percpu: restructure pcpu_extend_area_map() to fix bugs and improve readability (833af842) · Commits · 戴 / test

mm/percpu.c

+81 −40

Original line number	Diff line number	Diff line
		@@ -355,62 +355,86 @@ static struct pcpu_chunk pcpu_chunk_addr_search(void addr)
		}

		/**
		* pcpu_extend_area_map - extend area map for allocation
		* @chunk: target chunk
		* pcpu_need_to_extend - determine whether chunk area map needs to be extended
		* @chunk: chunk of interest
		*
		* Extend area map of @chunk so that it can accomodate an allocation.
		* A single allocation can split an area into three areas, so this
		* function makes sure that @chunk->map has at least two extra slots.
		* Determine whether area map of @chunk needs to be extended to
		* accomodate a new allocation.
		*
		* CONTEXT:
		* pcpu_alloc_mutex, pcpu_lock. pcpu_lock is released and reacquired
		* if area map is extended.
		* pcpu_lock.
		*
		* RETURNS:
		* 0 if noop, 1 if successfully extended, -errno on failure.
		* New target map allocation length if extension is necessary, 0
		* otherwise.
		*/
		static int pcpu_extend_area_map(struct pcpu_chunk chunk, unsigned long flags)
		static int pcpu_need_to_extend(struct pcpu_chunk *chunk)
		{
		int new_alloc;
		int *new;
		size_t size;

		/* has enough? */
		if (chunk->map_alloc >= chunk->map_used + 2)
		return 0;

		spin_unlock_irqrestore(&pcpu_lock, *flags);

		new_alloc = PCPU_DFL_MAP_ALLOC;
		while (new_alloc < chunk->map_used + 2)
		new_alloc *= 2;

		new = pcpu_mem_alloc(new_alloc * sizeof(new[0]));
		if (!new) {
		spin_lock_irqsave(&pcpu_lock, *flags);
		return -ENOMEM;
		return new_alloc;
		}

		/*
		* Acquire pcpu_lock and switch to new area map. Only free
		* could have happened inbetween, so map_used couldn't have
		* grown.
		/**
		* pcpu_extend_area_map - extend area map of a chunk
		* @chunk: chunk of interest
		* @new_alloc: new target allocation length of the area map
		*
		* Extend area map of @chunk to have @new_alloc entries.
		*
		* CONTEXT:
		* Does GFP_KERNEL allocation. Grabs and releases pcpu_lock.
		*
		* RETURNS:
		* 0 on success, -errno on failure.
		*/
		spin_lock_irqsave(&pcpu_lock, *flags);
		BUG_ON(new_alloc < chunk->map_used + 2);
		static int pcpu_extend_area_map(struct pcpu_chunk *chunk, int new_alloc)
		{
		int old = NULL, new = NULL;
		size_t old_size = 0, new_size = new_alloc * sizeof(new[0]);
		unsigned long flags;

		new = pcpu_mem_alloc(new_size);
		if (!new)
		return -ENOMEM;

		size = chunk->map_alloc * sizeof(chunk->map[0]);
		memcpy(new, chunk->map, size);
		/* acquire pcpu_lock and switch to new area map */
		spin_lock_irqsave(&pcpu_lock, flags);

		if (new_alloc <= chunk->map_alloc)
		goto out_unlock;

		old_size = chunk->map_alloc * sizeof(chunk->map[0]);
		memcpy(new, chunk->map, old_size);

		/*
		* map_alloc < PCPU_DFL_MAP_ALLOC indicates that the chunk is
		* one of the first chunks and still using static map.
		*/
		if (chunk->map_alloc >= PCPU_DFL_MAP_ALLOC)
		pcpu_mem_free(chunk->map, size);
		old = chunk->map;

		chunk->map_alloc = new_alloc;
		chunk->map = new;
		new = NULL;

		out_unlock:
		spin_unlock_irqrestore(&pcpu_lock, flags);

		/*
		* pcpu_mem_free() might end up calling vfree() which uses
		* IRQ-unsafe lock and thus can't be called under pcpu_lock.
		*/
		pcpu_mem_free(old, old_size);
		pcpu_mem_free(new, new_size);

		return 0;
		}

		@@ -1049,7 +1073,7 @@ static void *pcpu_alloc(size_t size, size_t align, bool reserved)
		static int warn_limit = 10;
		struct pcpu_chunk *chunk;
		const char *err;
		int slot, off;
		int slot, off, new_alloc;
		unsigned long flags;

		if (unlikely(!size \|\| size > PCPU_MIN_UNIT_SIZE \|\| align > PAGE_SIZE)) {
		@@ -1064,14 +1088,25 @@ static void *pcpu_alloc(size_t size, size_t align, bool reserved)
		/* serve reserved allocations from the reserved chunk if available */
		if (reserved && pcpu_reserved_chunk) {
		chunk = pcpu_reserved_chunk;
		if (size > chunk->contig_hint \|\|
		pcpu_extend_area_map(chunk, &flags) < 0) {
		err = "failed to extend area map of reserved chunk";

		if (size > chunk->contig_hint) {
		err = "alloc from reserved chunk failed";
		goto fail_unlock;
		}

		while ((new_alloc = pcpu_need_to_extend(chunk))) {
		spin_unlock_irqrestore(&pcpu_lock, flags);
		if (pcpu_extend_area_map(chunk, new_alloc) < 0) {
		err = "failed to extend area map of reserved chunk";
		goto fail_unlock_mutex;
		}
		spin_lock_irqsave(&pcpu_lock, flags);
		}

		off = pcpu_alloc_area(chunk, size, align);
		if (off >= 0)
		goto area_found;

		err = "alloc from reserved chunk failed";
		goto fail_unlock;
		}
		@@ -1083,14 +1118,20 @@ restart:
		if (size > chunk->contig_hint)
		continue;

		switch (pcpu_extend_area_map(chunk, &flags)) {
		case 0:
		break;
		case 1:
		goto restart; /* pcpu_lock dropped, restart */
		default:
		new_alloc = pcpu_need_to_extend(chunk);
		if (new_alloc) {
		spin_unlock_irqrestore(&pcpu_lock, flags);
		if (pcpu_extend_area_map(chunk,
		new_alloc) < 0) {
		err = "failed to extend area map";
		goto fail_unlock;
		goto fail_unlock_mutex;
		}
		spin_lock_irqsave(&pcpu_lock, flags);
		/*
		* pcpu_lock has been dropped, need to
		* restart cpu_slot list walking.
		*/
		goto restart;
		}

		off = pcpu_alloc_area(chunk, size, align);

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