On Thu, 18 Nov 2010, Matt Mackall wrote: > > 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? > The leak in ext4_mb_init() above is because it is using kstrdup() to allocate the string itself and then on destroy uses kmem_cache_name() to attain the slub allocator's pointer to the name, not the memory the ext4 layer allocated itself. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom policy in Canada: sign http://dissolvethecrtc.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>