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>

20 files changed, 21 insertions, 2 deletions

diff --git a/arch/arm/mm/fault.c b/arch/arm/mm/fault.c
index c3bd8345022..5dbf13f954f 100644
--- a/arch/arm/mm/fault.c
+++ b/arch/arm/mm/fault.c
@@ -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;
                 }
         }
diff --git a/arch/avr32/mm/fault.c b/arch/avr32/mm/fault.c
index b92e6095861..b2f2d2d6684 100644
--- a/arch/avr32/mm/fault.c
+++ b/arch/avr32/mm/fault.c
@@ -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
diff --git a/arch/cris/mm/fault.c b/arch/cris/mm/fault.c
index 45fd542cf17..73312ab6c69 100644
--- a/arch/cris/mm/fault.c
+++ b/arch/cris/mm/fault.c
@@ -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
diff --git a/arch/hexagon/mm/vm_fault.c b/arch/hexagon/mm/vm_fault.c
index 06695cc4fe5..513b74cb397 100644
--- a/arch/hexagon/mm/vm_fault.c
+++ b/arch/hexagon/mm/vm_fault.c
@@ -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;
                         }
                 }
diff --git a/arch/ia64/mm/fault.c b/arch/ia64/mm/fault.c
index 8443daf4f51..6cf0341f978 100644
--- a/arch/ia64/mm/fault.c
+++ b/arch/ia64/mm/fault.c
@@ -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
diff --git a/arch/m68k/mm/fault.c b/arch/m68k/mm/fault.c
index aeebbb7b30f..a563727806b 100644
--- a/arch/m68k/mm/fault.c
+++ b/arch/m68k/mm/fault.c
@@ -170,6 +170,7 @@ good_area:
                         /* Clear FAULT_FLAG_ALLOW_RETRY to avoid any risk
                          * of starvation. */
                         flags &= ~FAULT_FLAG_ALLOW_RETRY;
+                        flags |= FAULT_FLAG_TRIED;
 
                         /*
                          * No need to up_read(&mm->mmap_sem) as we would
diff --git a/arch/microblaze/mm/fault.c b/arch/microblaze/mm/fault.c
index eb365d6795f..714b35a9c4f 100644
--- a/arch/microblaze/mm/fault.c
+++ b/arch/microblaze/mm/fault.c
@@ -233,6 +233,7 @@ good_area:
                         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
diff --git a/arch/mips/mm/fault.c b/arch/mips/mm/fault.c
index c14f6dfed99..9f513486af1 100644
--- a/arch/mips/mm/fault.c
+++ b/arch/mips/mm/fault.c
@@ -171,6 +171,7 @@ good_area:
                 }
                 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
diff --git a/arch/openrisc/mm/fault.c b/arch/openrisc/mm/fault.c
index 40f850e9766..e2bfafce66c 100644
--- a/arch/openrisc/mm/fault.c
+++ b/arch/openrisc/mm/fault.c
@@ -183,6 +183,7 @@ 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 already released it in __lock_page_or_retry
diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c
index 5495ebe983a..0a6b28336eb 100644
--- a/arch/powerpc/mm/fault.c
+++ b/arch/powerpc/mm/fault.c
@@ -451,6 +451,7 @@ good_area:
                         /* Clear FAULT_FLAG_ALLOW_RETRY to avoid any risk
                          * of starvation. */
                         flags &= ~FAULT_FLAG_ALLOW_RETRY;
+                        flags |= FAULT_FLAG_TRIED;
                         goto retry;
                 }
         }
diff --git a/arch/s390/mm/fault.c b/arch/s390/mm/fault.c
index ac9122ca115..04ad4001a28 100644
--- a/arch/s390/mm/fault.c
+++ b/arch/s390/mm/fault.c
@@ -367,6 +367,7 @@ retry:
                         /* Clear FAULT_FLAG_ALLOW_RETRY to avoid any risk
                          * of starvation. */
                         flags &= ~FAULT_FLAG_ALLOW_RETRY;
+                        flags |= FAULT_FLAG_TRIED;
                         down_read(&mm->mmap_sem);
                         goto retry;
                 }
diff --git a/arch/sh/mm/fault.c b/arch/sh/mm/fault.c
index 3bdc1ad9a34..cbbdcad8fcb 100644
--- a/arch/sh/mm/fault.c
+++ b/arch/sh/mm/fault.c
@@ -504,6 +504,7 @@ good_area:
                 }
                 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
diff --git a/arch/sparc/mm/fault_32.c b/arch/sparc/mm/fault_32.c
index 77ac917be15..e98bfda205a 100644
--- a/arch/sparc/mm/fault_32.c
+++ b/arch/sparc/mm/fault_32.c
@@ -265,6 +265,7 @@ good_area:
                 }
                 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
diff --git a/arch/sparc/mm/fault_64.c b/arch/sparc/mm/fault_64.c
index 1fe0429b631..413d2926330 100644
--- a/arch/sparc/mm/fault_64.c
+++ b/arch/sparc/mm/fault_64.c
@@ -452,6 +452,7 @@ good_area:
                 }
                 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
diff --git a/arch/tile/mm/fault.c b/arch/tile/mm/fault.c
index 84ce7abbf5a..fe811fa5f1b 100644
--- a/arch/tile/mm/fault.c
+++ b/arch/tile/mm/fault.c
@@ -454,6 +454,7 @@ 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
diff --git a/arch/um/kernel/trap.c b/arch/um/kernel/trap.c
index 0353b98ae35..0f00e9c8208 100644
--- a/arch/um/kernel/trap.c
+++ b/arch/um/kernel/trap.c
@@ -89,6 +89,7 @@ good_area:
                                 current->min_flt++;
                         if (fault & VM_FAULT_RETRY) {
                                 flags &= ~FAULT_FLAG_ALLOW_RETRY;
+                                flags |= FAULT_FLAG_TRIED;
 
                                 goto retry;
                         }
diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index a530b230e7d..8e13ecb41be 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -1220,6 +1220,7 @@ good_area:
                         /* Clear FAULT_FLAG_ALLOW_RETRY to avoid any risk
                          * of starvation. */
                         flags &= ~FAULT_FLAG_ALLOW_RETRY;
+                        flags |= FAULT_FLAG_TRIED;
                         goto retry;
                 }
         }
diff --git a/arch/xtensa/mm/fault.c b/arch/xtensa/mm/fault.c
index 5a74c53bc69..2c2f710ed1d 100644
--- a/arch/xtensa/mm/fault.c
+++ b/arch/xtensa/mm/fault.c
@@ -126,6 +126,7 @@ good_area:
                         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
diff --git a/include/linux/mm.h b/include/linux/mm.h
index b01e585ab4b..bcaab4e6fe9 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -161,6 +161,7 @@ extern pgprot_t protection_map[16];
 #define FAULT_FLAG_ALLOW_RETRY  0x08    /* Retry fault if blocking */
 #define FAULT_FLAG_RETRY_NOWAIT 0x10    /* Don't drop mmap_sem and wait when retrying */
 #define FAULT_FLAG_KILLABLE     0x20    /* The fault task is in SIGKILL killable region */
+#define FAULT_FLAG_TRIED        0x40    /* second try */
 
 /*
  * vm_fault is filled by the the pagefault handler and passed to the vma's
diff --git a/mm/filemap.c b/mm/filemap.c
index a9827b42556..83efee76a5c 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -1607,13 +1607,13 @@ int filemap_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
          * Do we have something in the page cache already?
          */
         page = find_get_page(mapping, offset);
-        if (likely(page)) {
+        if (likely(page) && !(vmf->flags & FAULT_FLAG_TRIED)) {
                 /*
                  * We found the page, so try async readahead before
                  * waiting for the lock.
                  */
                 do_async_mmap_readahead(vma, ra, file, page, offset);
-        } else {
+        } else if (!page) {
                 /* No page in the page cache at all */
                 do_sync_mmap_readahead(vma, ra, file, offset);
                 count_vm_event(PGMAJFAULT);