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From: "J. Bruce Fields" <bfields@fieldses.org>
To: Amir Goldstein <amir73il@gmail.com>
Cc: Jeff Layton <jlayton@kernel.org>,
	Volker.Lendecke@sernet.de, samba-technical@lists.samba.org,
	Linux NFS Mailing List <linux-nfs@vger.kernel.org>,
	linux-fsdevel <linux-fsdevel@vger.kernel.org>,
	Pavel Shilovsky <piastryyy@gmail.com>
Subject: Re: Better interop for NFS/SMB file share mode/reservation
Date: Thu, 14 Feb 2019 15:51:00 -0500	[thread overview]
Message-ID: <20190214205100.GB9216@fieldses.org> (raw)
In-Reply-To: <CAOQ4uxjV2FahWEtESJJRwz0kkBZxkKosCnURzj2HtuKNwhscng@mail.gmail.com>

On Fri, Feb 08, 2019 at 10:31:07PM +0200, Amir Goldstein wrote:
> On Fri, Feb 8, 2019 at 10:17 PM J. Bruce Fields <bfields@fieldses.org> wrote:
> > On Fri, Feb 08, 2019 at 10:02:43PM +0200, Amir Goldstein wrote:
> > > On Fri, Feb 8, 2019 at 5:51 PM J. Bruce Fields <bfields@fieldses.org> wrote:
> > > > On Fri, Feb 08, 2019 at 04:45:46PM +0200, Amir Goldstein wrote:
> > > > > - check_conflicting_open() is changed to use inode_is_open_for_read()
> > > > >   instead of checking d_count and i_count.
> > > >
> > > > Independently of the rest, I'd love to do away with those
> > > > d_count/i_count checks.  What's inode_is_open_for_read()?
> > > >
> > >
> > > It would look maybe something like this:
> > >
> > > static inline bool file_is_open_for_read(const struct inode *file)
> > > {
> > >         struct inode *inode = file_inode(file);
> > >         int countself = (file->f_mode & (FMODE_READ | FMODE_WRITE)) ==
> > > FMODE_READ) ? 1 : 0;
> > >
> > >         return atomic_read(&inode->i_readcount) > countself;
> > > }
> > >
> > > And it would allow for acquiring F_WRLCK lease if other
> > > instances of inode are open O_PATH.
> > > A slight change of semantics that seems harmless(?)
> > > and will allow some flexibility.
> >
> > How did I not know about i_readcount?  (Looking)  I guess it would mean
> > adding some dependence on CONFIG_IMA, hm.
> >
> 
> Yes, or we remove ifdef CONFIG_IMA from i_readcount.
> I am not sure if the concern was size of struct inode
> (shouldn't increase on 64bit arch) or the accounting on
> open/close. The impact doesn't look significant (?)..

Looks like the original patch was d984ea604943bb "fs: move i_readcount".
I did some googling around and looked at the discussion summarized by
https://lwn.net/Articles/410895/ but can't find useful discussion of
i_readcount impact.

Looks like CONFIG_IMA is on in Fedora and RHEL, for what it's worth.

Maybe something like this?

--b.

commit 02cfda99ed8c
Author: J. Bruce Fields <bfields@redhat.com>
Date:   Thu Feb 14 15:02:02 2019 -0500

    locks: use i_readcount to detect lease conflicts
    
    The lease code currently uses the inode and dentry refcounts to detect
    whether someone has a file open for read.  This seems fragile.  Use
    i_readcount instead.
    
    Signed-off-by: J. Bruce Fields <bfields@redhat.com>

diff --git a/fs/locks.c b/fs/locks.c
index ff6af2c32601..299abad65545 100644
--- a/fs/locks.c
+++ b/fs/locks.c
@@ -1769,8 +1769,7 @@ check_conflicting_open(const struct dentry *dentry, const long arg, int flags)
 	if ((arg == F_RDLCK) && inode_is_open_for_write(inode))
 		return -EAGAIN;
 
-	if ((arg == F_WRLCK) && ((d_count(dentry) > 1) ||
-	    (atomic_read(&inode->i_count) > 1)))
+	if ((arg == F_WRLCK) && (atomic_read(&inode->i_readcount) > 1))
 		ret = -EAGAIN;
 
 	return ret;
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 29d8e2cfed0e..e862de682da9 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -676,7 +676,7 @@ struct inode {
 	atomic_t		i_count;
 	atomic_t		i_dio_count;
 	atomic_t		i_writecount;
-#ifdef CONFIG_IMA
+#if defined(CONFIG_IMA) || (defined_CONFIG_FILE_LOCKING)
 	atomic_t		i_readcount; /* struct files open RO */
 #endif
 	const struct file_operations	*i_fop;	/* former ->i_op->default_file_ops */
@@ -2869,7 +2869,7 @@ static inline bool inode_is_open_for_write(const struct inode *inode)
 	return atomic_read(&inode->i_writecount) > 0;
 }
 
-#ifdef CONFIG_IMA
+#if defined(CONFIG_IMA) || defined(CONFIG_FILE_LOCKING)
 static inline void i_readcount_dec(struct inode *inode)
 {
 	BUG_ON(!atomic_read(&inode->i_readcount));

  reply	other threads:[~2019-02-14 20:51 UTC|newest]

Thread overview: 45+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-02-08 11:20 Better interop for NFS/SMB file share mode/reservation Amir Goldstein
2019-02-08 13:10 ` Jeff Layton
2019-02-08 14:45   ` Amir Goldstein
2019-02-08 15:50     ` J. Bruce Fields
2019-02-08 20:02       ` Amir Goldstein
2019-02-08 20:16         ` J. Bruce Fields
2019-02-08 20:31           ` Amir Goldstein
2019-02-14 20:51             ` J. Bruce Fields [this message]
2019-02-15  7:31               ` Amir Goldstein
2019-02-15 20:09                 ` J. Bruce Fields
2019-02-08 22:12         ` Jeremy Allison
2019-02-09  4:04           ` Amir Goldstein
2019-02-14 21:06             ` J. Bruce Fields
2019-03-05 21:47               ` J. Bruce Fields
2019-03-06  7:09                 ` Amir Goldstein
2019-03-06 15:17                   ` J. Bruce Fields
2019-03-06 15:37                     ` [NFS-Ganesha-Devel] " Frank Filz
2019-03-08 21:38                       ` 'J. Bruce Fields'
2019-03-08 21:53                         ` Frank Filz
2019-03-06 15:11                 ` J. Bruce Fields
2019-03-06 20:31                   ` Jeff Layton
2019-03-06 21:07                     ` Jeremy Allison
2019-03-06 21:25                       ` Ralph Böhme
2019-03-07 11:03                         ` Stefan Metzmacher
2019-03-07 16:47                           ` Simo
2019-04-25 18:11                           ` Amir Goldstein
2019-03-06 21:55                       ` Jeff Layton
2019-02-08 16:03     ` Jeff Layton
2019-02-08 16:28       ` Jeffrey Layton
     [not found]       ` <CAOQ4uxgQsRaEOxz1aYzP1_1fzRpQbOm2-wuzG=ABAphPB=7Mxg@mail.gmail.com>
     [not found]         ` <20190426140023.GB25827@fieldses.org>
     [not found]           ` <CAOQ4uxhuxoEsoBbvenJ8eLGstPc4AH-msrxDC-tBFRhvDxRSNg@mail.gmail.com>
     [not found]             ` <20190426145006.GD25827@fieldses.org>
     [not found]               ` <e69d149c80187b84833fec369ad8a51247871f26.camel@kernel.org>
2019-04-27 20:16                 ` Amir Goldstein
2019-04-28 12:09                   ` Jeff Layton
2019-04-28 13:45                     ` Amir Goldstein
2019-04-28 15:06                       ` Trond Myklebust
2019-04-28 22:00                         ` Amir Goldstein
2019-04-28 22:08                           ` Trond Myklebust
2019-04-28 22:33                             ` Amir Goldstein
2019-04-29  0:57                               ` Trond Myklebust
2019-04-29 11:42                                 ` Amir Goldstein
2019-04-29 13:10                                   ` Trond Myklebust
2019-04-29 20:29                                 ` Jeff Layton
2019-04-29 22:33                                   ` Pavel Shilovskiy
2019-04-30  0:31                                     ` Amir Goldstein
2019-04-30  8:12                                       ` Uri Simchoni
2019-04-30  9:22                                         ` Amir Goldstein
2019-02-11  5:31     ` ronnie sahlberg

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