linux-kernel - Re: [PATCH] fix readahead pipeline break caused by block plug

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Tue, 31 Jan 2012 18:34:16 +0800
From:	Wu Fengguang <wfg@...ux.intel.com>
To:	Shaohua Li <shaohua.li@...el.com>
Cc:	lkml <linux-kernel@...r.kernel.org>, linux-mm <linux-mm@...ck.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Jens Axboe <axboe@...nel.dk>,
	Herbert Poetzl <herbert@...hfloor.at>,
	Eric Dumazet <eric.dumazet@...il.com>,
	Vivek Goyal <vgoyal@...hat.com>
Subject: Re: [PATCH] fix readahead pipeline break caused by block plug

I'd like to propose a sister patch on the write part. It may not be
as easy to measure any performance impacts of it, but I'll try.

---
Subject: remove plugging at buffered write time 
Date: Tue Jan 31 18:25:48 CST 2012

Buffered write(2) is not directly tied to IO, so no need to handle plug
in generic_file_aio_write().

CC: Jens Axboe <axboe@...nel.dk>
CC: Li Shaohua <shaohua.li@...el.com>
Signed-off-by: Wu Fengguang <fengguang.wu@...el.com>
---
 mm/filemap.c |    6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

--- linux-next.orig/mm/filemap.c	2012-01-31 18:23:52.000000000 +0800
+++ linux-next/mm/filemap.c	2012-01-31 18:25:38.000000000 +0800
@@ -2267,6 +2267,7 @@ generic_file_direct_write(struct kiocb *
 	struct file	*file = iocb->ki_filp;
 	struct address_space *mapping = file->f_mapping;
 	struct inode	*inode = mapping->host;
+	struct blk_plug plug;
 	ssize_t		written;
 	size_t		write_len;
 	pgoff_t		end;
@@ -2301,7 +2302,9 @@ generic_file_direct_write(struct kiocb *
 		}
 	}
 
+	blk_start_plug(&plug);
 	written = mapping->a_ops->direct_IO(WRITE, iocb, iov, pos, *nr_segs);
+	blk_finish_plug(&plug);
 
 	/*
 	 * Finally, try again to invalidate clean pages which might have been
@@ -2610,13 +2613,11 @@ ssize_t generic_file_aio_write(struct ki
 {
 	struct file *file = iocb->ki_filp;
 	struct inode *inode = file->f_mapping->host;
-	struct blk_plug plug;
 	ssize_t ret;
 
 	BUG_ON(iocb->ki_pos != pos);
 
 	mutex_lock(&inode->i_mutex);
-	blk_start_plug(&plug);
 	ret = __generic_file_aio_write(iocb, iov, nr_segs, &iocb->ki_pos);
 	mutex_unlock(&inode->i_mutex);
 
@@ -2627,7 +2628,6 @@ ssize_t generic_file_aio_write(struct ki
 		if (err < 0 && ret > 0)
 			ret = err;
 	}
-	blk_finish_plug(&plug);
 	return ret;
 }
 EXPORT_SYMBOL(generic_file_aio_write);
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/