The return codes from fault handling functions are open-coded in
memory.c and arch/i386/mm/fault.c.
This patch removes them in favor of defining integer constants with
mnemonic names and using them as the return codes and in dispatches
on the return values from handle_mm_fault(), and also removing some of
the associated comments explaining what the magic numbers mean at
various points where they were formerly used. In addition two redundant
variables were removed, a comment was added to the bad_wp_page: label
to explain to onlookers more of what the printk() there means, and
failure to match the return code with a value in the various switch()
statements on the return code was flagged as a BUG() at various points.
>From what I saw in page_alloc.c last time, since these hit the same
lines, they might as well all go out in one batch. I am, of course,
willing to adjust/separate various bits as desired.
Cheers,
Bill
===== include/linux/mm.h 1.55 vs edited =====
--- 1.55/include/linux/mm.h Sat May 25 16:25:47 2002
+++ edited/include/linux/mm.h Fri Jun 7 15:59:07 2002
@@ -305,6 +305,16 @@
#define NOPAGE_SIGBUS (NULL)
#define NOPAGE_OOM ((struct page *) (-1))
+/*
+ * Different kinds of faults, as returned by handle_mm_fault().
+ * Used to decide whether a process gets delivered SIGBUS or
+ * just gets major/minor fault counters bumped up.
+ */
+#define VM_FAULT_OOM (-1)
+#define VM_FAULT_SIGBUS 0
+#define VM_FAULT_MINOR 1
+#define VM_FAULT_MAJOR 2
+
/* The array of struct pages */
extern struct page *mem_map;
===== mm/memory.c 1.70 vs edited =====
--- 1.70/mm/memory.c Fri May 31 18:18:07 2002
+++ edited/mm/memory.c Fri Jun 7 15:19:49 2002
@@ -514,18 +514,18 @@
while (!(map = follow_page(mm, start, write))) {
spin_unlock(&mm->page_table_lock);
switch (handle_mm_fault(mm, vma, start, write)) {
- case 1:
+ case VM_FAULT_MINOR:
tsk->min_flt++;
break;
- case 2:
+ case VM_FAULT_MAJOR:
tsk->maj_flt++;
break;
- case 0:
- if (i) return i;
- return -EFAULT;
+ case VM_FAULT_SIGBUS:
+ return i ? i : -EFAULT;
+ case VM_FAULT_OOM:
+ return i ? i : -ENOMEM;
default:
- if (i) return i;
- return -ENOMEM;
+ BUG();
}
spin_lock(&mm->page_table_lock);
}
@@ -982,7 +982,7 @@
establish_pte(vma, address, page_table, pte_mkyoung(pte_mkdirty(pte_mkwrite(pte))));
pte_unmap(page_table);
spin_unlock(&mm->page_table_lock);
- return 1; /* Minor fault */
+ return VM_FAULT_MINOR;
}
}
pte_unmap(page_table);
@@ -1016,16 +1016,21 @@
spin_unlock(&mm->page_table_lock);
page_cache_release(new_page);
page_cache_release(old_page);
- return 1; /* Minor fault */
+ return VM_FAULT_MINOR;
bad_wp_page:
pte_unmap(page_table);
spin_unlock(&mm->page_table_lock);
printk(KERN_ERR "do_wp_page: bogus page at address %08lx\n", address);
- return -1;
+ /*
+ * This should really halt the system so it can be debugged or
+ * at least the kernel stops what it's doing before it corrupts
+ * data, but for the moment just pretend this is OOM.
+ */
+ return VM_FAULT_OOM;
no_mem:
page_cache_release(old_page);
- return -1;
+ return VM_FAULT_OOM;
}
static void vmtruncate_list(list_t *head, unsigned long pgoff)
@@ -1149,7 +1154,7 @@
struct page *page;
swp_entry_t entry = pte_to_swp_entry(orig_pte);
pte_t pte;
- int ret = 1;
+ int ret = VM_FAULT_MINOR;
pte_unmap(page_table);
spin_unlock(&mm->page_table_lock);
@@ -1162,17 +1167,19 @@
* Back out if somebody else faulted in this pte while
* we released the page table lock.
*/
- int retval;
spin_lock(&mm->page_table_lock);
page_table = pte_offset_map(pmd, address);
- retval = pte_same(*page_table, orig_pte) ? -1 : 1;
+ if (pte_same(*page_table, orig_pte))
+ ret = VM_FAULT_OOM;
+ else
+ ret = VM_FAULT_MINOR;
pte_unmap(page_table);
spin_unlock(&mm->page_table_lock);
- return retval;
+ return ret;
}
/* Had to read the page from swap area: Major fault */
- ret = 2;
+ ret = VM_FAULT_MAJOR;
}
lock_page(page);
@@ -1188,7 +1195,7 @@
spin_unlock(&mm->page_table_lock);
unlock_page(page);
page_cache_release(page);
- return 1;
+ return VM_FAULT_MINOR;
}
/* The page isn't present yet, go ahead with the fault. */
@@ -1246,7 +1253,7 @@
pte_unmap(page_table);
page_cache_release(page);
spin_unlock(&mm->page_table_lock);
- return 1;
+ return VM_FAULT_MINOR;
}
mm->rss++;
flush_page_to_ram(page);
@@ -1260,10 +1267,10 @@
/* No need to invalidate - it was non-present before */
update_mmu_cache(vma, addr, entry);
spin_unlock(&mm->page_table_lock);
- return 1; /* Minor fault */
+ return VM_FAULT_MINOR;
no_mem:
- return -1;
+ return VM_FAULT_OOM;
}
/*
@@ -1291,10 +1298,11 @@
new_page = vma->vm_ops->nopage(vma, address & PAGE_MASK, 0);
- if (new_page == NULL) /* no page was available -- SIGBUS */
- return 0;
+ /* no page was available -- either SIGBUS or OOM */
+ if (new_page == NOPAGE_SIGBUS)
+ return VM_FAULT_SIGBUS;
if (new_page == NOPAGE_OOM)
- return -1;
+ return VM_FAULT_OOM;
/*
* Should we do an early C-O-W break?
@@ -1303,7 +1311,7 @@
struct page * page = alloc_page(GFP_HIGHUSER);
if (!page) {
page_cache_release(new_page);
- return -1;
+ return VM_FAULT_OOM;
}
copy_user_highpage(page, new_page, address);
page_cache_release(new_page);
@@ -1339,13 +1347,13 @@
pte_unmap(page_table);
page_cache_release(new_page);
spin_unlock(&mm->page_table_lock);
- return 1;
+ return VM_FAULT_MINOR;
}
/* no need to invalidate: a not-present page shouldn't be cached */
update_mmu_cache(vma, address, entry);
spin_unlock(&mm->page_table_lock);
- return 2; /* Major fault */
+ return VM_FAULT_MAJOR;
}
/*
@@ -1397,7 +1405,7 @@
establish_pte(vma, address, pte, entry);
pte_unmap(pte);
spin_unlock(&mm->page_table_lock);
- return 1;
+ return VM_FAULT_MINOR;
}
/*
@@ -1425,7 +1433,7 @@
return handle_pte_fault(mm, vma, address, write_access, pte, pmd);
}
spin_unlock(&mm->page_table_lock);
- return -1;
+ return VM_FAULT_OOM;
}
/*
===== arch/i386/mm/fault.c 1.13 vs edited =====
--- 1.13/arch/i386/mm/fault.c Tue Feb 26 17:13:20 2002
+++ edited/arch/i386/mm/fault.c Fri Jun 7 15:26:47 2002
@@ -56,12 +56,16 @@
for (;;) {
survive:
- {
- int fault = handle_mm_fault(current->mm, vma, start, 1);
- if (!fault)
+ switch (handle_mm_fault(current->mm, vma, start, 1)) {
+ case VM_FAULT_SIGBUS:
goto bad_area;
- if (fault < 0)
+ case VM_FAULT_OOM:
goto out_of_memory;
+ case VM_FAULT_MINOR:
+ case VM_FAULT_MAJOR:
+ break;
+ default:
+ BUG();
}
if (!size)
break;
@@ -239,16 +243,18 @@
* the fault.
*/
switch (handle_mm_fault(mm, vma, address, write)) {
- case 1:
- tsk->min_flt++;
- break;
- case 2:
- tsk->maj_flt++;
- break;
- case 0:
- goto do_sigbus;
- default:
- goto out_of_memory;
+ case VM_FAULT_MINOR:
+ tsk->min_flt++;
+ break;
+ case VM_FAULT_MAJOR:
+ tsk->maj_flt++;
+ break;
+ case VM_FAULT_SIGBUS:
+ goto do_sigbus;
+ case VM_FAULT_OOM:
+ goto out_of_memory;
+ default:
+ BUG();
}
/*
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
This archive was generated by hypermail 2b29 : Fri Jun 07 2002 - 22:00:31 EST