On 18.11.2010 23.15, Matt Mackall wrote:
On Thu, 2010-11-18 at 11:00 +0800, b32542@xxxxxxxxxxxxx wrote:From: Zeng Zhaoming<zengzm.kernel@xxxxxxxxx> 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@xxxxxxxxxxx>
The kstrdup() is there because of SLUB cache merging. See commit 84c1cf62465e2fb0a692620dcfeb52323ab03d48 ("SLUB: Fix merged slab cache names") for details.
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