read / fault / ..
> truncate_inode_pages_range()
> <create pages in page
> cache here>
> <update fs block mapping and free blocks>
>
> Now the problem is in this way read / page fault / readahead can
> instantiate pages in page cache with potentially stale data (if blocks
> get quickly reused). Avoiding this race is not simple - page locks do
> not work because we want to make sure there are *no* pages in given
> range. inode->i_rwsem does not work because page fault happens under
> mmap_sem which ranks below inode->i_rwsem. Also using it for reads makes
> the performance for mixed read-write workloads suffer.
>
> So create a new rw_semaphore in the address_space - invalidate_lock -
> that protects adding of pages to page cache for page faults / reads /
> readahead.
Remind me (or, rather, add to the documentation) why we have to hold the
invalidate_lock during the call to readpage / readahead, and we don't just
hold it around the call to add_to_page_cache / add_to_page_cache_locked
/ add_to_page_cache_lru ? I appreciate that ->readpages is still going
to suck, but we're down to just three implementations of ->readpages now
(9p, cifs & nfs).
Also, could I trouble you to run the comments through 'fmt' (or
equivalent)? It's easier to read if you're not kissing right up on 80
columns.
> +++ b/fs/inode.c
> @@ -190,6 +190,9 @@ int inode_init_always(struct super_block *sb, struct inode *inode)
> mapping_set_gfp_mask(mapping, GFP_HIGHUSER_MOVABLE);
> mapping->private_data = NULL;
> mapping->writeback_index = 0;
> + init_rwsem(&mapping->invalidate_lock);
> + lockdep_set_class(&mapping->invalidate_lock,
> + &sb->s_type->invalidate_lock_key);
Why not:
__init_rwsem(&mapping->invalidate_lock, "mapping.invalidate_lock",
&sb->s_type->invalidate_lock_key);
next prev parent reply other threads:[~2021-05-12 14:41 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-12 13:46 [PATCH 0/11 v5] fs: Hole punch vs page cache filling races Jan Kara
2021-05-12 13:46 ` [PATCH 01/11] mm: Fix comments mentioning i_mutex Jan Kara
2021-05-12 13:46 ` [PATCH 02/11] documentation: Sync file_operations members with reality Jan Kara
2021-05-12 13:46 ` [PATCH 03/11] mm: Protect operations adding pages to page cache with invalidate_lock Jan Kara
2021-05-12 14:20 ` Matthew Wilcox
2021-05-13 17:49 ` Jan Kara
2021-05-12 14:40 ` Matthew Wilcox [this message]
2021-05-13 19:01 ` Jan Kara
2021-05-13 19:38 ` Matthew Wilcox
2021-05-14 11:07 ` Jan Kara
2021-05-12 15:23 ` Darrick J. Wong
2021-05-13 17:44 ` Jan Kara
2021-05-13 18:52 ` Darrick J. Wong
2021-05-13 23:19 ` Dave Chinner
2021-05-14 16:17 ` Darrick J. Wong
2021-05-17 11:21 ` Jan Kara
2021-05-18 22:36 ` Dave Chinner
2021-05-19 10:57 ` Jan Kara
2021-05-12 13:46 ` [PATCH 04/11] ext4: Convert to use mapping->invalidate_lock Jan Kara
2021-05-12 13:46 ` [PATCH 05/11] ext2: Convert to using invalidate_lock Jan Kara
2021-05-12 13:46 ` [PATCH 06/11] xfs: Convert to use invalidate_lock Jan Kara
2021-05-12 13:46 ` [PATCH 07/11] zonefs: Convert to using invalidate_lock Jan Kara
2021-05-13 0:34 ` Damien Le Moal
2021-05-12 13:46 ` [PATCH 08/11] f2fs: " Jan Kara
2021-05-12 13:46 ` [PATCH 09/11] fuse: " Jan Kara
2021-05-12 13:46 ` [PATCH 10/11] ceph: Fix race between hole punch and page fault Jan Kara
2021-05-12 15:19 ` Jeff Layton
2021-05-12 13:46 ` [PATCH 11/11] cifs: " Jan Kara
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