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Subject[PATCH 3/3] 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>

--- 26-rc2/mm/filemap.c~3_INIT_READ 2008-05-18 15:44:19.000000000 +0400
+++ 26-rc2/mm/filemap.c 2008-06-08 19:23:51.000000000 +0400
@@ -1000,8 +1000,9 @@ 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;

/* Did it get truncated before we got the lock? */
if (!page->mapping) {
@@ -1029,8 +1030,9 @@ 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) {
/*
@@ -1042,15 +1044,14 @@ 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;


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