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authorYing Han <yinghan@google.com>2009-01-06 17:40:18 -0500
committerLinus Torvalds <torvalds@linux-foundation.org>2009-01-06 18:59:08 -0500
commit4779280d1ea4d361af13ae77ba55217fbcd16d4c (patch)
tree1abb35d85f2280aebb9cd565cc223d14b8731203 /mm/memory.c
parent91bf189c3a766927694ce9de7d545e96b23f20fc (diff)
mm: make get_user_pages() interruptible
The initial implementation of checking TIF_MEMDIE covers the cases of OOM killing. If the process has been OOM killed, the TIF_MEMDIE is set and it return immediately. This patch includes: 1. add the case that the SIGKILL is sent by user processes. The process can try to get_user_pages() unlimited memory even if a user process has sent a SIGKILL to it(maybe a monitor find the process exceed its memory limit and try to kill it). In the old implementation, the SIGKILL won't be handled until the get_user_pages() returns. 2. change the return value to be ERESTARTSYS. It makes no sense to return ENOMEM if the get_user_pages returned by getting a SIGKILL signal. Considering the general convention for a system call interrupted by a signal is ERESTARTNOSYS, so the current return value is consistant to that. Lee: An unfortunate side effect of "make-get_user_pages-interruptible" is that it prevents a SIGKILL'd task from munlock-ing pages that it had mlocked, resulting in freeing of mlocked pages. Freeing of mlocked pages, in itself, is not so bad. We just count them now--altho' I had hoped to remove this stat and add PG_MLOCKED to the free pages flags check. However, consider pages in shared libraries mapped by more than one task that a task mlocked--e.g., via mlockall(). If the task that mlocked the pages exits via SIGKILL, these pages would be left mlocked and unevictable. Proposed fix: Add another GUP flag to ignore sigkill when calling get_user_pages from munlock()--similar to Kosaki Motohiro's 'IGNORE_VMA_PERMISSIONS flag for the same purpose. We are not actually allocating memory in this case, which "make-get_user_pages-interruptible" intends to avoid. We're just munlocking pages that are already resident and mapped, and we're reusing get_user_pages() to access those pages. ?? Maybe we should combine 'IGNORE_VMA_PERMISSIONS and '_IGNORE_SIGKILL into a single flag: GUP_FLAGS_MUNLOCK ??? [Lee.Schermerhorn@hp.com: ignore sigkill in get_user_pages during munlock] Signed-off-by: Paul Menage <menage@google.com> Signed-off-by: Ying Han <yinghan@google.com> Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Reviewed-by: Pekka Enberg <penberg@cs.helsinki.fi> Cc: Nick Piggin <nickpiggin@yahoo.com.au> Cc: Hugh Dickins <hugh@veritas.com> Cc: Oleg Nesterov <oleg@tv-sign.ru> Cc: Lee Schermerhorn <lee.schermerhorn@hp.com> Cc: Rohit Seth <rohitseth@google.com> Cc: David Rientjes <rientjes@google.com> Signed-off-by: Lee Schermerhorn <lee.schermerhorn@hp.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/memory.c')
-rw-r--r--mm/memory.c14
1 files changed, 9 insertions, 5 deletions
diff --git a/mm/memory.c b/mm/memory.c
index db68af8e0bc4..3f8fa06b963b 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1210,6 +1210,7 @@ int __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
1210 int write = !!(flags & GUP_FLAGS_WRITE); 1210 int write = !!(flags & GUP_FLAGS_WRITE);
1211 int force = !!(flags & GUP_FLAGS_FORCE); 1211 int force = !!(flags & GUP_FLAGS_FORCE);
1212 int ignore = !!(flags & GUP_FLAGS_IGNORE_VMA_PERMISSIONS); 1212 int ignore = !!(flags & GUP_FLAGS_IGNORE_VMA_PERMISSIONS);
1213 int ignore_sigkill = !!(flags & GUP_FLAGS_IGNORE_SIGKILL);
1213 1214
1214 if (len <= 0) 1215 if (len <= 0)
1215 return 0; 1216 return 0;
@@ -1288,12 +1289,15 @@ int __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
1288 struct page *page; 1289 struct page *page;
1289 1290
1290 /* 1291 /*
1291 * If tsk is ooming, cut off its access to large memory 1292 * If we have a pending SIGKILL, don't keep faulting
1292 * allocations. It has a pending SIGKILL, but it can't 1293 * pages and potentially allocating memory, unless
1293 * be processed until returning to user space. 1294 * current is handling munlock--e.g., on exit. In
1295 * that case, we are not allocating memory. Rather,
1296 * we're only unlocking already resident/mapped pages.
1294 */ 1297 */
1295 if (unlikely(test_tsk_thread_flag(tsk, TIF_MEMDIE))) 1298 if (unlikely(!ignore_sigkill &&
1296 return i ? i : -ENOMEM; 1299 fatal_signal_pending(current)))
1300 return i ? i : -ERESTARTSYS;
1297 1301
1298 if (write) 1302 if (write)
1299 foll_flags |= FOLL_WRITE; 1303 foll_flags |= FOLL_WRITE;