From: Nick Piggin <nickpiggin@yahoo.com.au> To: Andrew Morton <akpm@linux-foundation.org> Cc: Nick Piggin <npiggin@suse.de>, Linus Torvalds <torvalds@linux-foundation.org>, Hugh Dickins <hugh@veritas.com>, Linux Kernel <linux-kernel@vger.kernel.org>, Linux Memory Management <linux-mm@kvack.org>, Linux Filesystems <linux-fsdevel@vger.kernel.org> Subject: Re: [patch 1/3] mm: fix PageUptodate memorder Date: Tue, 06 Feb 2007 19:51:49 +1100 [thread overview] Message-ID: <45C841A5.20702@yahoo.com.au> (raw) In-Reply-To: <20070206002512.4e0bbbad.akpm@linux-foundation.org> Andrew Morton wrote: > On Tue, 6 Feb 2007 09:02:11 +0100 (CET) Nick Piggin <npiggin@suse.de> wrote: > > >>+static inline void __SetPageUptodate(struct page *page) >>+{ >>+#ifdef CONFIG_S390 >> if (!test_and_set_bit(PG_uptodate, &page->flags)) >> page_test_and_clear_dirty(page); >>-} >> #else >>-#define SetPageUptodate(page) set_bit(PG_uptodate, &(page)->flags) >>+ /* >>+ * Memory barrier must be issued before setting the PG_uptodate bit, >>+ * so all previous writes that served to bring the page uptodate are >>+ * visible before PageUptodate becomes true. >>+ * >>+ * S390 is guaranteed to have a barrier in the test_and_set operation >>+ * (see Documentation/atomic_ops.txt). >>+ * >>+ * XXX: does this memory barrier need to be anything special to >>+ * handle things like DMA writes into the page? >>+ */ >>+ smp_wmb(); >>+ set_bit(PG_uptodate, &(page)->flags); >> #endif >>+} >>+ >>+static inline void SetPageUptodate(struct page *page) >>+{ >>+ WARN_ON(!PageLocked(page)); >>+ __SetPageUptodate(page); >>+} >>+ >>+static inline void SetNewPageUptodate(struct page *page) >>+{ >>+ __SetPageUptodate(page); >>+} > > > I was panicing for a minute when I saw that __SetPageUptodate() in there. > > Conventionally the __SetPageFoo namespace is for nonatomic updates to > page->flags. Can we call this something different? Duh, of course, sorry. > What a fugly patchset :( Fugly problem. One could fix it by always locking the page, but I was worried about Hugh flaming me if I tried that ;) -- SUSE Labs, Novell Inc. Send instant messages to your online friends http://au.messenger.yahoo.com
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From: Nick Piggin <nickpiggin@yahoo.com.au> To: Andrew Morton <akpm@linux-foundation.org> Cc: Nick Piggin <npiggin@suse.de>, Linus Torvalds <torvalds@linux-foundation.org>, Hugh Dickins <hugh@veritas.com>, Linux Kernel <linux-kernel@vger.kernel.org>, Linux Memory Management <linux-mm@kvack.org>, Linux Filesystems <linux-fsdevel@vger.kernel.org> Subject: Re: [patch 1/3] mm: fix PageUptodate memorder Date: Tue, 06 Feb 2007 19:51:49 +1100 [thread overview] Message-ID: <45C841A5.20702@yahoo.com.au> (raw) In-Reply-To: <20070206002512.4e0bbbad.akpm@linux-foundation.org> Andrew Morton wrote: > On Tue, 6 Feb 2007 09:02:11 +0100 (CET) Nick Piggin <npiggin@suse.de> wrote: > > >>+static inline void __SetPageUptodate(struct page *page) >>+{ >>+#ifdef CONFIG_S390 >> if (!test_and_set_bit(PG_uptodate, &page->flags)) >> page_test_and_clear_dirty(page); >>-} >> #else >>-#define SetPageUptodate(page) set_bit(PG_uptodate, &(page)->flags) >>+ /* >>+ * Memory barrier must be issued before setting the PG_uptodate bit, >>+ * so all previous writes that served to bring the page uptodate are >>+ * visible before PageUptodate becomes true. >>+ * >>+ * S390 is guaranteed to have a barrier in the test_and_set operation >>+ * (see Documentation/atomic_ops.txt). >>+ * >>+ * XXX: does this memory barrier need to be anything special to >>+ * handle things like DMA writes into the page? >>+ */ >>+ smp_wmb(); >>+ set_bit(PG_uptodate, &(page)->flags); >> #endif >>+} >>+ >>+static inline void SetPageUptodate(struct page *page) >>+{ >>+ WARN_ON(!PageLocked(page)); >>+ __SetPageUptodate(page); >>+} >>+ >>+static inline void SetNewPageUptodate(struct page *page) >>+{ >>+ __SetPageUptodate(page); >>+} > > > I was panicing for a minute when I saw that __SetPageUptodate() in there. > > Conventionally the __SetPageFoo namespace is for nonatomic updates to > page->flags. Can we call this something different? Duh, of course, sorry. > What a fugly patchset :( Fugly problem. One could fix it by always locking the page, but I was worried about Hugh flaming me if I tried that ;) -- SUSE Labs, Novell Inc. Send instant messages to your online friends http://au.messenger.yahoo.com -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
next prev parent reply other threads:[~2007-02-06 9:35 UTC|newest] Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top 2007-02-06 8:02 [patch 0/3] 2.6.20 fix for PageUptodate memorder problem Nick Piggin 2007-02-06 8:02 ` Nick Piggin 2007-02-06 8:02 ` [patch 1/3] mm: fix PageUptodate memorder Nick Piggin 2007-02-06 8:02 ` Nick Piggin 2007-02-06 8:25 ` Andrew Morton 2007-02-06 8:25 ` Andrew Morton 2007-02-06 8:51 ` Nick Piggin [this message] 2007-02-06 8:51 ` Nick Piggin 2007-02-06 8:02 ` [patch 2/3] fs: buffer don't PageUptodate without page locked Nick Piggin 2007-02-06 8:02 ` Nick Piggin 2007-02-06 8:21 ` Andrew Morton 2007-02-06 8:21 ` Andrew Morton 2007-02-06 8:31 ` Nick Piggin 2007-02-06 8:31 ` Nick Piggin 2007-02-06 8:02 ` [patch 3/3] mm: make read_cache_page synchronous Nick Piggin 2007-02-06 8:02 ` Nick Piggin 2007-02-06 8:28 ` Andrew Morton 2007-02-06 8:28 ` Andrew Morton 2007-02-06 8:56 ` Nick Piggin 2007-02-06 8:56 ` Nick Piggin 2007-02-06 8:58 ` Nick Piggin 2007-02-06 8:58 ` Nick Piggin 2007-02-06 22:58 ` [patch 0/3] 2.6.20 fix for PageUptodate memorder problem David Chinner 2007-02-06 22:58 ` David Chinner 2007-02-07 3:13 ` Nick Piggin 2007-02-07 3:13 ` Nick Piggin 2007-02-08 13:26 [patch 0/3] 2.6.20 fix for PageUptodate memorder problem (try 2) Nick Piggin 2007-02-08 13:27 ` [patch 1/3] mm: fix PageUptodate memorder Nick Piggin 2007-02-08 13:27 ` Nick Piggin
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