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Commit 85462323 authored by Oleg Nesterov's avatar Oleg Nesterov Committed by Ingo Molnar
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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: default avatarOleg Nesterov <oleg@tv-sign.ru>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 7591103c

mm/filemap.c

+8 −7
Original line number Diff line number Diff line
@@ -1100,8 +1100,9 @@ static void do_generic_file_read(struct file *filp, loff_t *ppos, 


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 @@ static void do_generic_file_read(struct file *filp, loff_t *ppos, 
		}



		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 @@ static void do_generic_file_read(struct file *filp, loff_t *ppos, 
				}

				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;