[PATCH] Free the temporary vfsmount created in bdev_cache_init()

[PATCH] Free the temporary vfsmount created in bdev_cache_init()

[Catalin Marinas]

The vfsmount structure allocated in this function (the bd_mnt local
variable) is only used to obtain the blockdev_superblock and there are
no other references to it. This structure can be safely freed (and
prevent kmemleak from reporting it).

Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Cheng Renquan <crquan@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
---

This patch was submitted and acked some time ago but I don't think it
made it into the kernel. Here it is again. Thanks.

 fs/block_dev.c |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)

diff --git a/fs/block_dev.c b/fs/block_dev.c
index 8c3c689..e7a332f 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -492,6 +492,7 @@ void __init bdev_cache_init(void)
 	if (IS_ERR(bd_mnt))
 		panic("Cannot create bdev pseudo-fs");
 	blockdev_superblock = bd_mnt->mnt_sb;	/* For writeback */
+	free_vfsmnt(bd_mnt);
 }
 
 /*

Re: [PATCH] Free the temporary vfsmount created in bdev_cache_init()

[Al Viro]

On Wed, Apr 01, 2009 at 12:07:37PM +0100, Catalin Marinas wrote:
> The vfsmount structure allocated in this function (the bd_mnt local
> variable) is only used to obtain the blockdev_superblock and there are
> no other references to it. This structure can be safely freed (and
> prevent kmemleak from reporting it).

NAK.  This kind of kludges is simply not worth doing.  Store the
pointer to vfsmount into a static-in-file variable if you want
to get kmemleak to STFU.

Savings on a vfsmount are not worth neurons needed to remember that
in this particular case we are OK to do something that is utterly
wrong in general (free_vfsmnt() is a very low-level stuff that shouldn't
be used outside of namespace.c and super.c).

Re: [PATCH] Free the temporary vfsmount created in bdev_cache_init()

[Catalin Marinas]

On Wed, 2009-04-01 at 12:49 +0100, Al Viro wrote:
> On Wed, Apr 01, 2009 at 12:07:37PM +0100, Catalin Marinas wrote:
> > The vfsmount structure allocated in this function (the bd_mnt local
> > variable) is only used to obtain the blockdev_superblock and there are
> > no other references to it. This structure can be safely freed (and
> > prevent kmemleak from reporting it).
> 
> NAK.  This kind of kludges is simply not worth doing.  Store the
> pointer to vfsmount into a static-in-file variable if you want
> to get kmemleak to STFU.

That's how it used to be until commit c2acf7b9 made bd_mnt a local
variable. Rather than reverting part of this commit, I can add a
kmemleak_ignore() call to shut it up.

-- 
Catalin

[PATCH] Free the temporary vfsmount created in bdev_cache_init()

[Catalin Marinas]

The vfsmount structure allocated in this function (the bd_mnt local
variable) is only used to obtain the blockdev_superblock and there are
no other references to it. This structure can be safely freed.

Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Cheng Renquan <crquan@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
---
 fs/block_dev.c |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)

diff --git a/fs/block_dev.c b/fs/block_dev.c
index b3c1eff..5124756 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -346,6 +346,7 @@ void __init bdev_cache_init(void)
 	if (IS_ERR(bd_mnt))
 		panic("Cannot create bdev pseudo-fs");
 	blockdev_superblock = bd_mnt->mnt_sb;	/* For writeback */
+	free_vfsmnt(bd_mnt);
 }
 
 /*