From: Jeff Moyer <jmoyer@redhat.com>
To: linux-kernel@vger.kernel.org
Cc: mingo@redhat.com, sct@redhat.com
Subject: [patch rfc] towards supporting O_NONBLOCK on regular files
Date: Fri, 1 Oct 2004 16:57:50 -0400 [thread overview]
Message-ID: <16733.50382.569265.183099@segfault.boston.redhat.com> (raw)
This patch makes an attempt at supporting the O_NONBLOCK flag for regular
files. It's pretty straight-forward. One limitation is that we still call
into the readahead code, which I believe can block. However, if we don't
do this, then an application which only uses non-blocking reads may never
get it's data.
Comments welcome.
-Jeff
--- linux-2.6.8/mm/filemap.c.orig 2004-09-30 16:33:46.881129560 -0400
+++ linux-2.6.8/mm/filemap.c 2004-09-30 16:34:12.109294296 -0400
@@ -720,7 +720,7 @@ void do_generic_mapping_read(struct addr
unsigned long index, end_index, offset;
loff_t isize;
struct page *cached_page;
- int error;
+ int error, nonblock = filp->f_flags & O_NONBLOCK;
struct file_ra_state ra = *_ra;
cached_page = NULL;
@@ -755,10 +755,20 @@ find_page:
page = find_get_page(mapping, index);
if (unlikely(page == NULL)) {
handle_ra_miss(mapping, &ra, index);
+ if (nonblock) {
+ desc->error = -EWOULDBLOCK;
+ break;
+ }
goto no_cached_page;
}
- if (!PageUptodate(page))
+ if (!PageUptodate(page)) {
+ if (nonblock) {
+ page_cache_release(page);
+ desc->error = -EWOULDBLOCK;
+ break;
+ }
goto page_not_up_to_date;
+ }
page_ok:
/* If users can be writing to this page using arbitrary
@@ -1004,7 +1014,7 @@ __generic_file_aio_read(struct kiocb *io
desc.error = 0;
do_generic_file_read(filp,ppos,&desc,file_read_actor);
retval += desc.written;
- if (!retval) {
+ if (!retval || desc.error) {
retval = desc.error;
break;
}
next reply other threads:[~2004-10-01 21:17 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-10-01 20:57 Jeff Moyer [this message]
2004-10-03 19:48 ` [patch rfc] towards supporting O_NONBLOCK on regular files Pavel Machek
2004-10-13 14:28 ` Jeff Moyer
2004-10-14 17:39 ` Pavel Machek
2004-10-05 11:27 ` Marcelo Tosatti
2004-10-06 13:13 ` Jeff Moyer
2004-10-06 12:01 ` Marcelo Tosatti
2004-10-07 3:31 ` Stephen C. Tweedie
2004-10-07 10:12 ` Marcelo Tosatti
2004-10-07 12:30 ` Arjan van de Ven
2004-10-11 18:32 ` Stephen C. Tweedie
2004-10-11 18:58 ` Jeff Moyer
2004-10-11 21:49 ` Stephen C. Tweedie
2004-10-13 14:26 ` Jeff Moyer
2004-10-15 15:44 ` Jeff Moyer
2004-10-15 16:19 ` Stephen C. Tweedie
2004-10-17 7:59 ` Alexandre Oliva
2004-10-17 11:20 ` Ingo Molnar
2004-10-17 19:38 ` Alexandre Oliva
2004-10-18 16:51 ` Jeff Moyer
2004-10-19 6:04 ` Alexandre Oliva
2004-10-21 20:14 ` James Antill
2004-10-05 15:35 ` Rik van Riel
2004-10-05 13:07 Dan Kegel
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=16733.50382.569265.183099@segfault.boston.redhat.com \
--to=jmoyer@redhat.com \
--cc=linux-kernel@vger.kernel.org \
--cc=mingo@redhat.com \
--cc=sct@redhat.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).