> -----Original Message----- > From: Jason Wang [mailto:jasowang@xxxxxxxxxx] > Sent: Monday, November 24, 2014 13:18 PM > To: Dexuan Cui; gregkh@xxxxxxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; > driverdev-devel@xxxxxxxxxxxxxxxxxxxxxx; olaf@xxxxxxxxx; > apw@xxxxxxxxxxxxx; KY Srinivasan > Cc: Haiyang Zhang > Subject: Re: [PATCH] hv: hv_balloon: avoid memory leak on alloc_error of > 2MB memory block > > On 11/24/2014 01:56 PM, Dexuan Cui wrote: > > If num_ballooned is not 0, we shouldn't neglect the already-allocated > 2MB > > memory block(s). > > > > Cc: K. Y. Srinivasan <kys@xxxxxxxxxxxxx> > > Cc: <stable@xxxxxxxxxxxxxxx> > > Signed-off-by: Dexuan Cui <decui@xxxxxxxxxxxxx> > > --- > > drivers/hv/hv_balloon.c | 4 +++- > > 1 file changed, 3 insertions(+), 1 deletion(-) > > > > diff --git a/drivers/hv/hv_balloon.c b/drivers/hv/hv_balloon.c > > index 5e90c5d..cba2d3b 100644 > > --- a/drivers/hv/hv_balloon.c > > +++ b/drivers/hv/hv_balloon.c > > @@ -1091,6 +1091,8 @@ static void balloon_up(struct work_struct > *dummy) > > bool done = false; > > int i; > > > > + /* The host does balloon_up in 2MB. */ > > + WARN_ON(num_pages % PAGES_IN_2M != 0); > > > > /* > > * We will attempt 2M allocations. However, if we fail to > > @@ -1111,7 +1113,7 @@ static void balloon_up(struct work_struct > *dummy) > > bl_resp, alloc_unit, > > &alloc_error); > > > > - if ((alloc_error) && (alloc_unit != 1)) { > > + if (alloc_error && (alloc_unit != 1) && num_ballooned == 0) > { > > alloc_unit = 1; > > continue; > > } > > Before the change, we may retry the 4K allocation when part or all 2M > allocations were failed. This makes sense when memory is fragmented. But Yes, but all the partially-allocated 2MB memory blocks are lost(mem leak). > after the change, if part of 2M allocation were failed, we won't retry > 4K allocation. Is this expected? Hi Jason, The patch doesn't break the "try 2MB first; then try 4K" logic: With the change, we'll retry the 2MB allocation in the next iteration of the same while (!done) loop -- we expect this retry will cause "alloc_error && (alloc_unit != 1) && num_ballooned == 0" to be true, so we'll later try 4K allocation, as we did before. > Btw, can host just require 1M? If yes, should alloc_balloon_pages() set Hi KY, Can you please clarify this? You know the host much more than me. :-) > alloc_error if num_pages < alloc_unit for caller to catch this and retry > 4K allocation? -- Dexuan _______________________________________________ devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxx http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel
