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-rw-r--r--fs/erofs/pcpubuf.c148
1 files changed, 148 insertions, 0 deletions
diff --git a/fs/erofs/pcpubuf.c b/fs/erofs/pcpubuf.c
new file mode 100644
index 0000000000..c7a4b1d770
--- /dev/null
+++ b/fs/erofs/pcpubuf.c
@@ -0,0 +1,148 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) Gao Xiang <xiang@kernel.org>
+ *
+ * For low-latency decompression algorithms (e.g. lz4), reserve consecutive
+ * per-CPU virtual memory (in pages) in advance to store such inplace I/O
+ * data if inplace decompression is failed (due to unmet inplace margin for
+ * example).
+ */
+#include "internal.h"
+
+struct erofs_pcpubuf {
+ raw_spinlock_t lock;
+ void *ptr;
+ struct page **pages;
+ unsigned int nrpages;
+};
+
+static DEFINE_PER_CPU(struct erofs_pcpubuf, erofs_pcb);
+
+void *erofs_get_pcpubuf(unsigned int requiredpages)
+ __acquires(pcb->lock)
+{
+ struct erofs_pcpubuf *pcb = &get_cpu_var(erofs_pcb);
+
+ raw_spin_lock(&pcb->lock);
+ /* check if the per-CPU buffer is too small */
+ if (requiredpages > pcb->nrpages) {
+ raw_spin_unlock(&pcb->lock);
+ put_cpu_var(erofs_pcb);
+ /* (for sparse checker) pretend pcb->lock is still taken */
+ __acquire(pcb->lock);
+ return NULL;
+ }
+ return pcb->ptr;
+}
+
+void erofs_put_pcpubuf(void *ptr) __releases(pcb->lock)
+{
+ struct erofs_pcpubuf *pcb = &per_cpu(erofs_pcb, smp_processor_id());
+
+ DBG_BUGON(pcb->ptr != ptr);
+ raw_spin_unlock(&pcb->lock);
+ put_cpu_var(erofs_pcb);
+}
+
+/* the next step: support per-CPU page buffers hotplug */
+int erofs_pcpubuf_growsize(unsigned int nrpages)
+{
+ static DEFINE_MUTEX(pcb_resize_mutex);
+ static unsigned int pcb_nrpages;
+ struct page *pagepool = NULL;
+ int delta, cpu, ret, i;
+
+ mutex_lock(&pcb_resize_mutex);
+ delta = nrpages - pcb_nrpages;
+ ret = 0;
+ /* avoid shrinking pcpubuf, since no idea how many fses rely on */
+ if (delta <= 0)
+ goto out;
+
+ for_each_possible_cpu(cpu) {
+ struct erofs_pcpubuf *pcb = &per_cpu(erofs_pcb, cpu);
+ struct page **pages, **oldpages;
+ void *ptr, *old_ptr;
+
+ pages = kmalloc_array(nrpages, sizeof(*pages), GFP_KERNEL);
+ if (!pages) {
+ ret = -ENOMEM;
+ break;
+ }
+
+ for (i = 0; i < nrpages; ++i) {
+ pages[i] = erofs_allocpage(&pagepool, GFP_KERNEL);
+ if (!pages[i]) {
+ ret = -ENOMEM;
+ oldpages = pages;
+ goto free_pagearray;
+ }
+ }
+ ptr = vmap(pages, nrpages, VM_MAP, PAGE_KERNEL);
+ if (!ptr) {
+ ret = -ENOMEM;
+ oldpages = pages;
+ goto free_pagearray;
+ }
+ raw_spin_lock(&pcb->lock);
+ old_ptr = pcb->ptr;
+ pcb->ptr = ptr;
+ oldpages = pcb->pages;
+ pcb->pages = pages;
+ i = pcb->nrpages;
+ pcb->nrpages = nrpages;
+ raw_spin_unlock(&pcb->lock);
+
+ if (!oldpages) {
+ DBG_BUGON(old_ptr);
+ continue;
+ }
+
+ if (old_ptr)
+ vunmap(old_ptr);
+free_pagearray:
+ while (i)
+ erofs_pagepool_add(&pagepool, oldpages[--i]);
+ kfree(oldpages);
+ if (ret)
+ break;
+ }
+ pcb_nrpages = nrpages;
+ erofs_release_pages(&pagepool);
+out:
+ mutex_unlock(&pcb_resize_mutex);
+ return ret;
+}
+
+void __init erofs_pcpubuf_init(void)
+{
+ int cpu;
+
+ for_each_possible_cpu(cpu) {
+ struct erofs_pcpubuf *pcb = &per_cpu(erofs_pcb, cpu);
+
+ raw_spin_lock_init(&pcb->lock);
+ }
+}
+
+void erofs_pcpubuf_exit(void)
+{
+ int cpu, i;
+
+ for_each_possible_cpu(cpu) {
+ struct erofs_pcpubuf *pcb = &per_cpu(erofs_pcb, cpu);
+
+ if (pcb->ptr) {
+ vunmap(pcb->ptr);
+ pcb->ptr = NULL;
+ }
+ if (!pcb->pages)
+ continue;
+
+ for (i = 0; i < pcb->nrpages; ++i)
+ if (pcb->pages[i])
+ put_page(pcb->pages[i]);
+ kfree(pcb->pages);
+ pcb->pages = NULL;
+ }
+}