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Commit 45cac65b authored Oct 08, 2012 by Shaohua Li Committed by Linus Torvalds Oct 09, 2012

readahead: fault retry breaks mmap file read random detection



.fault now can retry.  The retry can break state machine of .fault.  In
filemap_fault, if page is miss, ra->mmap_miss is increased.  In the second
try, since the page is in page cache now, ra->mmap_miss is decreased.  And
these are done in one fault, so we can't detect random mmap file access.

Add a new flag to indicate .fault is tried once.  In the second try, skip
ra->mmap_miss decreasing.  The filemap_fault state machine is ok with it.

I only tested x86, didn't test other archs, but looks the change for other
archs is obvious, but who knows :)

Signed-off-by: Shaohua Li <shaohua.li@fusionio.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Wu Fengguang <fengguang.wu@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent e79bee24

arch/arm/mm/fault.c

+1 −0

Original line number	Diff line number	Diff line
		@@ -336,6 +336,7 @@ do_page_fault(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
		/* Clear FAULT_FLAG_ALLOW_RETRY to avoid any risk
		* of starvation. */
		flags &= ~FAULT_FLAG_ALLOW_RETRY;
		flags \|= FAULT_FLAG_TRIED;
		goto retry;
		}
		}

arch/avr32/mm/fault.c

+1 −0

Original line number	Diff line number	Diff line
		@@ -152,6 +152,7 @@ asmlinkage void do_page_fault(unsigned long ecr, struct pt_regs *regs)
		tsk->min_flt++;
		if (fault & VM_FAULT_RETRY) {
		flags &= ~FAULT_FLAG_ALLOW_RETRY;
		flags \|= FAULT_FLAG_TRIED;

		/*
		* No need to up_read(&mm->mmap_sem) as we would have

arch/cris/mm/fault.c

+1 −0

Original line number	Diff line number	Diff line
		@@ -186,6 +186,7 @@ do_page_fault(unsigned long address, struct pt_regs *regs,
		tsk->min_flt++;
		if (fault & VM_FAULT_RETRY) {
		flags &= ~FAULT_FLAG_ALLOW_RETRY;
		flags \|= FAULT_FLAG_TRIED;

		/*
		* No need to up_read(&mm->mmap_sem) as we would

arch/hexagon/mm/vm_fault.c

+1 −0

Original line number	Diff line number	Diff line
		@@ -113,6 +113,7 @@ void do_page_fault(unsigned long address, long cause, struct pt_regs *regs)
		current->min_flt++;
		if (fault & VM_FAULT_RETRY) {
		flags &= ~FAULT_FLAG_ALLOW_RETRY;
		flags \|= FAULT_FLAG_TRIED;
		goto retry;
		}
		}

arch/ia64/mm/fault.c

+1 −0

Original line number	Diff line number	Diff line
		@@ -184,6 +184,7 @@ ia64_do_page_fault (unsigned long address, unsigned long isr, struct pt_regs *re
		current->min_flt++;
		if (fault & VM_FAULT_RETRY) {
		flags &= ~FAULT_FLAG_ALLOW_RETRY;
		flags \|= FAULT_FLAG_TRIED;

		/* No need to up_read(&mm->mmap_sem) as we would
		* have already released it in __lock_page_or_retry