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https://github.com/Mathewnd/Astral.git
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vmmcache: initial implementation
This commit is contained in:
Matheus
@@ -0,0 +1,316 @@
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#include <kernel/vmmcache.h>
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#include <kernel/vmm.h>
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#include <util.h>
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#include <logging.h>
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#define TABLE_SIZE 4096
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#define WRITER_TICK_SECONDS 1
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static mutex_t mutex;
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static page_t **table;
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static thread_t *writerthread;
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static semaphore_t sync;
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#define HOLD_LOCK() \
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MUTEX_ACQUIRE(&mutex, false);
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#define RELEASE_LOCK() \
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MUTEX_RELEASE(&mutex);
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static inline uint64_t fnv1ahash(void *buffer, size_t size);
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static uintmax_t getentry(vnode_t *vnode, uintmax_t offset) {
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struct {
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vnode_t *vnode;
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uintmax_t offset;
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} tmp;
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tmp.vnode = vnode;
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tmp.offset = offset;
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return fnv1ahash(&tmp, sizeof(tmp)) % TABLE_SIZE;
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}
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// assumes lock is held
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static page_t *findpage(vnode_t *vnode, uintmax_t offset) {
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uintmax_t entry = getentry(vnode, offset);
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page_t *page = table[entry];
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while (page) {
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if (page->backing == vnode && page->offset == offset)
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break;
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page = page->hashnext;
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}
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return page;
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}
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// assumes lock is held
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static void putpage(page_t *page) {
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uintmax_t entry = getentry(page->backing, page->offset);
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// add to table list
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page->hashprev = NULL;
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page->hashnext = table[entry];
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if (table[entry])
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table[entry]->hashprev = page;
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table[entry] = page;
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// add to vnode list
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// XXX this could be a bit slow if a large portion of the file is in memory and it gets purged
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page->vnodeprev = NULL;
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page->vnodenext = page->backing->pages;
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if (page->backing->pages)
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page->backing->pages->vnodeprev = page;
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page->backing->pages = page;
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}
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// assumes lock is held
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static void removepage(page_t *page) {
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uintmax_t entry = getentry(page->backing, page->offset);
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// remove from table list
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if (page->hashnext)
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page->hashnext->hashprev = page->hashprev;
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if (page->hashprev)
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page->hashprev->hashnext = page->hashnext;
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else
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table[entry] = page->hashnext;
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page->hashnext = NULL;
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page->hashprev = NULL;
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// remove from vnode list
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if (page->vnodenext)
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page->vnodenext->vnodeprev = page->vnodeprev;
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if (page->vnodeprev)
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page->vnodeprev->vnodenext = page->vnodenext;
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else
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page->backing->pages = page->vnodenext;
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page->vnodenext = NULL;
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page->vnodeprev = NULL;
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}
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int vmmcache_getpage(vnode_t *vnode, uintmax_t offset, page_t **res) {
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__assert(vnode->type == V_TYPE_REGULAR || vnode->type == V_TYPE_BLKDEV);
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__assert((offset % PAGE_SIZE) == 0);
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retry_err:
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HOLD_LOCK();
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page_t *newpage = NULL;
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volatile page_t *page = findpage(vnode, offset);
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retry:
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if (page) {
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// page is present in the page cache
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pmm_hold(pmm_getpageaddress((page_t *)page));
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RELEASE_LOCK();
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// in the case of a retry, release the allocated page here
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if (newpage)
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pmm_release(newpage);
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// wait for page to be ready
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while ((page->flags & (PAGE_FLAGS_READY | PAGE_FLAGS_ERROR)) == 0)
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sched_yield(); // TODO proper sleeping mechanism here
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if (page->flags & PAGE_FLAGS_ERROR) {
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// the thread handling the page in failed to read it, we should retry it and see whats up
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pmm_release((page_t *)page);
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goto retry_err;
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}
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*res = (page_t *)page;
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} else {
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// page is not present in the cache, we will have to load it in
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RELEASE_LOCK();
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void *address = pmm_allocpage(PMM_SECTION_DEFAULT);
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if (address == NULL)
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return ENOMEM;
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newpage = pmm_getpage(address);
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HOLD_LOCK();
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// while the lock wasn't being held, the page could have potentially been added to the cache
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// check for it again and return from the function as if it was always there in the first place
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page = findpage(vnode, offset);
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if (page)
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goto retry;
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newpage->backing = vnode;
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newpage->offset = offset;
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// add it to the page cache
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putpage(newpage);
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RELEASE_LOCK();
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int error = VOP_GETPAGE(vnode, offset, newpage);
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// TODO wake up the sleeping threads when implemented
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if (error) {
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// an error happened with GETPAGE, remove the page from the cache,
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// tell the sleeping threads that something happened and free the page
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// by setting backing to null so it gets treated as an anonymous page again
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HOLD_LOCK();
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removepage(newpage);
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newpage->flags |= PAGE_FLAGS_ERROR;
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newpage->backing = NULL;
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newpage->offset = 0;
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RELEASE_LOCK();
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pmm_release(newpage);
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return error;
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}
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newpage->flags |= PAGE_FLAGS_READY;
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*res = newpage;
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}
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RELEASE_LOCK();
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return 0;
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}
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int vmmcache_takepage(page_t *page) {
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HOLD_LOCK();
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// someone called vmmcache_getpage() and got this page while the lock wasn't held
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// return an error status to the caller
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if (page->refcount > 1) {
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RELEASE_LOCK();
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return EAGAIN;
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}
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__assert(page->refcount == 1);
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__assert((page->flags & PAGE_FLAGS_DIRTY) == 0);
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// XXX maybe just not allow truncated pages to take up space like this?
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if ((page->flags & PAGE_FLAGS_TRUNCATED) == 0) {
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// the page needs to be removed from the cache to continue
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removepage(page);
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}
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RELEASE_LOCK();
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return 0;
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}
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int vmmcache_truncate(vnode_t *vnode, uintmax_t offset) {
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HOLD_LOCK();
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page_t *pagelist = NULL;
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page_t *page = vnode->pages;
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while (page) {
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page_t *oldpage = page;
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page = page->vnodenext;
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// only truncate past a certain offset
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if (oldpage->offset < offset)
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continue;
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oldpage->flags |= PAGE_FLAGS_TRUNCATED;
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removepage(oldpage);
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oldpage->vnodenext = pagelist;
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pagelist = oldpage;
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}
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RELEASE_LOCK();
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// make sure to unref if they are pinned
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while (pagelist) {
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page_t *page = pagelist;
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pagelist = pagelist->vnodenext;
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if (page->flags & PAGE_FLAGS_PINNED)
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pmm_release(pmm_getpageaddress(page));
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}
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return 0;
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}
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int vmmcache_syncvnode(vnode_t *vnode) {
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__assert(!"unimplemented");
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}
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int vmmcache_sync() {
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semaphore_signal(&sync);
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return 0;
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}
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static page_t *dirtylist;
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int vmmcache_makedirty(page_t *page) {
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HOLD_LOCK();
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if ((page->flags & (PAGE_FLAGS_DIRTY | PAGE_FLAGS_TRUNCATED)) == 0) {
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// page is neither dirty nor truncated, add to dirty list and hold the page and vnode
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page->flags |= PAGE_FLAGS_DIRTY;
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page->writeprev = NULL;
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page->writenext = dirtylist;
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if (dirtylist)
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dirtylist->writeprev = page;
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dirtylist = page;
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pmm_hold(pmm_getpageaddress(page));
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__assert(page->backing);
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VOP_HOLD(page->backing);
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}
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RELEASE_LOCK();
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return 0;
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}
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static void tick(context_t *, dpcarg_t arg) {
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vmmcache_sync();
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}
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static void writer() {
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timerentry_t timerentry;
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// this will be inserted on some random cpu's timer, but it will always work after that
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interrupt_set(false);
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timer_insert(_cpu()->timer, &timerentry, tick, NULL, (uintmax_t)WRITER_TICK_SECONDS * 1000000, true);
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interrupt_set(true);
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for (;;) {
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HOLD_LOCK();
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// TODO make FIFO rather than LIFO
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volatile page_t *page = dirtylist;
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if (page == NULL) {
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RELEASE_LOCK();
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semaphore_wait(&sync, false);
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continue;
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}
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__assert(page->flags & PAGE_FLAGS_DIRTY);
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page->flags &= ~PAGE_FLAGS_DIRTY;
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dirtylist = page->writenext;
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if (dirtylist)
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dirtylist->writeprev = NULL;
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page->writenext = NULL;
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RELEASE_LOCK();
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if ((page->flags & PAGE_FLAGS_TRUNCATED) == 0) {
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VOP_PUTPAGE(page->backing, page->offset, (page_t *)page);
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VOP_RELEASE(page->backing);
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}
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pmm_release(pmm_getpageaddress((page_t *)page));
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}
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}
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void vmmcache_init() {
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MUTEX_INIT(&mutex);
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table = vmm_map(NULL, TABLE_SIZE * sizeof(page_t *), VMM_FLAGS_ALLOCATE, ARCH_MMU_FLAGS_READ | ARCH_MMU_FLAGS_WRITE | ARCH_MMU_FLAGS_NOEXEC, NULL);
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__assert(table);
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memset(table, 0, TABLE_SIZE * sizeof(page_t *));
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SEMAPHORE_INIT(&sync, 0);
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writerthread = sched_newthread(writer, PAGE_SIZE * 4, 1, NULL, NULL);
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__assert(writerthread);
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sched_queue(writerthread);
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vmmcache_sync();
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}
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