readahead: fault retry breaks mmap file read random detection
Shaohua Li [Mon, 8 Oct 2012 23:32:19 +0000 (16:32 -0700)]
.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:
arch/arm/mm/fault.c
arch/avr32/mm/fault.c
arch/cris/mm/fault.c
arch/hexagon/mm/vm_fault.c
arch/ia64/mm/fault.c
arch/m68k/mm/fault.c
arch/microblaze/mm/fault.c
arch/mips/mm/fault.c
arch/openrisc/mm/fault.c
arch/powerpc/mm/fault.c
arch/s390/mm/fault.c
arch/sh/mm/fault.c
arch/sparc/mm/fault_32.c
arch/sparc/mm/fault_64.c
arch/tile/mm/fault.c
arch/um/kernel/trap.c
arch/x86/mm/fault.c
arch/xtensa/mm/fault.c
include/linux/mm.h
mm/filemap.c

index c3bd834..5dbf13f 100644 (file)
@@ -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;
                }
        }
index b92e609..b2f2d2d 100644 (file)
@@ -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
index 45fd542..73312ab 100644 (file)
@@ -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
index 06695cc..513b74c 100644 (file)
@@ -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;
                        }
                }
index 8443daf..6cf0341 100644 (file)
@@ -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
index aeebbb7..a563727 100644 (file)
@@ -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
index eb365d6..714b35a 100644 (file)
@@ -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
index c14f6df..9f51348 100644 (file)
@@ -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
index 40f850e..e2bfafc 100644 (file)
@@ -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
index 5495ebe..0a6b283 100644 (file)
@@ -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;
                }
        }
index ac9122c..04ad400 100644 (file)
@@ -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;
                }
index 3bdc1ad..cbbdcad 100644 (file)
@@ -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
index 77ac917..e98bfda 100644 (file)
@@ -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
index 1fe0429..413d292 100644 (file)
@@ -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
index 84ce7ab..fe811fa 100644 (file)
@@ -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
index 0353b98..0f00e9c 100644 (file)
@@ -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;
                        }
index a530b23..8e13ecb 100644 (file)
@@ -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;
                }
        }
index 5a74c53..2c2f710 100644 (file)
@@ -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
index b01e585..bcaab4e 100644 (file)
@@ -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
index a9827b4..83efee7 100644 (file)
@@ -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);