[dpdk-dev] [PATCH] mem: fix free segment when using huge-unlink option

[dpdk-dev] [PATCH] mem: fix free segment when using huge-unlink option

[Roy Shterman]

When using huge_unlink we unlink the segment right
after allocation. Although we unlink the file we keep
the fd in fd_list so file still exist just the path deleted.
When freeing the hugepage we need to close the fd and assign
it with (-1) in fd_list for the page to be released.

The current flow fails rte_malloc in the following flow when working
with --huge-unlink option:
1. alloc_seg() for segment A -
    We allocate segment, unlink the path to the segment
    and keep the file descriptor in fd_list.
2. free_seg() for segment A -
    We clear the segment metadata and return - without closing fd
    or assigning (-1) in fd list.
3. alloc_seg() for segment A again -
    We find segment A as available, try to allocate it,
    find the old fd in fd_list try to unlink it
    as part of alloc_seg() but failed because path doesn't exist.

The impact of such error is falsly failing rte_malloc()
although we have hugepages available.

Fixes: d435aad37da7 ("mem: support --huge-unlink mode")

Signed-off-by: Roy Shterman <roy.shterman@vastdata.com>
---
 lib/librte_eal/linux/eal_memalloc.c | 14 ++------------
 1 file changed, 2 insertions(+), 12 deletions(-)

diff --git a/lib/librte_eal/linux/eal_memalloc.c b/lib/librte_eal/linux/eal_memalloc.c
index 6dc1b2bae..c590d6043 100644
--- a/lib/librte_eal/linux/eal_memalloc.c
+++ b/lib/librte_eal/linux/eal_memalloc.c
@@ -709,7 +709,6 @@ free_seg(struct rte_memseg *ms, struct hugepage_info *hi,
 	uint64_t map_offset;
 	char path[PATH_MAX];
 	int fd, ret = 0;
-	bool exit_early;
 	const struct internal_config *internal_conf =
 		eal_get_internal_configuration();
 
@@ -725,17 +724,8 @@ free_seg(struct rte_memseg *ms, struct hugepage_info *hi,
 
 	eal_mem_set_dump(ms->addr, ms->len, false);
 
-	exit_early = false;
-
 	/* if we're using anonymous hugepages, nothing to be done */
-	if (internal_conf->in_memory && !memfd_create_supported)
-		exit_early = true;
-
-	/* if we've already unlinked the page, nothing needs to be done */
-	if (!internal_conf->in_memory && internal_conf->hugepage_unlink)
-		exit_early = true;
-
-	if (exit_early) {
+	if (internal_conf->in_memory && !memfd_create_supported) {
 		memset(ms, 0, sizeof(*ms));
 		return 0;
 	}
@@ -761,7 +751,7 @@ free_seg(struct rte_memseg *ms, struct hugepage_info *hi,
 		/* if we're able to take out a write lock, we're the last one
 		 * holding onto this page.
 		 */
-		if (!internal_conf->in_memory) {
+		if (!internal_conf->in_memory && !internal_conf->hugepage_unlink) {
 			ret = lock(fd, LOCK_EX);
 			if (ret >= 0) {
 				/* no one else is using this page */
-- 
2.24.1

Re: [dpdk-dev] [PATCH] mem: fix free segment when using huge-unlink option

[Burakov, Anatoly]

On 22-Feb-21 10:41 AM, Roy Shterman wrote:
> When using huge_unlink we unlink the segment right
> after allocation. Although we unlink the file we keep
> the fd in fd_list so file still exist just the path deleted.
> When freeing the hugepage we need to close the fd and assign
> it with (-1) in fd_list for the page to be released.
> 
> The current flow fails rte_malloc in the following flow when working
> with --huge-unlink option:
> 1. alloc_seg() for segment A -
>      We allocate segment, unlink the path to the segment
>      and keep the file descriptor in fd_list.
> 2. free_seg() for segment A -
>      We clear the segment metadata and return - without closing fd
>      or assigning (-1) in fd list.
> 3. alloc_seg() for segment A again -
>      We find segment A as available, try to allocate it,
>      find the old fd in fd_list try to unlink it
>      as part of alloc_seg() but failed because path doesn't exist.
> 
> The impact of such error is falsly failing rte_malloc()
> although we have hugepages available.
> 
> Fixes: d435aad37da7 ("mem: support --huge-unlink mode")
> 
> Signed-off-by: Roy Shterman <roy.shterman@vastdata.com>

Cc: stable@dpdk.org

Provisionally, patch looks fine, but i'll have to have a closer look.

-- 
Thanks,
Anatoly

Re: [dpdk-dev] [PATCH] mem: fix free segment when using huge-unlink option

[Roy Shterman]

On Mon, Feb 22, 2021 at 5:53 PM Burakov, Anatoly <anatoly.burakov@intel.com>
wrote:

> On 22-Feb-21 10:41 AM, Roy Shterman wrote:
> > When using huge_unlink we unlink the segment right
> > after allocation. Although we unlink the file we keep
> > the fd in fd_list so file still exist just the path deleted.
> > When freeing the hugepage we need to close the fd and assign
> > it with (-1) in fd_list for the page to be released.
> >
> > The current flow fails rte_malloc in the following flow when working
> > with --huge-unlink option:
> > 1. alloc_seg() for segment A -
> >      We allocate segment, unlink the path to the segment
> >      and keep the file descriptor in fd_list.
> > 2. free_seg() for segment A -
> >      We clear the segment metadata and return - without closing fd
> >      or assigning (-1) in fd list.
> > 3. alloc_seg() for segment A again -
> >      We find segment A as available, try to allocate it,
> >      find the old fd in fd_list try to unlink it
> >      as part of alloc_seg() but failed because path doesn't exist.
> >
> > The impact of such error is falsly failing rte_malloc()
> > although we have hugepages available.
> >
> > Fixes: d435aad37da7 ("mem: support --huge-unlink mode")
> >
> > Signed-off-by: Roy Shterman <roy.shterman@vastdata.com>
>
> Cc: stable@dpdk.org
>
> Provisionally, patch looks fine, but i'll have to have a closer look.
>

Hi Anatoly,

Do I need to send this patch also to stable or it will happen automatically
if the patch will reach the next release candidate?
Also I wonder if you had more time to review this one?


>
> --
> Thanks,
> Anatoly
>

Thanks,
Roy

Re: [dpdk-dev] [PATCH] mem: fix free segment when using huge-unlink option

[Burakov, Anatoly]

On 28-Feb-21 1:21 PM, Roy Shterman wrote:
> 
> 
> On Mon, Feb 22, 2021 at 5:53 PM Burakov, Anatoly 
> <anatoly.burakov@intel.com <mailto:anatoly.burakov@intel.com>> wrote:
> 
>     On 22-Feb-21 10:41 AM, Roy Shterman wrote:
>      > When using huge_unlink we unlink the segment right
>      > after allocation. Although we unlink the file we keep
>      > the fd in fd_list so file still exist just the path deleted.
>      > When freeing the hugepage we need to close the fd and assign
>      > it with (-1) in fd_list for the page to be released.
>      >
>      > The current flow fails rte_malloc in the following flow when working
>      > with --huge-unlink option:
>      > 1. alloc_seg() for segment A -
>      >      We allocate segment, unlink the path to the segment
>      >      and keep the file descriptor in fd_list.
>      > 2. free_seg() for segment A -
>      >      We clear the segment metadata and return - without closing fd
>      >      or assigning (-1) in fd list.
>      > 3. alloc_seg() for segment A again -
>      >      We find segment A as available, try to allocate it,
>      >      find the old fd in fd_list try to unlink it
>      >      as part of alloc_seg() but failed because path doesn't exist.
>      >
>      > The impact of such error is falsly failing rte_malloc()
>      > although we have hugepages available.
>      >
>      > Fixes: d435aad37da7 ("mem: support --huge-unlink mode")
>      >
>      > Signed-off-by: Roy Shterman <roy.shterman@vastdata.com
>     <mailto:roy.shterman@vastdata.com>>
> 
>     Cc: stable@dpdk.org <mailto:stable@dpdk.org>
> 
>     Provisionally, patch looks fine, but i'll have to have a closer look.
> 
> 
> Hi Anatoly,
> 
> Do I need to send this patch also to stable or it will happen 
> automatically if the patch will reach the next release candidate?

Not automatically, generally you should add a CC to stable for the patch 
to be considered as part of stable release. That said, usually Fixed: 
tag is also used to determine whether a patch is backport-able, so 
having a correctly identified Fixed: tag is a mandatory minimum :)

> Also I wonder if you had more time to review this one?

Not yet, but i'll try to make some time this week.

> 
> 
>     -- 
>     Thanks,
>     Anatoly
> 
> 
> Thanks,
> Roy


-- 
Thanks,
Anatoly

Re: [dpdk-dev] [dpdk-stable] [PATCH] mem: fix free segment when using huge-unlink option

[David Marchand]

Hello,

On Mon, Mar 1, 2021 at 11:44 AM Burakov, Anatoly
<anatoly.burakov@intel.com> wrote:
>
> On 28-Feb-21 1:21 PM, Roy Shterman wrote:
> >
> >
> > On Mon, Feb 22, 2021 at 5:53 PM Burakov, Anatoly
> > <anatoly.burakov@intel.com <mailto:anatoly.burakov@intel.com>> wrote:
> >
> >     On 22-Feb-21 10:41 AM, Roy Shterman wrote:
> >      > When using huge_unlink we unlink the segment right
> >      > after allocation. Although we unlink the file we keep
> >      > the fd in fd_list so file still exist just the path deleted.
> >      > When freeing the hugepage we need to close the fd and assign
> >      > it with (-1) in fd_list for the page to be released.
> >      >
> >      > The current flow fails rte_malloc in the following flow when working
> >      > with --huge-unlink option:
> >      > 1. alloc_seg() for segment A -
> >      >      We allocate segment, unlink the path to the segment
> >      >      and keep the file descriptor in fd_list.
> >      > 2. free_seg() for segment A -
> >      >      We clear the segment metadata and return - without closing fd
> >      >      or assigning (-1) in fd list.
> >      > 3. alloc_seg() for segment A again -
> >      >      We find segment A as available, try to allocate it,
> >      >      find the old fd in fd_list try to unlink it
> >      >      as part of alloc_seg() but failed because path doesn't exist.
> >      >
> >      > The impact of such error is falsly failing rte_malloc()
> >      > although we have hugepages available.
> >      >
> >      > Fixes: d435aad37da7 ("mem: support --huge-unlink mode")
> >      >
> >      > Signed-off-by: Roy Shterman <roy.shterman@vastdata.com
> >     <mailto:roy.shterman@vastdata.com>>
> >
> >     Cc: stable@dpdk.org <mailto:stable@dpdk.org>
> >
> >     Provisionally, patch looks fine, but i'll have to have a closer look.
> >
> >
> > Hi Anatoly,
> >
> > Do I need to send this patch also to stable or it will happen
> > automatically if the patch will reach the next release candidate?
>
> Not automatically, generally you should add a CC to stable for the patch
> to be considered as part of stable release. That said, usually Fixed:
> tag is also used to determine whether a patch is backport-able, so
> having a correctly identified Fixed: tag is a mandatory minimum :)
>
> > Also I wonder if you had more time to review this one?
>
> Not yet, but i'll try to make some time this week.

Any update?

Thanks.


-- 
David Marchand

Re: [dpdk-dev] [PATCH] mem: fix free segment when using huge-unlink option

[Burakov, Anatoly]

On 22-Feb-21 10:41 AM, Roy Shterman wrote:
> When using huge_unlink we unlink the segment right
> after allocation. Although we unlink the file we keep
> the fd in fd_list so file still exist just the path deleted.
> When freeing the hugepage we need to close the fd and assign
> it with (-1) in fd_list for the page to be released.
> 
> The current flow fails rte_malloc in the following flow when working
> with --huge-unlink option:
> 1. alloc_seg() for segment A -
>      We allocate segment, unlink the path to the segment
>      and keep the file descriptor in fd_list.
> 2. free_seg() for segment A -
>      We clear the segment metadata and return - without closing fd
>      or assigning (-1) in fd list.
> 3. alloc_seg() for segment A again -
>      We find segment A as available, try to allocate it,
>      find the old fd in fd_list try to unlink it
>      as part of alloc_seg() but failed because path doesn't exist.
> 
> The impact of such error is falsly failing rte_malloc()
> although we have hugepages available.
> 
> Fixes: d435aad37da7 ("mem: support --huge-unlink mode")
> 
> Signed-off-by: Roy Shterman <roy.shterman@vastdata.com>
> ---

Acked-by: Anatoly Burakov <anatoly.burakov@intel.com>

-- 
Thanks,
Anatoly

Re: [dpdk-dev] [PATCH] mem: fix free segment when using huge-unlink option

[David Marchand]

On Thu, Apr 1, 2021 at 1:07 PM Burakov, Anatoly
<anatoly.burakov@intel.com> wrote:
>
> On 22-Feb-21 10:41 AM, Roy Shterman wrote:
> > When using huge_unlink we unlink the segment right
> > after allocation. Although we unlink the file we keep
> > the fd in fd_list so file still exist just the path deleted.
> > When freeing the hugepage we need to close the fd and assign
> > it with (-1) in fd_list for the page to be released.
> >
> > The current flow fails rte_malloc in the following flow when working
> > with --huge-unlink option:
> > 1. alloc_seg() for segment A -
> >      We allocate segment, unlink the path to the segment
> >      and keep the file descriptor in fd_list.
> > 2. free_seg() for segment A -
> >      We clear the segment metadata and return - without closing fd
> >      or assigning (-1) in fd list.
> > 3. alloc_seg() for segment A again -
> >      We find segment A as available, try to allocate it,
> >      find the old fd in fd_list try to unlink it
> >      as part of alloc_seg() but failed because path doesn't exist.
> >
> > The impact of such error is falsly failing rte_malloc()
falsely*

> > although we have hugepages available.
> >
> > Fixes: d435aad37da7 ("mem: support --huge-unlink mode")
Cc: stable@dpdk.org

> >
> > Signed-off-by: Roy Shterman <roy.shterman@vastdata.com>
> Acked-by: Anatoly Burakov <anatoly.burakov@intel.com>

Applied, thanks.


-- 
David Marchand