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Date: Tue, 25 Aug 2020 14:02:03 -0700 From: "Darrick J. Wong" <darrick.wong@...cle.com> To: "Matthew Wilcox (Oracle)" <willy@...radead.org> Cc: linux-xfs@...r.kernel.org, linux-fsdevel@...r.kernel.org, linux-nvdimm@...ts.01.org, linux-kernel@...r.kernel.org Subject: Re: [PATCH 5/9] iomap: Support arbitrarily many blocks per page On Mon, Aug 24, 2020 at 03:55:06PM +0100, Matthew Wilcox (Oracle) wrote: > Size the uptodate array dynamically to support larger pages in the > page cache. With a 64kB page, we're only saving 8 bytes per page today, > but with a 2MB maximum page size, we'd have to allocate more than 4kB > per page. Add a few debugging assertions. > > Signed-off-by: Matthew Wilcox (Oracle) <willy@...radead.org> > --- > fs/iomap/buffered-io.c | 14 ++++++++++---- > 1 file changed, 10 insertions(+), 4 deletions(-) > > diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c > index dbf9572dabe9..844e95cacea8 100644 > --- a/fs/iomap/buffered-io.c > +++ b/fs/iomap/buffered-io.c > @@ -22,18 +22,19 @@ > #include "../internal.h" > > /* > - * Structure allocated for each page when block size < PAGE_SIZE to track > + * Structure allocated for each page when block size < page size to track > * sub-page uptodate status and I/O completions. "for each regular page or head page of a huge page"? Or whatever we're calling them nowadays? --D > */ > struct iomap_page { > atomic_t read_count; > atomic_t write_count; > spinlock_t uptodate_lock; > - DECLARE_BITMAP(uptodate, PAGE_SIZE / 512); > + unsigned long uptodate[]; > }; > > static inline struct iomap_page *to_iomap_page(struct page *page) > { > + VM_BUG_ON_PGFLAGS(PageTail(page), page); > if (page_has_private(page)) > return (struct iomap_page *)page_private(page); > return NULL; > @@ -45,11 +46,13 @@ static struct iomap_page * > iomap_page_create(struct inode *inode, struct page *page) > { > struct iomap_page *iop = to_iomap_page(page); > + unsigned int nr_blocks = i_blocks_per_page(inode, page); > > - if (iop || i_blocks_per_page(inode, page) <= 1) > + if (iop || nr_blocks <= 1) > return iop; > > - iop = kzalloc(sizeof(*iop), GFP_NOFS | __GFP_NOFAIL); > + iop = kzalloc(struct_size(iop, uptodate, BITS_TO_LONGS(nr_blocks)), > + GFP_NOFS | __GFP_NOFAIL); > spin_lock_init(&iop->uptodate_lock); > attach_page_private(page, iop); > return iop; > @@ -59,11 +62,14 @@ static void > iomap_page_release(struct page *page) > { > struct iomap_page *iop = detach_page_private(page); > + unsigned int nr_blocks = i_blocks_per_page(page->mapping->host, page); > > if (!iop) > return; > WARN_ON_ONCE(atomic_read(&iop->read_count)); > WARN_ON_ONCE(atomic_read(&iop->write_count)); > + WARN_ON_ONCE(bitmap_full(iop->uptodate, nr_blocks) != > + PageUptodate(page)); > kfree(iop); > } > > -- > 2.28.0 >
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