* Minor kmemleak report via bdev_cache_init
@ 2009-01-06 18:25 Catalin Marinas
2009-01-12 23:54 ` Andrew Morton
0 siblings, 1 reply; 3+ messages in thread
From: Catalin Marinas @ 2009-01-06 18:25 UTC (permalink / raw)
To: Denis ChengRq; +Cc: Andrew Morton, linux-kernel
Hi Denis,
With the commit c2acf7b908217 (fs/block_dev.c: __read_mostly improvement
and sb_is_blkdev_sb utilization), the bd_mnt is only local and kmemleak
reports the corresponding vfsmnt structure as unreferenced (together
with the duplicated name) since it can no longer track a valid pointer
to it:
unreferenced object 0xdf813848 (size 128):
comm "swapper", pid 0, jiffies 4294937384
backtrace:
[<c00872c0>] kmemleak_alloc+0x144/0x27c
[<c00848c8>] kmem_cache_alloc+0x108/0x13c
[<c009fc00>] alloc_vfsmnt+0x20/0x144
[<c008bc34>] vfs_kern_mount+0x30/0xac
[<c008bccc>] kern_mount_data+0x1c/0x20
[<c00104a8>] bdev_cache_init+0x54/0x90
[<c000fd7c>] vfs_caches_init+0xfc/0x128
[<c0008984>] start_kernel+0x1f8/0x254
unreferenced object 0xdf8033d0 (size 32):
comm "swapper", pid 0, jiffies 4294937384
backtrace:
[<c00872c0>] kmemleak_alloc+0x144/0x27c
[<c0085e10>] __kmalloc_track_caller+0x15c/0x194
[<c0071704>] kstrdup+0x3c/0x58
[<c009fc5c>] alloc_vfsmnt+0x7c/0x144
[<c008bc34>] vfs_kern_mount+0x30/0xac
[<c008bccc>] kern_mount_data+0x1c/0x20
[<c00104a8>] bdev_cache_init+0x54/0x90
[<c000fd7c>] vfs_caches_init+0xfc/0x128
[<c0008984>] start_kernel+0x1f8/0x254
Can this object be freed (as below) or should I just tell kmemleak to
ignore it (or is it referenced and that's a kmemleak false positive)?
diff --git a/fs/block_dev.c b/fs/block_dev.c
index 349a26c..78e469c 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -344,6 +344,7 @@ 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);
}
/*
Thanks.
--
Catalin
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: Minor kmemleak report via bdev_cache_init
2009-01-06 18:25 Minor kmemleak report via bdev_cache_init Catalin Marinas
@ 2009-01-12 23:54 ` Andrew Morton
2009-01-13 6:19 ` Cheng Renquan
0 siblings, 1 reply; 3+ messages in thread
From: Andrew Morton @ 2009-01-12 23:54 UTC (permalink / raw)
To: Catalin Marinas; +Cc: crquan, linux-kernel, Al Viro
On Tue, 06 Jan 2009 18:25:34 +0000
Catalin Marinas <catalin.marinas@arm.com> wrote:
> Hi Denis,
>
> With the commit c2acf7b908217 (fs/block_dev.c: __read_mostly improvement
> and sb_is_blkdev_sb utilization), the bd_mnt is only local and kmemleak
> reports the corresponding vfsmnt structure as unreferenced (together
> with the duplicated name) since it can no longer track a valid pointer
> to it:
>
> unreferenced object 0xdf813848 (size 128):
> comm "swapper", pid 0, jiffies 4294937384
> backtrace:
> [<c00872c0>] kmemleak_alloc+0x144/0x27c
> [<c00848c8>] kmem_cache_alloc+0x108/0x13c
> [<c009fc00>] alloc_vfsmnt+0x20/0x144
> [<c008bc34>] vfs_kern_mount+0x30/0xac
> [<c008bccc>] kern_mount_data+0x1c/0x20
> [<c00104a8>] bdev_cache_init+0x54/0x90
> [<c000fd7c>] vfs_caches_init+0xfc/0x128
> [<c0008984>] start_kernel+0x1f8/0x254
> unreferenced object 0xdf8033d0 (size 32):
> comm "swapper", pid 0, jiffies 4294937384
> backtrace:
> [<c00872c0>] kmemleak_alloc+0x144/0x27c
> [<c0085e10>] __kmalloc_track_caller+0x15c/0x194
> [<c0071704>] kstrdup+0x3c/0x58
> [<c009fc5c>] alloc_vfsmnt+0x7c/0x144
> [<c008bc34>] vfs_kern_mount+0x30/0xac
> [<c008bccc>] kern_mount_data+0x1c/0x20
> [<c00104a8>] bdev_cache_init+0x54/0x90
> [<c000fd7c>] vfs_caches_init+0xfc/0x128
> [<c0008984>] start_kernel+0x1f8/0x254
>
> Can this object be freed (as below) or should I just tell kmemleak to
> ignore it (or is it referenced and that's a kmemleak false positive)?
>
>
> diff --git a/fs/block_dev.c b/fs/block_dev.c
> index 349a26c..78e469c 100644
> --- a/fs/block_dev.c
> +++ b/fs/block_dev.c
> @@ -344,6 +344,7 @@ 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);
> }
>
hm, yes, well, we might be able to get away with that - the kernel
holds onto bd_mnt->mnt_sb for internal use for all time, but we don't
directly use that vfsmount for anything after we've constructed
blockdev_superblock.
However there might well be things under blockdev_superblock which point
back at this vfsmount - dunno, I didn't check.
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: Minor kmemleak report via bdev_cache_init
2009-01-12 23:54 ` Andrew Morton
@ 2009-01-13 6:19 ` Cheng Renquan
0 siblings, 0 replies; 3+ messages in thread
From: Cheng Renquan @ 2009-01-13 6:19 UTC (permalink / raw)
To: Andrew Morton; +Cc: Catalin Marinas, linux-kernel, Al Viro
On Tue, Jan 13, 2009 at 7:54 AM, Andrew Morton
<akpm@linux-foundation.org> wrote:
> On Tue, 06 Jan 2009 18:25:34 +0000
> Catalin Marinas <catalin.marinas@arm.com> wrote:
>
>> Hi Denis,
>>
>> With the commit c2acf7b908217 (fs/block_dev.c: __read_mostly improvement
>> and sb_is_blkdev_sb utilization), the bd_mnt is only local and kmemleak
>> reports the corresponding vfsmnt structure as unreferenced (together
>> with the duplicated name) since it can no longer track a valid pointer
>> to it:
>>
>> unreferenced object 0xdf813848 (size 128):
>> comm "swapper", pid 0, jiffies 4294937384
>> backtrace:
>> [<c00872c0>] kmemleak_alloc+0x144/0x27c
>> [<c00848c8>] kmem_cache_alloc+0x108/0x13c
>> [<c009fc00>] alloc_vfsmnt+0x20/0x144
>> [<c008bc34>] vfs_kern_mount+0x30/0xac
>> [<c008bccc>] kern_mount_data+0x1c/0x20
>> [<c00104a8>] bdev_cache_init+0x54/0x90
>> [<c000fd7c>] vfs_caches_init+0xfc/0x128
>> [<c0008984>] start_kernel+0x1f8/0x254
>> unreferenced object 0xdf8033d0 (size 32):
>> comm "swapper", pid 0, jiffies 4294937384
>> backtrace:
>> [<c00872c0>] kmemleak_alloc+0x144/0x27c
>> [<c0085e10>] __kmalloc_track_caller+0x15c/0x194
>> [<c0071704>] kstrdup+0x3c/0x58
>> [<c009fc5c>] alloc_vfsmnt+0x7c/0x144
>> [<c008bc34>] vfs_kern_mount+0x30/0xac
>> [<c008bccc>] kern_mount_data+0x1c/0x20
>> [<c00104a8>] bdev_cache_init+0x54/0x90
>> [<c000fd7c>] vfs_caches_init+0xfc/0x128
>> [<c0008984>] start_kernel+0x1f8/0x254
>>
>> Can this object be freed (as below) or should I just tell kmemleak to
>> ignore it (or is it referenced and that's a kmemleak false positive)?
>>
>>
>> diff --git a/fs/block_dev.c b/fs/block_dev.c
>> index 349a26c..78e469c 100644
>> --- a/fs/block_dev.c
>> +++ b/fs/block_dev.c
>> @@ -344,6 +344,7 @@ 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);
>> }
>
> hm, yes, well, we might be able to get away with that - the kernel
> holds onto bd_mnt->mnt_sb for internal use for all time, but we don't
> directly use that vfsmount for anything after we've constructed
> blockdev_superblock.
>
> However there might well be things under blockdev_superblock which point
> back at this vfsmount - dunno, I didn't check.
I've checked that, the blockdev_superblock doesn't have a back pointer
to vfsmount indeed, and can never use vfsmount anymore, although
generally it needs more testing.
Acked-by: Cheng Renquan <crquan@gmail.com>
To Al Viro: by this checking I found more vfsmount's not used, too, in
some other kern_mount'ed vfsmount, such as pipefs, sockfs, ipc mqueue,
selinux, smackfs, besides bdevfs, in such situations also only
superblock is used, the vfsmount only used as kern_mount and never
used anymore.
So maybe we can do some more cleanup. Patches will be sent later.
--
Denis, Cheng Renquan (程任全), Shenzhen, China
Bob Hope - "I grew up with six brothers. That's how I learned to
dance - waiting for the bathroom."
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2009-01-13 6:20 UTC | newest]
Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2009-01-06 18:25 Minor kmemleak report via bdev_cache_init Catalin Marinas
2009-01-12 23:54 ` Andrew Morton
2009-01-13 6:19 ` Cheng Renquan
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.