From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mike Rapoport Subject: Re: [PATCH 6/6] mm: Add memalloc_nowait Date: Mon, 29 Jun 2020 08:08:51 +0300 Message-ID: <20200629050851.GC1492837@kernel.org> References: <20200625113122.7540-1-willy@infradead.org> <20200625113122.7540-7-willy@infradead.org> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20200625113122.7540-7-willy@infradead.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: dm-devel-bounces@redhat.com Errors-To: dm-devel-bounces@redhat.com Content-Disposition: inline To: "Matthew Wilcox (Oracle)" Cc: Jens Axboe , linux-kernel@vger.kernel.org, linux-xfs@vger.kernel.org, linux-mm@kvack.org, dm-devel@redhat.com, Mikulas Patocka List-Id: dm-devel.ids On Thu, Jun 25, 2020 at 12:31:22PM +0100, Matthew Wilcox (Oracle) wrote: > Similar to memalloc_noio() and memalloc_nofs(), memalloc_nowait() > guarantees we will not sleep to reclaim memory. Use it to simplify > dm-bufio's allocations. > > Signed-off-by: Matthew Wilcox (Oracle) > --- > drivers/md/dm-bufio.c | 30 ++++++++---------------------- > include/linux/sched.h | 1 + > include/linux/sched/mm.h | 12 ++++++++---- > 3 files changed, 17 insertions(+), 26 deletions(-) > > diff --git a/drivers/md/dm-bufio.c b/drivers/md/dm-bufio.c > index 6d1565021d74..140ada9a2c8f 100644 > --- a/drivers/md/dm-bufio.c > +++ b/drivers/md/dm-bufio.c > @@ -412,23 +412,6 @@ static void *alloc_buffer_data(struct dm_bufio_client *c, gfp_t gfp_mask, > > *data_mode = DATA_MODE_VMALLOC; > > - /* > - * __vmalloc allocates the data pages and auxiliary structures with > - * gfp_flags that were specified, but pagetables are always allocated > - * with GFP_KERNEL, no matter what was specified as gfp_mask. > - * > - * Consequently, we must set per-process flag PF_MEMALLOC_NOIO so that > - * all allocations done by this process (including pagetables) are done > - * as if GFP_NOIO was specified. > - */ > - if (gfp_mask & __GFP_NORETRY) { > - unsigned noio_flag = memalloc_noio_save(); > - void *ptr = __vmalloc(c->block_size, gfp_mask); > - > - memalloc_noio_restore(noio_flag); > - return ptr; > - } > - > return __vmalloc(c->block_size, gfp_mask); > } > > @@ -866,9 +849,6 @@ static struct dm_buffer *__alloc_buffer_wait_no_callback(struct dm_bufio_client > * dm-bufio is resistant to allocation failures (it just keeps > * one buffer reserved in cases all the allocations fail). > * So set flags to not try too hard: > - * GFP_NOWAIT: don't wait; if we need to sleep we'll release our > - * mutex and wait ourselves. > - * __GFP_NORETRY: don't retry and rather return failure > * __GFP_NOMEMALLOC: don't use emergency reserves > * __GFP_NOWARN: don't print a warning in case of failure > * > @@ -877,7 +857,9 @@ static struct dm_buffer *__alloc_buffer_wait_no_callback(struct dm_bufio_client > */ > while (1) { > if (dm_bufio_cache_size_latch != 1) { > - b = alloc_buffer(c, GFP_NOWAIT | __GFP_NORETRY | __GFP_NOMEMALLOC | __GFP_NOWARN); > + unsigned nowait_flag = memalloc_nowait_save(); > + b = alloc_buffer(c, GFP_KERNEL | __GFP_NOMEMALLOC | __GFP_NOWARN); > + memalloc_nowait_restore(nowait_flag); > if (b) > return b; > } > @@ -886,8 +868,12 @@ static struct dm_buffer *__alloc_buffer_wait_no_callback(struct dm_bufio_client > return NULL; > > if (dm_bufio_cache_size_latch != 1 && !tried_noio_alloc) { > + unsigned noio_flag; > + > dm_bufio_unlock(c); > - b = alloc_buffer(c, GFP_NOIO | __GFP_NORETRY | __GFP_NOMEMALLOC | __GFP_NOWARN); > + noio_flag = memalloc_noio_save(); I've read the series twice and I'm still missing the definition of memalloc_noio_save(). And also it would be nice to have a paragraph about it in Documentation/core-api/memory-allocation.rst > + b = alloc_buffer(c, GFP_KERNEL | > __GFP_NOMEMALLOC | __GFP_NOWARN); + > memalloc_noio_restore(noio_flag); dm_bufio_lock(c); if (b) > return b; > diff --git a/include/linux/sched.h b/include/linux/sched.h > index 90336850e940..b1c2cddd366c 100644 > --- a/include/linux/sched.h > +++ b/include/linux/sched.h > @@ -803,6 +803,7 @@ struct task_struct { > #endif > unsigned memalloc_noio:1; > unsigned memalloc_nofs:1; > + unsigned memalloc_nowait:1; > unsigned memalloc_nocma:1; > > unsigned long atomic_flags; /* Flags requiring atomic access. */ > diff --git a/include/linux/sched/mm.h b/include/linux/sched/mm.h > index 6f7b59a848a6..6484569f50df 100644 > --- a/include/linux/sched/mm.h > +++ b/include/linux/sched/mm.h > @@ -179,12 +179,16 @@ static inline bool in_vfork(struct task_struct *tsk) > static inline gfp_t current_gfp_context(gfp_t flags) > { > if (unlikely(current->memalloc_noio || current->memalloc_nofs || > - current->memalloc_nocma)) { > + current->memalloc_nocma) || current->memalloc_nowait) { > /* > - * NOIO implies both NOIO and NOFS and it is a weaker context > - * so always make sure it makes precedence > + * Clearing DIRECT_RECLAIM means we won't get to the point > + * of testing IO or FS, so we don't need to bother clearing > + * them. noio implies neither IO nor FS and it is a weaker > + * context so always make sure it takes precedence. > */ > - if (current->memalloc_noio) > + if (current->memalloc_nowait) > + flags &= ~__GFP_DIRECT_RECLAIM; > + else if (current->memalloc_noio) > flags &= ~(__GFP_IO | __GFP_FS); > else if (current->memalloc_nofs) > flags &= ~__GFP_FS; > -- > 2.27.0 > > -- Sincerely yours, Mike.