On Mon, Jul 10, 2017 at 12:05:49PM -0700, Shaohua Li wrote: > On Mon, Jul 10, 2017 at 03:25:41PM +0800, Ming Lei wrote: > > On Mon, Jul 10, 2017 at 02:38:19PM +1000, NeilBrown wrote: > > > On Mon, Jul 10 2017, Ming Lei wrote: > > > > > > > On Mon, Jul 10, 2017 at 11:35:12AM +0800, Ming Lei wrote: > > > >> On Mon, Jul 10, 2017 at 7:09 AM, NeilBrown <neilb@xxxxxxxx> wrote: > > > ... > > > >> >> + > > > >> >> + rp->idx = 0; > > > >> > > > > >> > This is the only place the ->idx is initialized, in r1buf_pool_alloc(). > > > >> > The mempool alloc function is suppose to allocate memory, not initialize > > > >> > it. > > > >> > > > > >> > If the mempool_alloc() call cannot allocate memory it will use memory > > > >> > from the pool. If this memory has already been used, then it will no > > > >> > longer have the initialized value. > > > >> > > > > >> > In short: you need to initialise memory *after* calling > > > >> > mempool_alloc(), unless you ensure it is reset to the init values before > > > >> > calling mempool_free(). > > > >> > > > > >> > https://bugzilla.kernel.org/show_bug.cgi?id=196307 > > > >> > > > >> OK, thanks for posting it out. > > > >> > > > >> Another fix might be to reinitialize the variable(rp->idx = 0) in > > > >> r1buf_pool_free(). > > > >> Or just set it as zero every time when it is used. > > > >> > > > >> But I don't understand why mempool_free() calls pool->free() at the end of > > > >> this function, which may cause to run pool->free() on a new allocated buf, > > > >> seems a bug in mempool? > > > > > > > > Looks I missed the 'return' in mempool_free(), so it is fine. > > > > > > > > How about the following fix? > > > > > > It looks like it would probably work, but it is rather unusual to > > > initialise something just before freeing it. > > > > > > Couldn't you just move the initialization to shortly after the > > > mempool_alloc() call. There looks like a good place that already loops > > > over all the bios.... > > > > OK, follows the revised patch according to your suggestion. > > --- > > > > From 68f9936635b3dda13c87a6b6125ac543145bb940 Mon Sep 17 00:00:00 2001 > > From: Ming Lei <ming.lei@xxxxxxxxxx> > > Date: Mon, 10 Jul 2017 15:16:16 +0800 > > Subject: [PATCH] MD: move initialization of resync pages' index out of mempool > > allocator > > > > mempool_alloc() is only responsible for allocation, not for initialization, > > so we need to move the initialization of resync pages's index out of the > > allocator function. > > > > Reported-by: NeilBrown <neilb@xxxxxxxx> > > Fixes: f0250618361d(md: raid10: don't use bio's vec table to manage resync pages) > > Fixes: 98d30c5812c3(md: raid1: don't use bio's vec table to manage resync pages) > > Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxx> > > --- > > drivers/md/raid1.c | 4 +++- > > drivers/md/raid10.c | 6 +++++- > > 2 files changed, 8 insertions(+), 2 deletions(-) > > > > diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c > > index e1a7e3d4c5e4..26f5efba0504 100644 > > --- a/drivers/md/raid1.c > > +++ b/drivers/md/raid1.c > > @@ -170,7 +170,6 @@ static void * r1buf_pool_alloc(gfp_t gfp_flags, void *data) > > resync_get_all_pages(rp); > > } > > > > - rp->idx = 0; > > rp->raid_bio = r1_bio; > > bio->bi_private = rp; > > } > > @@ -2698,6 +2697,9 @@ static sector_t raid1_sync_request(struct mddev *mddev, sector_t sector_nr, > > struct md_rdev *rdev; > > bio = r1_bio->bios[i]; > > > > + /* This initialization should follow mempool_alloc() */ > > + get_resync_pages(bio)->idx = 0; > > + > > This is fragile and hard to maintain. Can we add a wrap for the > allocation/init? The resync pages's index init is done in the following loop after mempool_alloc(), actually the whole loop is still sort of init, so I think it isn't fragile, and it should be fine. -- Ming
