I tested a patched bcache module. OK for me. Le 09/06/2019 à 17:28, Coly Li a écrit :
On 2019/6/9 11:24 下午, Coly Li wrote:Recently people report bcache code compiled with gcc9 is broken, one of the buggy behavior I observe is that two adjacent 4KB I/Os should merge into one but they don't. Finally it turns out to be a stack corruption caused by macro PRECEDING_KEY(). See how PRECEDING_KEY() is defined in bset.h, 437 #define PRECEDING_KEY(_k) \ 438 ({ \ 439 struct bkey *_ret = NULL; \ 440 \ 441 if (KEY_INODE(_k) || KEY_OFFSET(_k)) { \ 442 _ret = &KEY(KEY_INODE(_k), KEY_OFFSET(_k), 0); \ 443 \ 444 if (!_ret->low) \ 445 _ret->high--; \ 446 _ret->low--; \ 447 } \ 448 \ 449 _ret; \ 450 }) At line 442, _ret points to address of a on-stack variable combined by KEY(), the life range of this on-stack variable is in line 442-446, once _ret is returned to bch_btree_insert_key(), the returned address points to an invalid stack address and this address is overwritten in the following called bch_btree_iter_init(). Then argument 'search' of bch_btree_iter_init() points to some address inside stackframe of bch_btree_iter_init(), exact address depends on how the compiler allocates stack space. Now the stack is corrupted. Signed-off-by: Coly Li <colyli@xxxxxxx> Reviewed-by: Rolf Fokkens <rolf@xxxxxxxxxxxxxx> Reviewed-by: Pierre JUHEN <pierre.juhen@xxxxxxxxx>Hi Rolf and Pierre, Oops, I am a little bit too hurry, just realize you don't offer Reviewed-by: yet. Could you like to offer a Reviewed-by: to this patch, then I may submit to Jens in this run ASAP. Many thanks of your code review and help ! Coly LiTested-by: Shenghui Wang <shhuiw@xxxxxxxxxxx> Cc: Kent Overstreet <kent.overstreet@xxxxxxxxx> Cc: Nix <nix@xxxxxxxxxxxxx> --- Changlog: V2: Fix a pointer assignment problem in preceding_key(), which is pointed by Rolf Fokkens and Pierre JUHEN. V1: Initial RFC patch for review and comment. drivers/md/bcache/bset.c | 16 +++++++++++++--- drivers/md/bcache/bset.h | 34 ++++++++++++++++++++-------------- 2 files changed, 33 insertions(+), 17 deletions(-)[snipped]
