readahead: fault retry breaks mmap file read random detection (45cac65b) · Commits · 戴 / test

.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>

arch/arm/mm/fault.c

+1 −0

Original line number	Diff line number	Diff line
		@@ -336,6 +336,7 @@ retry:
		/* 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 @@ good_area:
		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 @@ retry:
		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 @@ good_area:
		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 @@ retry:
		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

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