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From: Matthew Wilcox <willy@infradead.org>
To: David Howells <dhowells@redhat.com>
Cc: Trond Myklebust <trondmy@hammerspace.com>,
	Anna Schumaker <anna.schumaker@netapp.com>,
	Steve French <sfrench@samba.org>,
	Dominique Martinet <asmadeus@codewreck.org>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Christoph Hellwig <hch@lst.de>,
	Alexander Viro <viro@zeniv.linux.org.uk>,
	linux-mm@kvack.org, linux-cachefs@redhat.com,
	linux-afs@lists.infradead.org, linux-nfs@vger.kernel.org,
	linux-cifs@vger.kernel.org, ceph-devel@vger.kernel.org,
	v9fs-developer@lists.sourceforge.net,
	linux-fsdevel@vger.kernel.org, Jeff Layton <jlayton@redhat.com>,
	David Wysochanski <dwysocha@redhat.com>,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH v4 02/28] mm: Add an unlock function for PG_private_2/PG_fscache
Date: Tue, 23 Mar 2021 13:51:16 +0000	[thread overview]
Message-ID: <20210323135116.GF1719932@casper.infradead.org> (raw)
In-Reply-To: <2499407.1616505440@warthog.procyon.org.uk>

On Tue, Mar 23, 2021 at 01:17:20PM +0000, David Howells wrote:
> +++ b/fs/afs/write.c
> @@ -846,7 +846,7 @@ vm_fault_t afs_page_mkwrite(struct vm_fault *vmf)
>  	 */
>  #ifdef CONFIG_AFS_FSCACHE
>  	if (PageFsCache(page) &&
> -	    wait_on_page_bit_killable(page, PG_fscache) < 0)
> +	    wait_on_page_fscache_killable(page) < 0)
>  		return VM_FAULT_RETRY;
>  #endif
>  
> @@ -861,7 +861,8 @@ vm_fault_t afs_page_mkwrite(struct vm_fault *vmf)
>  	 * details the portion of the page we need to write back and we might
>  	 * need to redirty the page if there's a problem.
>  	 */
> -	wait_on_page_writeback(page);
> +	if (wait_on_page_writeback_killable(page) < 0)
> +		return VM_FAULT_RETRY | VM_FAULT_LOCKED;

You forgot to unlock the page.  Also, if you're waiting killably here,
do you need to wait before you get the page lock?  Ditto for waiting on
fscache -- do you want to do that before or after you get the page lock?

Also, I never quite understood why you needed to wait for fscache
writes to finish before allowing the page to be dirtied.  Is this a
wait_for_stable_page() kind of situation, where the cache might be
calculating a checksum on it?  Because as far as I can tell, once the
page is dirty in RAM, the contents of the on-disk cache are irrelevant ...
unless they're part of a RAID 5 checksum kind of situation.

I didn't spot any other problems ...

  reply	other threads:[~2021-03-23 13:53 UTC|newest]

Thread overview: 46+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-03-10 16:54 [PATCH v4 00/28] Network fs helper library & fscache kiocb API David Howells
2021-03-10 16:54 ` [PATCH v4 01/28] iov_iter: Add ITER_XARRAY David Howells
2021-03-10 16:54 ` [PATCH v4 02/28] mm: Add an unlock function for PG_private_2/PG_fscache David Howells
2021-03-16 19:07   ` Matthew Wilcox
2021-03-17  0:43     ` Linus Torvalds
2021-03-17  2:12       ` Josef Bacik
2021-03-17  2:35         ` Linus Torvalds
2021-03-17  9:04         ` David Howells
2021-03-17 10:53         ` David Howells
2021-03-16 20:38   ` David Howells
2021-03-16 23:32     ` Matthew Wilcox
2021-03-21 10:53   ` Matthew Wilcox
2021-03-22 10:56   ` David Howells
2021-03-23 13:17   ` David Howells
2021-03-23 13:51     ` Matthew Wilcox [this message]
2021-03-23 14:16     ` David Howells
2021-03-23 22:06     ` David Howells
2021-03-10 16:55 ` [PATCH v4 03/28] mm: Implement readahead_control pageset expansion David Howells
2021-03-10 16:55 ` [PATCH v4 04/28] netfs: Make a netfs helper module David Howells
2021-03-10 16:55 ` [PATCH v4 05/28] netfs: Documentation for helper library David Howells
2021-03-10 16:55 ` [PATCH v4 06/28] netfs, mm: Move PG_fscache helper funcs to linux/netfs.h David Howells
2021-03-10 16:56 ` [PATCH v4 07/28] netfs, mm: Add unlock_page_fscache() and wait_on_page_fscache() David Howells
2021-03-10 16:56 ` [PATCH v4 08/28] netfs: Provide readahead and readpage netfs helpers David Howells
2021-03-21  1:42   ` Matthew Wilcox
2021-03-22 17:13   ` David Howells
2021-03-10 16:56 ` [PATCH v4 09/28] netfs: Add tracepoints David Howells
2021-03-10 16:56 ` [PATCH v4 10/28] netfs: Gather stats David Howells
2021-03-10 16:56 ` [PATCH v4 11/28] netfs: Add write_begin helper David Howells
2021-03-10 16:57 ` [PATCH v4 12/28] netfs: Define an interface to talk to a cache David Howells
2021-03-10 16:57 ` [PATCH v4 13/28] netfs: Hold a ref on a page when PG_private_2 is set David Howells
2021-03-10 16:57 ` [PATCH v4 14/28] fscache, cachefiles: Add alternate API to use kiocb for read/write to cache David Howells
2021-03-10 16:57 ` [PATCH v4 15/28] afs: Disable use of the fscache I/O routines David Howells
2021-03-10 16:58 ` [PATCH v4 16/28] afs: Pass page into dirty region helpers to provide THP size David Howells
2021-03-10 16:58 ` [PATCH v4 17/28] afs: Print the operation debug_id when logging an unexpected data version David Howells
2021-03-10 16:58 ` [PATCH v4 18/28] afs: Move key to afs_read struct David Howells
2021-03-10 16:58 ` [PATCH v4 19/28] afs: Don't truncate iter during data fetch David Howells
2021-03-10 16:58 ` [PATCH v4 20/28] afs: Log remote unmarshalling errors David Howells
2021-03-10 16:59 ` [PATCH v4 21/28] afs: Set up the iov_iter before calling afs_extract_data() David Howells
2021-03-10 16:59 ` [PATCH v4 22/28] afs: Use ITER_XARRAY for writing David Howells
2021-03-10 16:59 ` [PATCH v4 23/28] afs: Wait on PG_fscache before modifying/releasing a page David Howells
2021-03-10 16:59 ` [PATCH v4 24/28] afs: Extract writeback extension into its own function David Howells
2021-03-10 16:59 ` [PATCH v4 25/28] afs: Prepare for use of THPs David Howells
2021-03-10 17:00 ` [PATCH v4 26/28] afs: Use the fs operation ops to handle FetchData completion David Howells
2021-03-10 17:00 ` [PATCH v4 27/28] afs: Use new fscache read helper API David Howells
2021-03-10 17:00 ` [PATCH v4 28/28] afs: Use the fscache_write_begin() helper David Howells
2021-03-16 11:34 ` [PATCH v4 08/28] netfs: Provide readahead and readpage netfs helpers David Howells

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