linux-kernel - Re: [PATCH 0/7] rwsem: Implement down_read

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Message-ID: <20170620103648.vi7v45mjk63msw72@virtuozzo.com>
Date:   Tue, 20 Jun 2017 13:36:50 +0300
From:   Kirill Tkhai <ktkhai@...tuozzo.com>
To:     David Howells <dhowells@...hat.com>,
        Al Viro <viro@...iv.linux.org.uk>
Cc:     David Rientjes <rientjes@...gle.com>, linux-ia64@...r.kernel.org,
        avagin@...tuozzo.com, peterz@...radead.org,
        heiko.carstens@...ibm.com, hpa@...or.com, gorcunov@...tuozzo.com,
        linux-arch@...r.kernel.org, linux-s390@...r.kernel.org,
        x86@...nel.org, mingo@...hat.com, mattst88@...il.com,
        fenghua.yu@...el.com, arnd@...db.de, ink@...assic.park.msu.ru,
        tglx@...utronix.de, rth@...ddle.net, tony.luck@...el.com,
        linux-kernel@...r.kernel.org, linux-alpha@...r.kernel.org,
        schwidefsky@...ibm.com, davem@...emloft.net
Subject: Re: [PATCH 0/7] rwsem: Implement down_read_killable()

On Tue, Jun 20, 2017 at 09:30, David Howells wrote:
> David Rientjes <rientjes@...gle.com> wrote:
> 
> > I would have expected to see down_read_killable() actually used somewhere 
> > after its implementation as part of this patchset.
> 
> There are some places we should be using down_{read|write}_interruptible(), if
> it existed, dressed as inode_lock{,_shared}_interruptible().

Then let's use it in iterate_dir():

[PATCH]fs: Use killable down_read() in iterate_dir()

There was mutex_lock_interruptible() initially, and it was changed
to rwsem, but there were not killable rwsem primitives that time.
>From commit 9902af79c01a:
    
    "The main issue is the lack of down_write_killable(), so the places
     like readdir.c switched to plain inode_lock(); once killable
     variants of rwsem primitives appear, that'll be dealt with"

Use down_read_killable() same as down_write_killable() in !shared
case, as concurrent inode_lock() may take much time, that may be
wanted to be interrupted by user.

Signed-off-by: Kirill Tkhai <ktkhai@...tuozzo.com>
---
 fs/readdir.c | 11 +++++------
 1 file changed, 5 insertions(+), 6 deletions(-)

diff --git a/fs/readdir.c b/fs/readdir.c
index 89659549c09d..7c584bbb4ce3 100644
--- a/fs/readdir.c
+++ b/fs/readdir.c
@@ -36,13 +36,12 @@ int iterate_dir(struct file *file, struct dir_context *ctx)
 	if (res)
 		goto out;
 
-	if (shared) {
-		inode_lock_shared(inode);
-	} else {
+	if (shared)
+		res = down_read_killable(&inode->i_rwsem);
+	else
 		res = down_write_killable(&inode->i_rwsem);
-		if (res)
-			goto out;
-	}
+	if (res)
+		goto out;
 
 	res = -ENOENT;
 	if (!IS_DEADDIR(inode)) {