[PATCH 03 of 13] prevent oom deadlocks during read/write operations

[Andrea Arcangeli <andrea@cpushare.com>]

# HG changeset patch
# User Andrea Arcangeli <andrea@suse.de>
# Date 1199469588 -3600
# Node ID 4091a7ef36c80c3d2fa0d60a7b8bd885da68154d
# Parent  ddd02ad798f6902fc561843c60f1189a44fdb439
prevent oom deadlocks during read/write operations

We need to react to SIGKILL during read/write with huge buffers or it
becomes too easy to prevent a SIGKILLED task to run do_exit promptly
after it has been selected for oom-killage.

Signed-off-by: Andrea Arcangeli <andrea@suse.de>

diff --git a/mm/filemap.c b/mm/filemap.c
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -927,6 +927,16 @@ page_ok:
 		isize = i_size_read(inode);
 		end_index = (isize - 1) >> PAGE_CACHE_SHIFT;
 		if (unlikely(!isize || index > end_index)) {
+			page_cache_release(page);
+			goto out;
+		}
+
+		if (unlikely(sigismember(&current->pending.signal, SIGKILL))) {
+			/*
+			 * Must not hang almost forever in D state in
+			 * presence of sigkill and lots of ram/swap
+			 * (think during OOM).
+			 */
 			page_cache_release(page);
 			goto out;
 		}
@@ -2063,6 +2073,16 @@ static ssize_t generic_perform_write_2co
 			break;
 		}
 
+		if (unlikely(sigismember(&current->pending.signal, SIGKILL))) {
+			/*
+			 * Must not hang almost forever in D state in
+			 * presence of sigkill and lots of ram/swap
+			 * (think during OOM).
+			 */
+			status = -ENOMEM;
+			break;
+		}
+
 		page = __grab_cache_page(mapping, index);
 		if (!page) {
 			status = -ENOMEM;
@@ -2230,6 +2250,16 @@ again:
 		 */
 		if (unlikely(iov_iter_fault_in_readable(i, bytes))) {
 			status = -EFAULT;
+			break;
+		}
+
+		if (unlikely(sigismember(&current->pending.signal, SIGKILL))) {
+			status = -ENOMEM;
+			/*
+			 * Must not hang almost forever in D state in
+			 * presence of sigkill and lots of ram/swap
+			 * (think during OOM).
+			 */
 			break;
 		}
 

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