From: "Darrick J. Wong" <darrick.wong@oracle.com>
To: Matthew Wilcox <willy@infradead.org>
Cc: linux-fsdevel@vger.kernel.org, linux-mm@kvack.org,
linux-kernel@vger.kernel.org, linux-btrfs@vger.kernel.org,
linux-erofs@lists.ozlabs.org, linux-ext4@vger.kernel.org,
linux-f2fs-devel@lists.sourceforge.net, cluster-devel@redhat.com,
ocfs2-devel@oss.oracle.com, linux-xfs@vger.kernel.org
Subject: Re: [PATCH v7 21/24] iomap: Restructure iomap_readpages_actor
Date: Fri, 21 Feb 2020 16:44:25 -0800 [thread overview]
Message-ID: <20200222004425.GG9506@magnolia> (raw)
In-Reply-To: <20200219210103.32400-22-willy@infradead.org>
On Wed, Feb 19, 2020 at 01:01:00PM -0800, Matthew Wilcox wrote:
> From: "Matthew Wilcox (Oracle)" <willy@infradead.org>
>
> By putting the 'have we reached the end of the page' condition at the end
> of the loop instead of the beginning, we can remove the 'submit the last
> page' code from iomap_readpages(). Also check that iomap_readpage_actor()
> didn't return 0, which would lead to an endless loop.
>
> Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
> ---
> fs/iomap/buffered-io.c | 32 ++++++++++++++++++--------------
> 1 file changed, 18 insertions(+), 14 deletions(-)
>
> diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
> index cb3511eb152a..31899e6cb0f8 100644
> --- a/fs/iomap/buffered-io.c
> +++ b/fs/iomap/buffered-io.c
> @@ -400,15 +400,9 @@ iomap_readpages_actor(struct inode *inode, loff_t pos, loff_t length,
> void *data, struct iomap *iomap, struct iomap *srcmap)
> {
> struct iomap_readpage_ctx *ctx = data;
> - loff_t done, ret;
> -
> - for (done = 0; done < length; done += ret) {
> - if (ctx->cur_page && offset_in_page(pos + done) == 0) {
> - if (!ctx->cur_page_in_bio)
> - unlock_page(ctx->cur_page);
> - put_page(ctx->cur_page);
> - ctx->cur_page = NULL;
> - }
> + loff_t ret, done = 0;
> +
> + while (done < length) {
> if (!ctx->cur_page) {
> ctx->cur_page = iomap_next_page(inode, ctx->pages,
> pos, length, &done);
> @@ -418,6 +412,20 @@ iomap_readpages_actor(struct inode *inode, loff_t pos, loff_t length,
> }
> ret = iomap_readpage_actor(inode, pos + done, length - done,
> ctx, iomap, srcmap);
> + done += ret;
> +
> + /* Keep working on a partial page */
> + if (ret && offset_in_page(pos + done))
> + continue;
> +
> + if (!ctx->cur_page_in_bio)
> + unlock_page(ctx->cur_page);
> + put_page(ctx->cur_page);
> + ctx->cur_page = NULL;
> +
> + /* Don't loop forever if we made no progress */
> + if (WARN_ON(!ret))
> + break;
> }
>
> return done;
> @@ -451,11 +459,7 @@ iomap_readpages(struct address_space *mapping, struct list_head *pages,
> done:
> if (ctx.bio)
> submit_bio(ctx.bio);
> - if (ctx.cur_page) {
> - if (!ctx.cur_page_in_bio)
> - unlock_page(ctx.cur_page);
> - put_page(ctx.cur_page);
> - }
> + BUG_ON(ctx.cur_page);
Whoah, is the system totally unrecoverably hosed at this point?
I get that this /shouldn't/ happen, but should we somehow end up with a
page here, are we unable either to release it or even just leak it? I'd
have thought a WARN_ON would be just fine here.
--D
>
> /*
> * Check that we didn't lose a page due to the arcance calling
> --
> 2.25.0
>
next prev parent reply other threads:[~2020-02-22 0:45 UTC|newest]
Thread overview: 76+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-19 21:00 [PATCH v7 00/23] Change readahead API Matthew Wilcox
2020-02-19 21:00 ` [PATCH v7 01/24] mm: Move readahead prototypes from mm.h Matthew Wilcox
2020-02-21 2:43 ` John Hubbard
2020-02-21 21:48 ` Matthew Wilcox
2020-02-22 0:15 ` John Hubbard
2020-02-24 21:32 ` Christoph Hellwig
2020-02-19 21:00 ` [PATCH v7 02/24] mm: Return void from various readahead functions Matthew Wilcox
2020-02-24 21:33 ` Christoph Hellwig
2020-02-19 21:00 ` [PATCH v7 03/24] mm: Ignore return value of ->readpages Matthew Wilcox
2020-02-19 21:00 ` [PATCH v7 04/24] mm: Move readahead nr_pages check into read_pages Matthew Wilcox
2020-02-20 14:36 ` Zi Yan
2020-02-21 4:24 ` John Hubbard
2020-02-24 21:34 ` Christoph Hellwig
2020-02-19 21:00 ` [PATCH v7 05/24] mm: Use readahead_control to pass arguments Matthew Wilcox
2020-02-24 21:36 ` Christoph Hellwig
2020-02-19 21:00 ` [PATCH v7 06/24] mm: Rename various 'offset' parameters to 'index' Matthew Wilcox
2020-02-21 2:21 ` John Hubbard
2020-02-21 3:27 ` John Hubbard
2020-02-19 21:00 ` [PATCH v7 07/24] mm: rename readahead loop variable to 'i' Matthew Wilcox
2020-02-19 21:00 ` [PATCH v7 08/24] mm: Remove 'page_offset' from readahead loop Matthew Wilcox
2020-02-21 2:48 ` John Hubbard
2020-02-24 21:37 ` Christoph Hellwig
2020-02-19 21:00 ` [PATCH v7 09/24] mm: Put readahead pages in cache earlier Matthew Wilcox
2020-02-21 3:19 ` John Hubbard
2020-02-21 3:43 ` Matthew Wilcox
2020-02-21 4:19 ` John Hubbard
2020-02-24 21:40 ` Christoph Hellwig
2020-02-19 21:00 ` [PATCH v7 10/24] mm: Add readahead address space operation Matthew Wilcox
2020-02-20 15:00 ` Zi Yan
2020-02-20 15:10 ` Matthew Wilcox
2020-02-21 4:30 ` John Hubbard
2020-02-24 21:41 ` Christoph Hellwig
2020-02-19 21:00 ` [PATCH v7 11/24] mm: Move end_index check out of readahead loop Matthew Wilcox
2020-02-21 3:50 ` John Hubbard
2020-02-21 15:35 ` Matthew Wilcox
2020-02-21 19:41 ` John Hubbard
2020-02-19 21:00 ` [PATCH v7 12/24] mm: Add page_cache_readahead_unbounded Matthew Wilcox
2020-02-24 21:53 ` [Cluster-devel] " Christoph Hellwig
2020-02-19 21:00 ` [PATCH v7 13/24] fs: Convert mpage_readpages to mpage_readahead Matthew Wilcox
2020-02-24 21:54 ` [Cluster-devel] " Christoph Hellwig
2020-02-19 21:00 ` [PATCH v7 14/24] btrfs: Convert from readpages to readahead Matthew Wilcox
2020-02-20 9:42 ` Johannes Thumshirn
2020-02-20 13:48 ` Matthew Wilcox
2020-02-20 15:46 ` Christoph Hellwig
2020-02-20 15:54 ` Matthew Wilcox
2020-02-20 15:57 ` Christoph Hellwig
2020-02-24 21:43 ` Christoph Hellwig
2020-02-24 21:54 ` Matthew Wilcox
2020-02-24 21:57 ` Christoph Hellwig
2020-02-19 21:00 ` [PATCH v7 15/24] erofs: Convert uncompressed files " Matthew Wilcox
2020-02-19 21:00 ` [PATCH v7 16/24] erofs: Convert compressed " Matthew Wilcox
2020-02-19 21:00 ` [PATCH v7 17/24] ext4: Convert " Matthew Wilcox
2020-02-19 21:00 ` [PATCH v7 18/24] ext4: Pass the inode to ext4_mpage_readpages Matthew Wilcox
2020-02-19 21:00 ` [PATCH v7 19/24] f2fs: Convert from readpages to readahead Matthew Wilcox
2020-02-19 21:00 ` [PATCH v7 20/24] fuse: " Matthew Wilcox
2020-02-19 21:01 ` [PATCH v7 21/24] iomap: Restructure iomap_readpages_actor Matthew Wilcox
2020-02-20 15:47 ` Christoph Hellwig
2020-02-20 16:24 ` Matthew Wilcox
2020-02-24 22:17 ` Christoph Hellwig
2020-02-25 1:49 ` Matthew Wilcox
2020-02-22 0:44 ` Darrick J. Wong [this message]
2020-02-22 1:54 ` Matthew Wilcox
2020-02-23 17:55 ` Darrick J. Wong
2020-02-19 21:01 ` [PATCH v7 22/24] iomap: Convert from readpages to readahead Matthew Wilcox
2020-02-20 15:49 ` Christoph Hellwig
2020-02-20 16:57 ` Matthew Wilcox
2020-02-22 1:00 ` Darrick J. Wong
2020-02-24 4:33 ` Matthew Wilcox
2020-02-24 16:52 ` Darrick J. Wong
2020-02-22 1:03 ` Darrick J. Wong
2020-02-22 1:09 ` Matthew Wilcox
2020-02-19 21:01 ` [PATCH v7 23/24] mm: Document why we don't set PageReadahead Matthew Wilcox
2020-02-19 21:01 ` [PATCH v7 24/24] mm: Use memalloc_nofs_save in readahead path Matthew Wilcox
2020-02-20 17:54 ` [PATCH v7 00/23] Change readahead API David Sterba
2020-02-20 22:39 ` Matthew Wilcox
2020-02-21 11:59 ` David Sterba
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