From: Oleg Nesterov <oleg@tv-sign.ru>
Date: Sun, 8 Jun 2008 17:20:43 +0000 (+0400)
Subject: do_generic_file_read: s/EINTR/EIO/ if lock_page_killable() fails
X-Git-Tag: v2.6.28-rc1~271^2^6
X-Git-Url: http://www.pilppa.org/gitweb/gitweb.cgi?a=commitdiff_plain;h=85462323555dda749f1c5373a8d72679464c968d;p=linux-2.6-omap-h63xx.git

do_generic_file_read: s/EINTR/EIO/ if lock_page_killable() fails

If lock_page_killable() fails because the task was killed by SIGKILL or
any other fatal signal, do_generic_file_read() returns -EIO.

This seems to be OK, because in fact the userspace won't see this error,
the task will dequeue SIGKILL and exit.

However, /sbin/init is different, it will dequeue SIGKILL, ignore it, and
return to the user-space with the bogus -EIO.

Change the code to return the error code from lock_page_killable(), -EINTR.
This doesn't fix the bug, but perhaps makes sense anyway. Imho, with this
change the code looks a bit more logical, and the "good" init should handle
the spurious EINTR or short read.

Afaics we can also change lock_page_killable() to return -ERESTARTNOINTR,
but this can't prevent the short reads.

Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
---

diff --git a/mm/filemap.c b/mm/filemap.c
index 876bc595d0f..494ff20b6cf 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -1100,8 +1100,9 @@ page_ok:
 
 page_not_up_to_date:
 		/* Get exclusive access to the page ... */
-		if (lock_page_killable(page))
-			goto readpage_eio;
+		error = lock_page_killable(page);
+		if (unlikely(error))
+			goto readpage_error;
 
 page_not_up_to_date_locked:
 		/* Did it get truncated before we got the lock? */
@@ -1130,8 +1131,9 @@ readpage:
 		}
 
 		if (!PageUptodate(page)) {
-			if (lock_page_killable(page))
-				goto readpage_eio;
+			error = lock_page_killable(page);
+			if (unlikely(error))
+				goto readpage_error;
 			if (!PageUptodate(page)) {
 				if (page->mapping == NULL) {
 					/*
@@ -1143,15 +1145,14 @@ readpage:
 				}
 				unlock_page(page);
 				shrink_readahead_size_eio(filp, ra);
-				goto readpage_eio;
+				error = -EIO;
+				goto readpage_error;
 			}
 			unlock_page(page);
 		}
 
 		goto page_ok;
 
-readpage_eio:
-		error = -EIO;
 readpage_error:
 		/* UHHUH! A synchronous read error occurred. Report it */
 		desc->error = error;