On 11/24/2014 02:08 PM, Dexuan Cui wrote: >> -----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. If I read the code correctly, if part of 2M allocation fails. alloc_balloon_pages() will have a non zero return value with alloc_error set. Then it will match the following check: if ((alloc_error) || (num_ballooned == num_pages)) { which will set done to true. So there's no second iteration of while (!done) loop? Probably you need something like: if ((alloc_unit != 1) && (num_ballooned == 0)) { alloc_unit = 1; continue; } if ((alloc_unit == 1) || (num_ballooned = num_pages)) { ... } _______________________________________________ devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxx http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel
