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 ...
next prev parent reply other threads:[~2021-03-23 13:51 UTC|newest]
Thread overview: 30+ 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 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
2021-03-16 11:34 ` [PATCH v4 08/28] netfs: Provide readahead and readpage netfs helpers David Howells
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