Messages in this thread Patch in this message | | | Date | Mon, 12 Jan 2009 15:54:58 -0800 | From | Andrew Morton <> | Subject | Re: Minor kmemleak report via bdev_cache_init |
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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.
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