Mount by running
sudo mount -t BasicMFS BasicMFS -o numpages=<pages> <mntdir>
Where <pages> is the max number of 4KB pages it can use, and <mntdir> is
the directory to mount the filesystem to.
This patch is meant to serve as a reference for the reviewers and is not
intended to be upstreamed.
Signed-off-by: Bijan Tabatabai <btabatabai@xxxxxxxx>
---
BasicMFS/Kconfig | 3 +
BasicMFS/Makefile | 8 +
BasicMFS/basic.c | 717 ++++++++++++++++++++++++++++++++++++++++++++++
BasicMFS/basic.h | 29 ++
4 files changed, 757 insertions(+)
create mode 100644 BasicMFS/Kconfig
create mode 100644 BasicMFS/Makefile
create mode 100644 BasicMFS/basic.c
create mode 100644 BasicMFS/basic.h
diff --git a/BasicMFS/Kconfig b/BasicMFS/Kconfig
new file mode 100644
index 000000000000..3b536eded0ed
--- /dev/null
+++ b/BasicMFS/Kconfig
@@ -0,0 +1,3 @@
+config BASICMMFS
+ tristate "Adds the BasicMMFS"
+ default m
diff --git a/BasicMFS/Makefile b/BasicMFS/Makefile
new file mode 100644
index 000000000000..e50d27819c3c
--- /dev/null
+++ b/BasicMFS/Makefile
@@ -0,0 +1,8 @@
+obj-m += basicmfs.o
+basicmfs-y += basic.o
+
+all:
+ make -C ../kbuild M=$(PWD) modules
+
+clean:
+ make -C ../kbuild M=$(PWD) clean
diff --git a/BasicMFS/basic.c b/BasicMFS/basic.c
new file mode 100644
index 000000000000..88490de64db4
--- /dev/null
+++ b/BasicMFS/basic.c
@@ -0,0 +1,717 @@
+#include <linux/kernel.h>
+#include <linux/mm.h>
+#include <linux/mman.h>
+#include <linux/gfp.h>
+#include <linux/fs_context.h>
+#include <linux/fs_parser.h>
+#include <linux/pagemap.h>
+#include <linux/statfs.h>
+#include <linux/module.h>
+#include <linux/rmap.h>
+#include <linux/string.h>
+#include <linux/falloc.h>
+#include <linux/pagewalk.h>
+#include <linux/file_based_mm.h>
+#include <linux/swap.h>
+#include <linux/swapops.h>
+#include <linux/pagevec.h>
+
+#include <asm/tlbflush.h>
+
+#include "basic.h"
+
+static const struct super_operations basicmfs_ops;
+static const struct inode_operations basicmfs_dir_inode_operations;
+
+static struct basicmfs_sb_info *BMFS_SB(struct super_block *sb)
+{
+ return sb->s_fs_info;
+}
+
+static struct basicmfs_inode_info *BMFS_I(struct inode *inode)
+{
+ return inode->i_private;
+}
+
+/*
+ * Allocate a base page and assign it to the inode at the given page offset
+ * Takes the sbi->lock.
+ * Returns the allocated page if there is one, else NULL
+ */
+static struct page *basicmfs_alloc_page(struct basicmfs_inode_info *inode_info,
+ struct basicmfs_sb_info *sbi, u64 page_offset)
+{
+ u8 *kaddr;
+ u64 pages_added;
+ u64 alloc_size = 64;
+ struct page *page = NULL;
+
+ spin_lock(&sbi->lock);
+
+ /* First, do we have any free pages available? */
+ if (sbi->free_pages == 0) {
+ /* Try to allocate more pages if we can */
+ alloc_size = min(alloc_size, sbi->max_pages - sbi->num_pages);
+ if (alloc_size == 0)
+ goto unlock;
+
+ pages_added = alloc_pages_bulk_list(GFP_HIGHUSER, alloc_size, &sbi->free_list);
+
+ if (pages_added == 0)
+ goto unlock;
+
+ sbi->num_pages += pages_added;
+ sbi->free_pages += pages_added;
+ }
+
+ page = list_first_entry(&sbi->free_list, struct page, lru);
+ list_del(&page->lru);
+ sbi->free_pages--;
+
+ /* Zero the page outside of the critical section */
+ spin_unlock(&sbi->lock);
+
+ kaddr = kmap_local_page(page);
+ memset(kaddr, 0, PAGE_SIZE);
+ kunmap_local(kaddr);
+
+ spin_lock(&sbi->lock);
+
+ list_add(&page->lru, &sbi->active_list);
+
+unlock:
+ spin_unlock(&sbi->lock);
+ return page;
+}
+
+static void basicmfs_return_page(struct page *page, struct basicmfs_sb_info *sbi)
+{
+ spin_lock(&sbi->lock);
+
+ list_del(&page->lru);
+ /*
+ * We don't need to put page here for being unmapped that seems to have
+ * been handled by the unmapping code.
+ */
+
+ list_add_tail(&page->lru, &sbi->free_list);
+ sbi->free_pages++;
+
+ spin_unlock(&sbi->lock);
+}
+
+static void basicmfs_free_range(struct inode *inode, u64 offset, loff_t len)
+{
+ struct basicmfs_sb_info *sbi = BMFS_SB(inode->i_sb);
+ struct basicmfs_inode_info *inode_info = BMFS_I(inode);
+ struct address_space *mapping = inode_info->mapping;
+ struct folio_batch fbatch;
+ int i;
+ pgoff_t cur_offset = offset >> PAGE_SHIFT;
+ pgoff_t end_offset = (offset + len) >> PAGE_SHIFT;
+
+ folio_batch_init(&fbatch);
+ while (cur_offset < end_offset) {
+ filemap_get_folios(mapping, &cur_offset, end_offset - 1, &fbatch);
+
+ for (i = 0; i < fbatch.nr; i++) {
+ folio_lock(fbatch.folios[i]);
+ filemap_remove_folio(fbatch.folios[i]);
+ folio_unlock(fbatch.folios[i]);
+ basicmfs_return_page(folio_page(fbatch.folios[i], 0), sbi);
+ }
+
+ folio_batch_release(&fbatch);
+ }
+}
+
+static vm_fault_t basicmfs_fault(struct vm_fault *vmf)
+{
+ struct vm_area_struct *vma = vmf->vma;
+ struct address_space *mapping = vma->vm_file->f_mapping;
+ struct inode *inode = vma->vm_file->f_inode;
+ struct basicmfs_inode_info *inode_info;
+ struct basicmfs_sb_info *sbi;
+ struct page *page = NULL;
+ bool new_page = true;
+ bool cow_fault = false;
+ u64 pgoff = ((vmf->address - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
+ vm_fault_t ret = 0;
+ pte_t entry;
+
+ inode_info = BMFS_I(inode);
+ sbi = BMFS_SB(inode->i_sb);
+
+ if (!vmf->pte) {
+ if (pte_alloc(vma->vm_mm, vmf->pmd))
+ return VM_FAULT_OOM;
+ }
+
+ vmf->pte = pte_offset_map(vmf->pmd, vmf->address);
+ vmf->orig_pte = *vmf->pte;
+ if (!pte_none(vmf->orig_pte) && pte_present(vmf->orig_pte)) {
+ if (!(vmf->flags & FAULT_FLAG_WRITE)) {
+ /*
+ * It looks like the PTE is already populated,
+ * so maybe two threads raced to first fault.
+ */
+ ret = VM_FAULT_NOPAGE;
+ goto unmap;
+ }
+
+ cow_fault = true;
+ }
+
+ /* Get the page if it was preallocated */
+ page = mtree_erase(&inode_info->falloc_mt, pgoff);
+
+ /* Try to allocate the page if it hasn't been already */
+ if (!page) {
+ page = basicmfs_alloc_page(inode_info, sbi, pgoff);
+ if (!page) {
+ ret = VM_FAULT_OOM;
+ goto unmap;
+ }
+ }
+
+ if (!pte_none(vmf->orig_pte) && !pte_present(vmf->orig_pte)) {
+ /* Swapped out page */
+ struct page *ret_page;
+ swp_entry_t swp_entry = pte_to_swp_entry(vmf->orig_pte);
+
+ ret_page = fbmm_read_swap_entry(vmf, swp_entry, pgoff, page);
+ if (page != ret_page) {
+ /*
+ * A physical page was already being used for this virt page
+ * or there was an error, so we can return the page we allocated.
+ */
+ basicmfs_return_page(page, sbi);
+ page = ret_page;
+ new_page = false;
+ }
+ if (!page) {
+ pr_warn("BasicMFS: Error swapping in page! %lx\n", vmf->address);
+ goto unmap;
+ }
+ }
+
+ vmf->ptl = pte_lockptr(vma->vm_mm, vmf->pmd);
+ spin_lock(vmf->ptl);
+ /* Check if some other thread faulted here */
+ if (!pte_same(vmf->orig_pte, *vmf->pte)) {
+ if (new_page)
+ basicmfs_return_page(page, sbi);
+ goto unlock;
+ }
+
+ /* Handle COW fault */
+ if (cow_fault) {
+ u8 *src_kaddr, *dst_kaddr;
+ struct page *old_page;
+ struct folio *old_folio;
+ unsigned long old_pfn;
+
+ old_pfn = pte_pfn(vmf->orig_pte);
+ old_page = pfn_to_page(old_pfn);
+
+ lock_page(old_page);
+
+ /*
+ * If there's more than one reference to this page, we need to copy it.
+ * Otherwise, we can just reuse it
+ */
+ if (page_mapcount(old_page) > 1) {
+ src_kaddr = kmap_local_page(old_page);
+ dst_kaddr = kmap_local_page(page);
+ memcpy(dst_kaddr, src_kaddr, PAGE_SIZE);
+ kunmap_local(dst_kaddr);
+ kunmap_local(src_kaddr);
+ } else {
+ basicmfs_return_page(page, sbi);
+ page = old_page;
+ }
+ /*
+ * Drop a reference to old_page even if we are going to keep it
+ * because the reference will be increased at the end of the fault
+ */
+ put_page(old_page);
+ /* Decrease the filepage and rmap count for the same reason */
+ percpu_counter_dec(&vma->vm_mm->rss_stat[MM_FILEPAGES]);
+ folio_remove_rmap_pte(page_folio(old_page), old_page, vma);
+
+ old_folio = page_folio(old_page);
+ /*
+ * If we are copying a page for the process that originally faulted the
+ * page, we have to replace the mapping.
+ */
+ if (mapping == old_folio->mapping) {
+ if (old_page != page)
+ replace_page_cache_folio(old_folio, page_folio(page));
+ new_page = false;
+ }
+ unlock_page(old_page);
+ }
+
+ if (new_page)
+ /*
+ * We want to manage the folio ourselves, and don't want it on the LRU lists,
+ * so we use __filemap_add_folio instead of filemap_add_folio.
+ */
+ __filemap_add_folio(mapping, page_folio(page), pgoff, GFP_KERNEL, NULL);
+
+ /* Construct the pte entry */
+ entry = mk_pte(page, vma->vm_page_prot);
+ entry = pte_mkyoung(entry);
+ if (vma->vm_flags & VM_WRITE)
+ entry = pte_mkwrite_novma(pte_mkdirty(entry));
+
+ folio_add_file_rmap_pte(page_folio(page), page, vma);
+ percpu_counter_inc(&vma->vm_mm->rss_stat[MM_FILEPAGES]);
+ set_pte_at(vma->vm_mm, vmf->address, vmf->pte, entry);
+
+ update_mmu_cache(vma, vmf->address, vmf->pte);
+ vmf->page = page;
+ get_page(page);
+ flush_tlb_page(vma, vmf->address);
+ ret = VM_FAULT_NOPAGE;
+
+unlock:
+ spin_unlock(vmf->ptl);
+unmap:
+ pte_unmap(vmf->pte);
+ return ret;
+}
+
+const struct vm_operations_struct basicmfs_vm_ops = {
+ .fault = basicmfs_fault,
+ .page_mkwrite = basicmfs_fault,
+ .pfn_mkwrite = basicmfs_fault,
+};
+
+static int basicmfs_mmap(struct file *file, struct vm_area_struct *vma)
+{
+ struct inode *inode = file_inode(file);
+ struct basicmfs_inode_info *inode_info = BMFS_I(inode);
+
+ file_accessed(file);
+ vma->vm_ops = &basicmfs_vm_ops;
+
+ inode_info->file_va_start = vma->vm_start - (vma->vm_pgoff << PAGE_SHIFT);
+ inode_info->mapping = file->f_mapping;
+
+ return 0;
+}
+
+static int basicmfs_release(struct inode *inode, struct file *file)
+{
+ struct basicmfs_sb_info *sbi = BMFS_SB(inode->i_sb);
+ struct basicmfs_inode_info *inode_info = BMFS_I(inode);
+ struct page *page;
+ unsigned long index = 0;
+ unsigned long free_count = 0;
+
+ basicmfs_free_range(inode, 0, inode->i_size);
+
+ mt_for_each(&inode_info->falloc_mt, page, index, ULONG_MAX) {
+ basicmfs_return_page(page, sbi);
+ free_count++;
+ }
+
+ mtree_destroy(&inode_info->falloc_mt);
+ kfree(inode_info);
+
+ return 0;
+}
+
+static long basicmfs_fallocate(struct file *file, int mode, loff_t offset, loff_t len)
+{
+ struct inode *inode = file_inode(file);
+ struct basicmfs_sb_info *sbi = BMFS_SB(inode->i_sb);
+ struct basicmfs_inode_info *inode_info = BMFS_I(inode);
+ struct page *page;
+ loff_t off;
+
+ if (mode & FALLOC_FL_PUNCH_HOLE) {
+ basicmfs_free_range(inode, offset, len);
+ return 0;
+ } else if (mode != 0) {
+ return -EOPNOTSUPP;
+ }
+
+ for (off = offset; off < offset + len; off += PAGE_SIZE) {
+ page = basicmfs_alloc_page(inode_info, sbi, off >> PAGE_SHIFT);
+ mtree_store(&inode_info->falloc_mt, off >> PAGE_SHIFT, page, GFP_KERNEL);
+ if (!page)
+ return -ENOMEM;
+ }
+
+ return 0;
+}
+
+const struct file_operations basicmfs_file_operations = {
+ .mmap = basicmfs_mmap,
+ .release = basicmfs_release,
+ .fsync = noop_fsync,
+ .llseek = generic_file_llseek,
+ .get_unmapped_area = generic_get_unmapped_area_topdown,
+ .fallocate = basicmfs_fallocate,
+};
+
+const struct inode_operations basicmfs_file_inode_operations = {
+ .setattr = simple_setattr,
+ .getattr = simple_getattr,
+};
+
+const struct address_space_operations basicmfs_aops = {
+ .direct_IO = noop_direct_IO,
+ .dirty_folio = noop_dirty_folio,
+ .writepage = fbmm_writepage,
+};
+
+static struct inode *basicmfs_get_inode(struct super_block *sb,
+ const struct inode *dir, umode_t mode, dev_t dev)
+{
+ struct inode *inode = new_inode(sb);
+ struct basicmfs_inode_info *info;
+
+ if (!inode)
+ return NULL;
+
+ info = kzalloc(sizeof(struct basicmfs_inode_info), GFP_KERNEL);
+ if (!info)
+ return NULL;
+ mt_init(&info->falloc_mt);
+ info->file_va_start = 0;
+
+ inode->i_ino = get_next_ino();
+ inode_init_owner(&nop_mnt_idmap, inode, dir, mode);
+ inode->i_mapping->a_ops = &basicmfs_aops;
+ inode->i_flags |= S_DAX;
+ inode->i_private = info;
+ switch (mode & S_IFMT) {
+ case S_IFREG:
+ inode->i_op = &basicmfs_file_inode_operations;
+ inode->i_fop = &basicmfs_file_operations;
+ break;
+ case S_IFDIR:
+ inode->i_op = &basicmfs_dir_inode_operations;
+ inode->i_fop = &simple_dir_operations;
+
+ /* Directory inodes start off with i_nlink == 2 (for "." entry) */
+ inc_nlink(inode);
+ break;
+ default:
+ return NULL;
+ }
+
+ return inode;
+}
+
+static int basicmfs_mknod(struct mnt_idmap *idmap, struct inode *dir,
+ struct dentry *dentry, umode_t mode, dev_t dev)
+{
+ struct inode *inode = basicmfs_get_inode(dir->i_sb, dir, mode, dev);
+ int error = -ENOSPC;
+
+ if (inode) {
+ d_instantiate(dentry, inode);
+ dget(dentry); /* Extra count - pin the dentry in core */
+ error = 0;
+ }
+
+ return error;
+}
+
+static int basicmfs_mkdir(struct mnt_idmap *idmap, struct inode *dir,
+ struct dentry *dentry, umode_t mode)
+{
+ return -EINVAL;
+}
+
+static int basicmfs_create(struct mnt_idmap *idmap, struct inode *dir,
+ struct dentry *dentry, umode_t mode, bool excl)
+{
+ // TODO: Replace 0777 with mode and see if anything breaks
+ return basicmfs_mknod(idmap, dir, dentry, 0777 | S_IFREG, 0);
+}
+
+static int basicmfs_symlink(struct mnt_idmap *idmap, struct inode *dir,
+ struct dentry *dentry, const char *symname)
+{
+ return -EINVAL;
+}
+
+static int basicmfs_tmpfile(struct mnt_idmap *idmap,
+ struct inode *dir, struct file *file, umode_t mode)
+{
+ struct inode *inode;
+
+ inode = basicmfs_get_inode(dir->i_sb, dir, mode, 0);
+ if (!inode)
+ return -ENOSPC;
+ d_tmpfile(file, inode);
+ return finish_open_simple(file, 0);
+}
+
+static const struct inode_operations basicmfs_dir_inode_operations = {
+ .create = basicmfs_create,
+ .lookup = simple_lookup,
+ .link = simple_link,
+ .unlink = simple_unlink,
+ .symlink = basicmfs_symlink,
+ .mkdir = basicmfs_mkdir,
+ .rmdir = simple_rmdir,
+ .mknod = basicmfs_mknod,
+ .rename = simple_rename,
+ .tmpfile = basicmfs_tmpfile,
+};
+
+static int basicmfs_statfs(struct dentry *dentry, struct kstatfs *buf)
+{
+ struct super_block *sb = dentry->d_sb;
+ struct basicmfs_sb_info *sbi = BMFS_SB(sb);
+
+ buf->f_type = sb->s_magic;
+ buf->f_bsize = PAGE_SIZE;
+ buf->f_blocks = sbi->num_pages;
+ buf->f_bfree = buf->f_bavail = sbi->free_pages;
+ buf->f_files = LONG_MAX;
+ buf->f_ffree = LONG_MAX;
+ buf->f_namelen = 255;
+
+ return 0;
+}
+
+static int basicmfs_show_options(struct seq_file *m, struct dentry *root)
+{
+ return 0;
+}
+
+#define BASICMFS_MAX_PAGEOUT 512
+static long basicmfs_nr_cached_objects(struct super_block *sb, struct shrink_control *sc)
+{
+ struct basicmfs_sb_info *sbi = BMFS_SB(sb);
+ long nr = 0;
+
+ spin_lock(&sbi->lock);
+ if (sbi->free_pages > 0)
+ nr = sbi->free_pages;
+ else
+ nr = max(sbi->num_pages - sbi->free_pages, (u64)BASICMFS_MAX_PAGEOUT);
+ spin_unlock(&sbi->lock);
+
+ return nr;
+}
+
+static long basicmfs_free_cached_objects(struct super_block *sb, struct shrink_control *sc)
+{
+ LIST_HEAD(folio_list);
+ LIST_HEAD(fail_list);
+ struct basicmfs_sb_info *sbi = BMFS_SB(sb);
+ struct page *page;
+ u64 i, num_scanned;
+
+ if (sbi->free_pages > 0) {
+ spin_lock(&sbi->lock);
+ for (i = 0; i < sc->nr_to_scan && i < sbi->free_pages; i++) {
+ page = list_first_entry(&sbi->free_list, struct page, lru);
+ list_del(&page->lru);
+ put_page(page);
+ }
+
+ sbi->num_pages -= i;
+ sbi->free_pages -= i;
+ spin_unlock(&sbi->lock);
+ } else if (sbi->num_pages > 0) {
+ spin_lock(&sbi->lock);
+ for (i = 0; i < sc->nr_to_scan && sbi->num_pages > 0; i++) {
+ page = list_first_entry(&sbi->active_list, struct page, lru);
+ list_move(&page->lru, &folio_list);
+ sbi->num_pages--;
+ }
+ spin_unlock(&sbi->lock);
+
+ num_scanned = i;
+ for (i = 0; i < num_scanned && !list_empty(&folio_list); i++) {
+ page = list_first_entry(&folio_list, struct page, lru);
+ list_del(&page->lru);
+ if (fbmm_swapout_folio(page_folio(page)))
+ list_add_tail(&page->lru, &fail_list);
+ else
+ put_page(page);
+ }
+
+ spin_lock(&sbi->lock);
+ while (!list_empty(&fail_list)) {
+ page = list_first_entry(&fail_list, struct page, lru);
+ list_del(&page->lru);
+ list_add_tail(&page->lru, &sbi->active_list);
+ sbi->num_pages++;
+ }
+ spin_unlock(&sbi->lock);
+
+ }
+
+ sc->nr_scanned = i;
+ return i;
+}
+
+static const struct super_operations basicmfs_ops = {
+ .statfs = basicmfs_statfs,
+ .drop_inode = generic_delete_inode,
+ .show_options = basicmfs_show_options,
+ .nr_cached_objects = basicmfs_nr_cached_objects,
+ .free_cached_objects = basicmfs_free_cached_objects,
+ .copy_page_range = fbmm_copy_page_range,
+};
+
+static int basicmfs_fill_super(struct super_block *sb, struct fs_context *fc)
+{
+ struct inode *inode;
+ struct basicmfs_sb_info *sbi = kzalloc(sizeof(struct basicmfs_sb_info), GFP_KERNEL);
+ u64 nr_pages = *(u64 *)fc->fs_private;
+ u64 alloc_size = 1024;
+
+ if (!sbi)
+ return -ENOMEM;
+
+ sb->s_fs_info = sbi;
+ sb->s_maxbytes = MAX_LFS_FILESIZE;
+ sb->s_magic = 0xDEADBEEF;
+ sb->s_op = &basicmfs_ops;
+ sb->s_time_gran = 1;
+ sb->s_blocksize = PAGE_SIZE;
+ sb->s_blocksize_bits = PAGE_SHIFT;
+
+ spin_lock_init(&sbi->lock);
+ INIT_LIST_HEAD(&sbi->free_list);
+ INIT_LIST_HEAD(&sbi->active_list);
+ sbi->max_pages = nr_pages;
+ sbi->num_pages = 0;
+ for (int i = 0; i < nr_pages / alloc_size; i++)
+ sbi->num_pages += alloc_pages_bulk_list(GFP_HIGHUSER, alloc_size, &sbi->free_list);
+ sbi->free_pages = sbi->num_pages;
+
+ inode = basicmfs_get_inode(sb, NULL, S_IFDIR | 0755, 0);
+ sb->s_root = d_make_root(inode);
+ if (!sb->s_root) {
+ kfree(sbi);
+ return -ENOMEM;
+ }
+
+ return 0;
+}
+
+static int basicmfs_get_tree(struct fs_context *fc)
+{
+ return get_tree_nodev(fc, basicmfs_fill_super);
+}
+
+enum basicmfs_param {
+ Opt_numpages,
+};
+
+const struct fs_parameter_spec basicmfs_fs_parameters[] = {
+ fsparam_u64("numpages", Opt_numpages),
+ {},
+};
+
+static int basicmfs_parse_param(struct fs_context *fc, struct fs_parameter *param)
+{
+ struct fs_parse_result result;
+ u64 *num_pages = (u64 *)fc->fs_private;
+ int opt;
+
+ opt = fs_parse(fc, basicmfs_fs_parameters, param, &result);
+ if (opt < 0) {
+ /*
+ * We might like to report bad mount options here;
+ * but traditionally ramfs has ignored all mount options,
+ * and as it is used as a !CONFIG_SHMEM simple substitute
+ * for tmpfs, better continue to ignore other mount options.
+ */
+ if (opt == -ENOPARAM)
+ opt = 0;
+ return opt;
+ }
+
+ switch (opt) {
+ case Opt_numpages:
+ *num_pages = result.uint_64;
+ break;
+ };
+
+ return 0;
+}
+
+static void basicmfs_free_fc(struct fs_context *fc)
+{
+ kfree(fc->fs_private);
+}
+
+static const struct fs_context_operations basicmfs_context_ops = {
+ .free = basicmfs_free_fc,
+ .parse_param = basicmfs_parse_param,
+ .get_tree = basicmfs_get_tree,
+};
+
+static int basicmfs_init_fs_context(struct fs_context *fc)
+{
+ fc->ops = &basicmfs_context_ops;
+
+ fc->fs_private = kzalloc(sizeof(u64), GFP_KERNEL);
+ /* Set a default number of pages to use */
+ *(u64 *)fc->fs_private = 128 * 1024;
+ return 0;
+}
+
+static void basicmfs_kill_sb(struct super_block *sb)
+{
+ struct basicmfs_sb_info *sbi = BMFS_SB(sb);
+ struct page *page, *tmp;
+
+ spin_lock(&sbi->lock);
+
+ /*
+ * Return the pages we took to the kernel.
+ * All the pages should be in the free list at this point
+ */
+ list_for_each_entry_safe(page, tmp, &sbi->free_list, lru) {
+ list_del(&page->lru);
+ put_page(page);
+ }
+
+ spin_unlock(&sbi->lock);
+
+ kfree(sbi);
+
+ kill_litter_super(sb);
+}
+
+static struct file_system_type basicmfs_fs_type = {
+ .owner = THIS_MODULE,
+ .name = "BasicMFS",
+ .init_fs_context = basicmfs_init_fs_context,
+ .parameters = basicmfs_fs_parameters,
+ .kill_sb = basicmfs_kill_sb,
+ .fs_flags = FS_USERNS_MOUNT,
+};
+
+static int __init init_basicmfs(void)
+{
+ printk(KERN_INFO "Starting BasicMFS");
+ register_filesystem(&basicmfs_fs_type);
+
+ return 0;
+}
+module_init(init_basicmfs);
+
+static void cleanup_basicmfs(void)
+{
+ printk(KERN_INFO "Removing BasicMFS");
+ unregister_filesystem(&basicmfs_fs_type);
+}
+module_exit(cleanup_basicmfs);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Bijan Tabatabai");
diff --git a/BasicMFS/basic.h b/BasicMFS/basic.h
new file mode 100644
index 000000000000..8e727201aca3
--- /dev/null
+++ b/BasicMFS/basic.h
@@ -0,0 +1,29 @@
+#ifndef BASIC_MMFS_H
+#define BASIC_MMFS_H
+
+#include <linux/types.h>
+#include <linux/fs.h>
+#include <linux/maple_tree.h>
+#include <linux/spinlock.h>
+#include <linux/sched.h>
+
+struct basicmfs_sb_info {
+ spinlock_t lock;
+ struct list_head free_list;
+ struct list_head active_list;
+ u64 num_pages;
+ u64 max_pages;
+ u64 free_pages;
+};
+
+struct basicmfs_inode_info {
+ // Maple tree mapping the page offset to the folio mapped to that offset
+ // Used to hold preallocated pages that haven't been mapped yet
+ struct maple_tree falloc_mt;
+ // The first virtual address this file is associated with.
+ u64 file_va_start;
+ // The file offset to folio mapping from the file
+ struct address_space *mapping;
+};
+
+#endif //BASIC_MMFS_H
--
2.34.1
