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 876bc59..494ff20 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -1100,8 +1100,9 @@
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 @@
}
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 @@
}
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;