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Date: Fri, 21 Aug 2015 16:20:52 +0200
From: Vlastimil Babka <vbabka@...e.cz>
To: Mel Gorman <mgorman@...hsingularity.net>,
Linux-MM <linux-mm@...ck.org>
Cc: Johannes Weiner <hannes@...xchg.org>,
Rik van Riel <riel@...hat.com>,
David Rientjes <rientjes@...gle.com>,
Joonsoo Kim <iamjoonsoo.kim@....com>,
Michal Hocko <mhocko@...nel.org>,
LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 07/10] mm: page_alloc: Rename __GFP_WAIT to __GFP_RECLAIM
On 08/12/2015 12:45 PM, Mel Gorman wrote:
> __GFP_WAIT was used to signal that the caller was in atomic context and
> could not sleep. Now it is possible to distinguish between true atomic
> context and callers that are not willing to sleep. The latter should clear
> __GFP_DIRECT_RECLAIM so kswapd will still wake. As clearing __GFP_WAIT
> behaves differently, there is a risk that people will clear the wrong
> flags. This patch renames __GFP_WAIT to __GFP_RECLAIM to clearly indicate
> what it does -- setting it allows all reclaim activity, clearing them
> prevents it.
>
> Signed-off-by: Mel Gorman <mgorman@...hsingularity.net>
...
> diff --git a/drivers/block/drbd/drbd_receiver.c b/drivers/block/drbd/drbd_receiver.c
> index c097909c589c..1d2046e68808 100644
> --- a/drivers/block/drbd/drbd_receiver.c
> +++ b/drivers/block/drbd/drbd_receiver.c
> @@ -357,7 +357,7 @@ drbd_alloc_peer_req(struct drbd_peer_device *peer_device, u64 id, sector_t secto
> }
>
> if (has_payload && data_size) {
> - page = drbd_alloc_pages(peer_device, nr_pages, (gfp_mask & __GFP_WAIT));
> + page = drbd_alloc_pages(peer_device, nr_pages, (gfp_mask & __GFP_RECLAIM));
I think here it should test only for direct reclaim (via the helper) and
thus moved to patch 06?
> --- a/drivers/gpu/drm/i915/i915_gem.c
> +++ b/drivers/gpu/drm/i915/i915_gem.c
> @@ -2226,7 +2226,7 @@ i915_gem_object_get_pages_gtt(struct drm_i915_gem_object *obj)
> mapping = file_inode(obj->base.filp)->i_mapping;
> gfp = mapping_gfp_mask(mapping);
> gfp |= __GFP_NORETRY | __GFP_NOWARN;
> - gfp &= ~(__GFP_IO | __GFP_WAIT);
> + gfp &= ~(__GFP_IO | __GFP_RECLAIM);
Why clear the kswapd reclaim here?
> diff --git a/drivers/staging/lustre/include/linux/libcfs/libcfs_private.h b/drivers/staging/lustre/include/linux/libcfs/libcfs_private.h
> index ed37d26eb20d..393270436a4b 100644
> --- a/drivers/staging/lustre/include/linux/libcfs/libcfs_private.h
> +++ b/drivers/staging/lustre/include/linux/libcfs/libcfs_private.h
> @@ -113,7 +113,7 @@ do { \
> do { \
> LASSERT(!in_interrupt() || \
> ((size) <= LIBCFS_VMALLOC_SIZE && \
> - ((mask) & __GFP_WAIT) == 0)); \
> + ((mask) & __GFP_RECLAIM) == 0)); \
> } while (0)
This should test only __GFP_DIRECT_RECLAIM?
> #define LIBCFS_ALLOC_POST(ptr, size) \
> diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
> index 35660da77921..92e284d0362e 100644
> --- a/fs/btrfs/extent_io.c
> +++ b/fs/btrfs/extent_io.c
> @@ -718,7 +718,7 @@ int clear_extent_bit(struct extent_io_tree *tree, u64 start, u64 end,
> if (start > end)
> goto out;
> spin_unlock(&tree->lock);
> - if (mask & __GFP_WAIT)
> + if (mask & __GFP_RECLAIM)
> cond_resched();
> goto again;
> }
> @@ -1028,7 +1028,7 @@ __set_extent_bit(struct extent_io_tree *tree, u64 start, u64 end,
> if (start > end)
> goto out;
> spin_unlock(&tree->lock);
> - if (mask & __GFP_WAIT)
> + if (mask & __GFP_RECLAIM)
> cond_resched();
> goto again;
> }
> @@ -1253,7 +1253,7 @@ int convert_extent_bit(struct extent_io_tree *tree, u64 start, u64 end,
> if (start > end)
> goto out;
> spin_unlock(&tree->lock);
> - if (mask & __GFP_WAIT)
> + if (mask & __GFP_RECLAIM)
> cond_resched();
> first_iteration = false;
> goto again;
This too?
> diff --git a/include/linux/gfp.h b/include/linux/gfp.h
> index dbd246a14e2f..e066f3afae73 100644
> --- a/include/linux/gfp.h
> +++ b/include/linux/gfp.h
> @@ -104,7 +104,7 @@ struct vm_area_struct;
> * can be cleared when the reclaiming of pages would cause unnecessary
> * disruption.
> */
> -#define __GFP_WAIT (__GFP_DIRECT_RECLAIM|__GFP_KSWAPD_RECLAIM)
> +#define __GFP_RECLAIM (__GFP_DIRECT_RECLAIM|__GFP_KSWAPD_RECLAIM)
> #define __GFP_DIRECT_RECLAIM ((__force gfp_t)___GFP_DIRECT_RECLAIM) /* Caller can reclaim */
> #define __GFP_KSWAPD_RECLAIM ((__force gfp_t)___GFP_KSWAPD_RECLAIM) /* kswapd can wake */
>
> @@ -123,12 +123,12 @@ struct vm_area_struct;
> */
> #define GFP_ATOMIC (__GFP_HIGH|__GFP_ATOMIC|__GFP_KSWAPD_RECLAIM)
> #define GFP_NOWAIT (__GFP_KSWAPD_RECLAIM)
> -#define GFP_NOIO (__GFP_WAIT)
> -#define GFP_NOFS (__GFP_WAIT | __GFP_IO)
> -#define GFP_KERNEL (__GFP_WAIT | __GFP_IO | __GFP_FS)
> -#define GFP_TEMPORARY (__GFP_WAIT | __GFP_IO | __GFP_FS | \
> +#define GFP_NOIO (__GFP_RECLAIM)
> +#define GFP_NOFS (__GFP_RECLAIM | __GFP_IO)
> +#define GFP_KERNEL (__GFP_RECLAIM | __GFP_IO | __GFP_FS)
> +#define GFP_TEMPORARY (__GFP_RECLAIM | __GFP_IO | __GFP_FS | \
> __GFP_RECLAIMABLE)
> -#define GFP_USER (__GFP_WAIT | __GFP_IO | __GFP_FS | __GFP_HARDWALL)
> +#define GFP_USER (__GFP_RECLAIM | __GFP_IO | __GFP_FS | __GFP_HARDWALL)
> #define GFP_HIGHUSER (GFP_USER | __GFP_HIGHMEM)
> #define GFP_HIGHUSER_MOVABLE (GFP_HIGHUSER | __GFP_MOVABLE)
> #define GFP_IOFS (__GFP_IO | __GFP_FS)
Hmm GFP_IOFS should maybe include __GFP_KSWAPD_RECLAIM? Although I
wonder if it makes sense to use it like "... | GFP_IOFS" and not just as
a mask "... & ~GFP_IOFS". Not including __GFP_KSWAPD_RECLAIM changes the
former use, while including it changes the latter one.
Maybe we should just remove it while at it? There's only a handful of
users. mm/ uses it as a mask, and the rest is in staging/lustre and it's
doing allocations like "__GFP_ZERO | GFP_IOFS" which looks like a
mistake to me - what good is IO or FS without DIRECT_RECLAIM?
It's probably best we removed it or changed it to __GFP_IOFS. The form
without underscores suggests usage as parameter to alloc functions and
that's clearly wrong here.
> diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
> index d8e2e3918ce2..4bee2392dbb2 100644
> --- a/net/netlink/af_netlink.c
> +++ b/net/netlink/af_netlink.c
> @@ -2061,7 +2061,7 @@ int netlink_broadcast_filtered(struct sock *ssk, struct sk_buff *skb, u32 portid
> consume_skb(info.skb2);
>
> if (info.delivered) {
> - if (info.congested && (allocation & __GFP_WAIT))
> + if (info.congested && (allocation & __GFP_RECLAIM))
> yield();
Just direct reclaim?
> return 0;
> }
> diff --git a/net/rxrpc/ar-connection.c b/net/rxrpc/ar-connection.c
> index 6631f4f1e39b..b5cd65401a28 100644
> --- a/net/rxrpc/ar-connection.c
> +++ b/net/rxrpc/ar-connection.c
> @@ -500,7 +500,7 @@ int rxrpc_connect_call(struct rxrpc_sock *rx,
> if (bundle->num_conns >= 20) {
> _debug("too many conns");
>
> - if (!(gfp & __GFP_WAIT)) {
> + if (!(gfp & __GFP_RECLAIM)) {
> _leave(" = -EAGAIN");
> return -EAGAIN;
> }
ditto?
--
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