On Mon, Apr 20, 2020 at 3:41 PM Dan Schatzberg <schatzberg.dan@xxxxxxxxx> wrote: > > The memalloc_use_memcg() function to override the default memcg > accounting context currently doesn't nest. But the patches to make the > loop driver cgroup-aware will end up nesting: > > [ 98.137605] alloc_page_buffers+0x210/0x288 > [ 98.141799] __getblk_gfp+0x1d4/0x400 > [ 98.145475] ext4_read_block_bitmap_nowait+0x148/0xbc8 > [ 98.150628] ext4_mb_init_cache+0x25c/0x9b0 > [ 98.154821] ext4_mb_init_group+0x270/0x390 > [ 98.159014] ext4_mb_good_group+0x264/0x270 > [ 98.163208] ext4_mb_regular_allocator+0x480/0x798 > [ 98.168011] ext4_mb_new_blocks+0x958/0x10f8 > [ 98.172294] ext4_ext_map_blocks+0xec8/0x1618 > [ 98.176660] ext4_map_blocks+0x1b8/0x8a0 > [ 98.180592] ext4_writepages+0x830/0xf10 > [ 98.184523] do_writepages+0xb4/0x198 > [ 98.188195] __filemap_fdatawrite_range+0x170/0x1c8 > [ 98.193086] filemap_write_and_wait_range+0x40/0xb0 > [ 98.197974] ext4_punch_hole+0x4a4/0x660 > [ 98.201907] ext4_fallocate+0x294/0x1190 > [ 98.205839] loop_process_work+0x690/0x1100 > [ 98.210032] loop_workfn+0x2c/0x110 > [ 98.213529] process_one_work+0x3e0/0x648 > [ 98.217546] worker_thread+0x70/0x670 > [ 98.221217] kthread+0x1b8/0x1c0 > [ 98.224452] ret_from_fork+0x10/0x18 > > where loop_process_work() sets the memcg override to the memcg that > submitted the IO request, and alloc_page_buffers() sets the override > to the memcg that instantiated the cache page, which may differ. > > Make memalloc_use_memcg() return the old memcg and convert existing > users to a stacking model. Delete the unused memalloc_unuse_memcg(). > > Signed-off-by: Dan Schatzberg <schatzberg.dan@xxxxxxxxx> This patch was from Johannes, so I would suggest to keep his authorship and signoff along with your signoff. Reviewed-by: Shakeel Butt <shakeelb@xxxxxxxxxx>
