On 8/17/18 5:00 AM, Oscar Salvador wrote: > From: Oscar Salvador <osalvador@xxxxxxx> > > Currently, unregister_mem_sect_under_nodes() tries to allocate a nodemask_t > in order to check whithin the loop which nodes have already been unlinked, > so we do not repeat the operation on them. > > NODEMASK_ALLOC calls kmalloc() if NODES_SHIFT > 8, otherwise > it just declares a nodemask_t variable whithin the stack. > > Since kmalloc() can fail, we actually check whether NODEMASK_ALLOC failed > or not, and we return -ENOMEM accordingly. > remove_memory_section() does not check for the return value though. > It is pretty rare that such a tiny allocation can fail, but if it does, > we will be left with dangled symlinks under /sys/devices/system/node/, > since the mem_blk's directories will be removed no matter what > unregister_mem_sect_under_nodes() returns. > > One way to solve this is to check whether unlinked_nodes is NULL or not. > In the case it is not, we can just use it as before, but if it is NULL, > we can just skip the node_test_and_set check, and call sysfs_remove_link() > unconditionally. > This is harmless as sysfs_remove_link() backs off somewhere down the chain > in case the link has already been removed. > This method was presented in v3 of the path [1]. > > But since the maximum number of nodes we can have is 1024, > when NODES_SHIFT = 10, that gives us a nodemask_t of 128 bytes. > Although everything depends on how deep the stack is, I think we can afford > to define the nodemask_t variable whithin the stack. > > That simplifies the code, and we do not need to worry about untested error > code paths. > > If we see that this causes troubles with the stack, we can always return to [1]. > > Signed-off-by: Oscar Salvador <osalvador@xxxxxxx> LGTM: Reviewed-by: Pavel Tatashin <pavel.tatashin@xxxxxxxxxxxxx> Thank you, Pavel
