1 files changed, 438 insertions, 0 deletions
diff --git a/drivers/md/dm-vdo/memory-alloc.c b/drivers/md/dm-vdo/memory-alloc.c
new file mode 100644
index 000000000..185f259c7
--- /dev/null
+++ b/drivers/md/dm-vdo/memory-alloc.c
@@ -0,0 +1,438 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright 2023 Red Hat
+ */
+
+#include <linux/delay.h>
+#include <linux/mm.h>
+#include <linux/sched/mm.h>
+#include <linux/slab.h>
+#include <linux/vmalloc.h>
+
+#include "logger.h"
+#include "memory-alloc.h"
+#include "permassert.h"
+
+/*
+ * UDS and VDO keep track of which threads are allowed to allocate memory freely, and which threads
+ * must be careful to not do a memory allocation that does an I/O request. The 'allocating_threads'
+ * thread_registry and its associated methods implement this tracking.
+ */
+static struct thread_registry allocating_threads;
+
+static inline bool allocations_allowed(void)
+{
+	return vdo_lookup_thread(&allocating_threads) != NULL;
+}
+
+/*
+ * Register the current thread as an allocating thread.
+ *
+ * An optional flag location can be supplied indicating whether, at any given point in time, the
+ * threads associated with that flag should be allocating storage. If the flag is false, a message
+ * will be logged.
+ *
+ * If no flag is supplied, the thread is always allowed to allocate storage without complaint.
+ *
+ * @new_thread: registered_thread structure to use for the current thread
+ * @flag_ptr: Location of the allocation-allowed flag
+ */
+void vdo_register_allocating_thread(struct registered_thread *new_thread,
+				    const bool *flag_ptr)
+{
+	if (flag_ptr == NULL) {
+		static const bool allocation_always_allowed = true;
+
+		flag_ptr = &allocation_always_allowed;
+	}
+
+	vdo_register_thread(&allocating_threads, new_thread, flag_ptr);
+}
+
+/* Unregister the current thread as an allocating thread. */
+void vdo_unregister_allocating_thread(void)
+{
+	vdo_unregister_thread(&allocating_threads);
+}
+
+/*
+ * We track how much memory has been allocated and freed. When we unload the module, we log an
+ * error if we have not freed all the memory that we allocated. Nearly all memory allocation and
+ * freeing is done using this module.
+ *
+ * We do not use kernel functions like the kvasprintf() method, which allocate memory indirectly
+ * using kmalloc.
+ *
+ * These data structures and methods are used to track the amount of memory used.
+ */
+
+/*
+ * We allocate very few large objects, and allocation/deallocation isn't done in a
+ * performance-critical stage for us, so a linked list should be fine.
+ */
+struct vmalloc_block_info {
+	void *ptr;
+	size_t size;
+	struct vmalloc_block_info *next;
+};
+
+static struct {
+	spinlock_t lock;
+	size_t kmalloc_blocks;
+	size_t kmalloc_bytes;
+	size_t vmalloc_blocks;
+	size_t vmalloc_bytes;
+	size_t peak_bytes;
+	struct vmalloc_block_info *vmalloc_list;
+} memory_stats __cacheline_aligned;
+
+static void update_peak_usage(void)
+{
+	size_t total_bytes = memory_stats.kmalloc_bytes + memory_stats.vmalloc_bytes;
+
+	if (total_bytes > memory_stats.peak_bytes)
+		memory_stats.peak_bytes = total_bytes;
+}
+
+static void add_kmalloc_block(size_t size)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(&memory_stats.lock, flags);
+	memory_stats.kmalloc_blocks++;
+	memory_stats.kmalloc_bytes += size;
+	update_peak_usage();
+	spin_unlock_irqrestore(&memory_stats.lock, flags);
+}
+
+static void remove_kmalloc_block(size_t size)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(&memory_stats.lock, flags);
+	memory_stats.kmalloc_blocks--;
+	memory_stats.kmalloc_bytes -= size;
+	spin_unlock_irqrestore(&memory_stats.lock, flags);
+}
+
+static void add_vmalloc_block(struct vmalloc_block_info *block)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(&memory_stats.lock, flags);
+	block->next = memory_stats.vmalloc_list;
+	memory_stats.vmalloc_list = block;
+	memory_stats.vmalloc_blocks++;
+	memory_stats.vmalloc_bytes += block->size;
+	update_peak_usage();
+	spin_unlock_irqrestore(&memory_stats.lock, flags);
+}
+
+static void remove_vmalloc_block(void *ptr)
+{
+	struct vmalloc_block_info *block;
+	struct vmalloc_block_info **block_ptr;
+	unsigned long flags;
+
+	spin_lock_irqsave(&memory_stats.lock, flags);
+	for (block_ptr = &memory_stats.vmalloc_list;
+	     (block = *block_ptr) != NULL;
+	     block_ptr = &block->next) {
+		if (block->ptr == ptr) {
+			*block_ptr = block->next;
+			memory_stats.vmalloc_blocks--;
+			memory_stats.vmalloc_bytes -= block->size;
+			break;
+		}
+	}
+
+	spin_unlock_irqrestore(&memory_stats.lock, flags);
+	if (block != NULL)
+		vdo_free(block);
+	else
+		vdo_log_info("attempting to remove ptr %px not found in vmalloc list", ptr);
+}
+
+/*
+ * Determine whether allocating a memory block should use kmalloc or __vmalloc.
+ *
+ * vmalloc can allocate any integral number of pages.
+ *
+ * kmalloc can allocate any number of bytes up to a configured limit, which defaults to 8 megabytes
+ * on some systems. kmalloc is especially good when memory is being both allocated and freed, and
+ * it does this efficiently in a multi CPU environment.
+ *
+ * kmalloc usually rounds the size of the block up to the next power of two, so when the requested
+ * block is bigger than PAGE_SIZE / 2 bytes, kmalloc will never give you less space than the
+ * corresponding vmalloc allocation. Sometimes vmalloc will use less overhead than kmalloc.
+ *
+ * The advantages of kmalloc do not help out UDS or VDO, because we allocate all our memory up
+ * front and do not free and reallocate it. Sometimes we have problems using kmalloc, because the
+ * Linux memory page map can become so fragmented that kmalloc will not give us a 32KB chunk. We
+ * have used vmalloc as a backup to kmalloc in the past, and a follow-up vmalloc of 32KB will work.
+ * But there is no strong case to be made for using kmalloc over vmalloc for these size chunks.
+ *
+ * The kmalloc/vmalloc boundary is set at 4KB, and kmalloc gets the 4KB requests. There is no
+ * strong reason for favoring either kmalloc or vmalloc for 4KB requests, except that tracking
+ * vmalloc statistics uses a linked list implementation. Using a simple test, this choice of
+ * boundary results in 132 vmalloc calls. Using vmalloc for requests of exactly 4KB results in an
+ * additional 6374 vmalloc calls, which is much less efficient for tracking.
+ *
+ * @size: How many bytes to allocate
+ */
+static inline bool use_kmalloc(size_t size)
+{
+	return size <= PAGE_SIZE;
+}
+
+/*
+ * Allocate storage based on memory size and alignment, logging an error if the allocation fails.
+ * The memory will be zeroed.
+ *
+ * @size: The size of an object
+ * @align: The required alignment
+ * @what: What is being allocated (for error logging)
+ * @ptr: A pointer to hold the allocated memory
+ *
+ * Return: VDO_SUCCESS or an error code
+ */
+int vdo_allocate_memory(size_t size, size_t align, const char *what, void *ptr)
+{
+	/*
+	 * The __GFP_RETRY_MAYFAIL flag means the VM implementation will retry memory reclaim
+	 * procedures that have previously failed if there is some indication that progress has
+	 * been made elsewhere. It can wait for other tasks to attempt high level approaches to
+	 * freeing memory such as compaction (which removes fragmentation) and page-out. There is
+	 * still a definite limit to the number of retries, but it is a larger limit than with
+	 * __GFP_NORETRY. Allocations with this flag may fail, but only when there is genuinely
+	 * little unused memory. While these allocations do not directly trigger the OOM killer,
+	 * their failure indicates that the system is likely to need to use the OOM killer soon.
+	 * The caller must handle failure, but can reasonably do so by failing a higher-level
+	 * request, or completing it only in a much less efficient manner.
+	 */
+	const gfp_t gfp_flags = GFP_KERNEL | __GFP_ZERO | __GFP_RETRY_MAYFAIL;
+	unsigned int noio_flags;
+	bool allocations_restricted = !allocations_allowed();
+	unsigned long start_time;
+	void *p = NULL;
+
+	if (unlikely(ptr == NULL))
+		return -EINVAL;
+
+	if (size == 0) {
+		*((void **) ptr) = NULL;
+		return VDO_SUCCESS;
+	}
+
+	if (allocations_restricted)
+		noio_flags = memalloc_noio_save();
+
+	start_time = jiffies;
+	if (use_kmalloc(size) && (align < PAGE_SIZE)) {
+		p = kmalloc(size, gfp_flags | __GFP_NOWARN);
+		if (p == NULL) {
+			/*
+			 * It is possible for kmalloc to fail to allocate memory because there is
+			 * no page available. A short sleep may allow the page reclaimer to
+			 * free a page.
+			 */
+			fsleep(1000);
+			p = kmalloc(size, gfp_flags);
+		}
+
+		if (p != NULL)
+			add_kmalloc_block(ksize(p));
+	} else {
+		struct vmalloc_block_info *block;
+
+		if (vdo_allocate(1, struct vmalloc_block_info, __func__, &block) == VDO_SUCCESS) {
+			/*
+			 * It is possible for __vmalloc to fail to allocate memory because there
+			 * are no pages available. A short sleep may allow the page reclaimer
+			 * to free enough pages for a small allocation.
+			 *
+			 * For larger allocations, the page_alloc code is racing against the page
+			 * reclaimer. If the page reclaimer can stay ahead of page_alloc, the
+			 * __vmalloc will succeed. But if page_alloc overtakes the page reclaimer,
+			 * the allocation fails. It is possible that more retries will succeed.
+			 */
+			for (;;) {
+				p = __vmalloc(size, gfp_flags | __GFP_NOWARN);
+				if (p != NULL)
+					break;
+
+				if (jiffies_to_msecs(jiffies - start_time) > 1000) {
+					/* Try one more time, logging a failure for this call. */
+					p = __vmalloc(size, gfp_flags);
+					break;
+				}
+
+				fsleep(1000);
+			}
+
+			if (p == NULL) {
+				vdo_free(block);
+			} else {
+				block->ptr = p;
+				block->size = PAGE_ALIGN(size);
+				add_vmalloc_block(block);
+			}
+		}
+	}
+
+	if (allocations_restricted)
+		memalloc_noio_restore(noio_flags);
+
+	if (unlikely(p == NULL)) {
+		vdo_log_error("Could not allocate %zu bytes for %s in %u msecs",
+			      size, what, jiffies_to_msecs(jiffies - start_time));
+		return -ENOMEM;
+	}
+
+	*((void **) ptr) = p;
+	return VDO_SUCCESS;
+}
+
+/*
+ * Allocate storage based on memory size, failing immediately if the required memory is not
+ * available. The memory will be zeroed.
+ *
+ * @size: The size of an object.
+ * @what: What is being allocated (for error logging)
+ *
+ * Return: pointer to the allocated memory, or NULL if the required space is not available.
+ */
+void *vdo_allocate_memory_nowait(size_t size, const char *what __maybe_unused)
+{
+	void *p = kmalloc(size, GFP_NOWAIT | __GFP_ZERO);
+
+	if (p != NULL)
+		add_kmalloc_block(ksize(p));
+
+	return p;
+}
+
+void vdo_free(void *ptr)
+{
+	if (ptr != NULL) {
+		if (is_vmalloc_addr(ptr)) {
+			remove_vmalloc_block(ptr);
+			vfree(ptr);
+		} else {
+			remove_kmalloc_block(ksize(ptr));
+			kfree(ptr);
+		}
+	}
+}
+
+/*
+ * Reallocate dynamically allocated memory. There are no alignment guarantees for the reallocated
+ * memory. If the new memory is larger than the old memory, the new space will be zeroed.
+ *
+ * @ptr: The memory to reallocate.
+ * @old_size: The old size of the memory
+ * @size: The new size to allocate
+ * @what: What is being allocated (for error logging)
+ * @new_ptr: A pointer to hold the reallocated pointer
+ *
+ * Return: VDO_SUCCESS or an error code
+ */
+int vdo_reallocate_memory(void *ptr, size_t old_size, size_t size, const char *what,
+			  void *new_ptr)
+{
+	int result;
+
+	if (size == 0) {
+		vdo_free(ptr);
+		*(void **) new_ptr = NULL;
+		return VDO_SUCCESS;
+	}
+
+	result = vdo_allocate(size, char, what, new_ptr);
+	if (result != VDO_SUCCESS)
+		return result;
+
+	if (ptr != NULL) {
+		if (old_size < size)
+			size = old_size;
+
+		memcpy(*((void **) new_ptr), ptr, size);
+		vdo_free(ptr);
+	}
+
+	return VDO_SUCCESS;
+}
+
+int vdo_duplicate_string(const char *string, const char *what, char **new_string)
+{
+	int result;
+	u8 *dup;
+
+	result = vdo_allocate(strlen(string) + 1, u8, what, &dup);
+	if (result != VDO_SUCCESS)
+		return result;
+
+	memcpy(dup, string, strlen(string) + 1);
+	*new_string = dup;
+	return VDO_SUCCESS;
+}
+
+void vdo_memory_init(void)
+{
+	spin_lock_init(&memory_stats.lock);
+	vdo_initialize_thread_registry(&allocating_threads);
+}
+
+void vdo_memory_exit(void)
+{
+	VDO_ASSERT_LOG_ONLY(memory_stats.kmalloc_bytes == 0,
+			    "kmalloc memory used (%zd bytes in %zd blocks) is returned to the kernel",
+			    memory_stats.kmalloc_bytes, memory_stats.kmalloc_blocks);
+	VDO_ASSERT_LOG_ONLY(memory_stats.vmalloc_bytes == 0,
+			    "vmalloc memory used (%zd bytes in %zd blocks) is returned to the kernel",
+			    memory_stats.vmalloc_bytes, memory_stats.vmalloc_blocks);
+	vdo_log_debug("peak usage %zd bytes", memory_stats.peak_bytes);
+}
+
+void vdo_get_memory_stats(u64 *bytes_used, u64 *peak_bytes_used)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(&memory_stats.lock, flags);
+	*bytes_used = memory_stats.kmalloc_bytes + memory_stats.vmalloc_bytes;
+	*peak_bytes_used = memory_stats.peak_bytes;
+	spin_unlock_irqrestore(&memory_stats.lock, flags);
+}
+
+/*
+ * Report stats on any allocated memory that we're tracking. Not all allocation types are
+ * guaranteed to be tracked in bytes (e.g., bios).
+ */
+void vdo_report_memory_usage(void)
+{
+	unsigned long flags;
+	u64 kmalloc_blocks;
+	u64 kmalloc_bytes;
+	u64 vmalloc_blocks;
+	u64 vmalloc_bytes;
+	u64 peak_usage;
+	u64 total_bytes;
+
+	spin_lock_irqsave(&memory_stats.lock, flags);
+	kmalloc_blocks = memory_stats.kmalloc_blocks;
+	kmalloc_bytes = memory_stats.kmalloc_bytes;
+	vmalloc_blocks = memory_stats.vmalloc_blocks;
+	vmalloc_bytes = memory_stats.vmalloc_bytes;
+	peak_usage = memory_stats.peak_bytes;
+	spin_unlock_irqrestore(&memory_stats.lock, flags);
+	total_bytes = kmalloc_bytes + vmalloc_bytes;
+	vdo_log_info("current module memory tracking (actual allocation sizes, not requested):");
+	vdo_log_info("  %llu bytes in %llu kmalloc blocks",
+		     (unsigned long long) kmalloc_bytes,
+		     (unsigned long long) kmalloc_blocks);
+	vdo_log_info("  %llu bytes in %llu vmalloc blocks",
+		     (unsigned long long) vmalloc_bytes,
+		     (unsigned long long) vmalloc_blocks);
+	vdo_log_info("  total %llu bytes, peak usage %llu bytes",
+		     (unsigned long long) total_bytes, (unsigned long long) peak_usage);
+}