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    SubjectRe: [PATCH] slub: operate cache name memory same to slab and slob
    On 18.11.2010 23.15, Matt Mackall wrote:
    > On Thu, 2010-11-18 at 11:00 +0800, b32542@freescale.com wrote:
    >> From: Zeng Zhaoming<zengzm.kernel@gmail.com>
    >>
    >> Get a memory leak complaint about ext4:
    >> comm "mount", pid 1159, jiffies 4294904647 (age 6077.804s)
    >> hex dump (first 32 bytes):
    >> 65 78 74 34 5f 67 72 6f 75 70 69 6e 66 6f 5f 31 ext4_groupinfo_1
    >> 30 00 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b a5 0.kkkkkkkkkkkkk.
    >> backtrace:
    >> [<c068ade3>] kmemleak_alloc+0x93/0xd0
    >> [<c024e54c>] __kmalloc_track_caller+0x30c/0x380
    >> [<c02269d3>] kstrdup+0x33/0x60
    >> [<c0318a70>] ext4_mb_init+0x4e0/0x550
    >> [<c0304e0e>] ext4_fill_super+0x1e6e/0x2f60
    >> [<c0261140>] mount_bdev+0x1c0/0x1f0
    >> [<c02fc00f>] ext4_mount+0x1f/0x30
    >> [<c02603d8>] vfs_kern_mount+0x78/0x250
    >> [<c026060e>] do_kern_mount+0x3e/0x100
    >> [<c027b4c2>] do_mount+0x2e2/0x780
    >> [<c027ba04>] sys_mount+0xa4/0xd0
    >> [<c010429f>] sysenter_do_call+0x12/0x38
    >> [<ffffffff>] 0xffffffff
    >>
    >> It is cause by slub manage the cache name different from slab and slob.
    >> In slab and slob, only reference to name, alloc and reclaim the memory
    >> is the duty of the code that invoked kmem_cache_create().
    >>
    >> In slub, cache name duplicated when create. This ambiguity will cause
    >> some memory leaks and double free if kmem_cache_create() pass a
    >> dynamic malloc cache name.
    >
    > I don't get it.
    >
    > Caller allocates X, passes X to slub, slub duplicates X as X', and
    > properly frees X', then caller frees X. Yes, that's silly, but where's
    > the leak?
    >
    > But slub and slab should obviously both manage names in the same way,
    > namely the historical "caller allocates" way. So:
    >
    > Acked-by: Matt Mackall<mpm@selenic.com>

    The kstrdup() is there because of SLUB cache merging. See commit
    84c1cf62465e2fb0a692620dcfeb52323ab03d48 ("SLUB: Fix merged slab cache
    names") for details.


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