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Subject[PATCH 16/20 v2] tile/mm/fault.c: Port OOM changes to handle_page_fault
Date
Commit d065bd810b6deb67d4897a14bfe21f8eb526ba99
(mm: retry page fault when blocking on disk transfer) and
commit 37b23e0525d393d48a7d59f870b3bc061a30ccdb
(x86,mm: make pagefault killable)

The above commits introduced changes into the x86 pagefault handler
for making the page fault handler retryable as well as killable.

These changes reduce the mmap_sem hold time, which is crucial
during OOM killer invocation.

Port these changes to tile.

Signed-off-by: Kautuk Consul <consul.kautuk@gmail.com>
---
arch/tile/mm/fault.c | 31 ++++++++++++++++++++++++++-----
1 files changed, 26 insertions(+), 5 deletions(-)

diff --git a/arch/tile/mm/fault.c b/arch/tile/mm/fault.c
index c1eaaa1..a097631 100644
--- a/arch/tile/mm/fault.c
+++ b/arch/tile/mm/fault.c
@@ -267,6 +267,8 @@ static int handle_page_fault(struct pt_regs *regs,
int si_code;
int is_kernel_mode;
pgd_t *pgd;
+ unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE |
+ (write ? FAULT_FLAG_WRITE : 0);

/* on TILE, protection faults are always writes */
if (!is_page_fault)
@@ -373,6 +375,8 @@ static int handle_page_fault(struct pt_regs *regs,
vma = NULL; /* happy compiler */
goto bad_area_nosemaphore;
}
+
+retry:
down_read(&mm->mmap_sem);
}

@@ -420,7 +424,11 @@ good_area:
* make sure we exit gracefully rather than endlessly redo
* the fault.
*/
- fault = handle_mm_fault(mm, vma, address, write);
+ fault = handle_mm_fault(mm, vma, address, flags);
+
+ if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current))
+ return 0;
+
if (unlikely(fault & VM_FAULT_ERROR)) {
if (fault & VM_FAULT_OOM)
goto out_of_memory;
@@ -428,10 +436,23 @@ good_area:
goto do_sigbus;
BUG();
}
- if (fault & VM_FAULT_MAJOR)
- tsk->maj_flt++;
- else
- tsk->min_flt++;
+ if (flags & FAULT_FLAG_ALLOW_RETRY) {
+ if (fault & VM_FAULT_MAJOR)
+ tsk->maj_flt++;
+ else
+ tsk->min_flt++;
+ if (fault & VM_FAULT_RETRY) {
+ flags &= ~FAULT_FLAG_ALLOW_RETRY;
+
+ /*
+ * No need to up_read(&mm->mmap_sem) as we would
+ * have already released it in __lock_page_or_retry
+ * in mm/filemap.c.
+ */
+
+ goto retry;
+ }
+ }

#if CHIP_HAS_TILE_DMA() || CHIP_HAS_SN_PROC()
/*
--
1.7.5.4


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