[RFC PATCH 15/20] famfs: Add ioctl to file_operations

John Groves
2024-02-23T17:43:01Z

This commit introduces the per-file ioctl function famfs_file_ioctl()
into struct file_operations, and introduces the famfs_file_init_dax()
function (which is called by famfs_file_ioct())

famfs_file_init_dax() associates a dax extent list with a file, making
it into a proper famfs file. It is called from the FAMFSIOC_MAP_CREATE
ioctl. Starting with an empty file (which is basically a ramfs file),
this turns the file into a DAX file backed by the specified extent list.

The other ioctls are:

FAMFSIOC_NOP - A convenient way for user space to verify it's a famfs file
FAMFSIOC_MAP_GET - Get the header of the metadata for a file
FAMFSIOC_MAP_GETEXT - Get the extents for a file

The latter two, together, are comparable to xfs_bmap. Our user space tools
use them primarly in testing.

Signed-off-by: John Groves <john@groves.net>
---
fs/famfs/famfs_file.c | 226 ++++++++++++++++++++++++++++++++++++++++++
1 file changed, 226 insertions(+)

diff --git a/fs/famfs/famfs_file.c b/fs/famfs/famfs_file.c
index 5228e9de1e3b..fd42d5966982 100644
--- a/fs/famfs/famfs_file.c
+++ b/fs/famfs/famfs_file.c
@@ -19,6 +19,231 @@
#include <uapi/linux/famfs_ioctl.h>
#include "famfs_internal.h"

+/**
+ * famfs_map_meta_alloc() - Allocate famfs file metadata
+ * @mapp: Pointer to an mcache_map_meta pointer
+ * @ext_count: The number of extents needed
+ */
+static int
+famfs_meta_alloc(
+ struct famfs_file_meta **metap,
+ size_t ext_count)
+{
+ struct famfs_file_meta *meta;
+ size_t metasz;
+
+ *metap = NULL;
+
+ metasz = sizeof(*meta) + sizeof(*(meta->tfs_extents)) * ext_count;
+
+ meta = kzalloc(metasz, GFP_KERNEL);
+ if (!meta)
+ return -ENOMEM;
+
+ meta->tfs_extent_ct = ext_count;
+ *metap = meta;
+
+ return 0;
+}
+
+static void
+famfs_meta_free(
+ struct famfs_file_meta *map)
+{
+ kfree(map);
+}
+
+/**
+ * famfs_file_init_dax() - FAMFSIOC_MAP_CREATE ioctl handler
+ * @file:
+ * @arg: ptr to struct mcioc_map in user space
+ *
+ * Setup the dax mapping for a file. Files are created empty, and then function is called
+ * (by famfs_file_ioctl()) to setup the mapping and set the file size.
+ */
+static int
+famfs_file_init_dax(
+ struct file *file,
+ void __user *arg)
+{
+ struct famfs_extent *tfs_extents = NULL;
+ struct famfs_file_meta *meta = NULL;
+ struct inode *inode;
+ struct famfs_ioc_map imap;
+ struct famfs_fs_info *fsi;
+ struct super_block *sb;
+ int alignment_errs = 0;
+ size_t extent_total = 0;
+ size_t ext_count;
+ int rc = 0;
+ int i;
+
+ rc = copy_from_user(&imap, arg, sizeof(imap));
+ if (rc)
+ return -EFAULT;
+
+ ext_count = imap.ext_list_count;
+ if (ext_count < 1) {
+ rc = -ENOSPC;
+ goto errout;
+ }
+
+ if (ext_count > FAMFS_MAX_EXTENTS) {
+ rc = -E2BIG;
+ goto errout;
+ }
+
+ inode = file_inode(file);
+ if (!inode) {
+ rc = -EBADF;
+ goto errout;
+ }
+ sb = inode->i_sb;
+ fsi = inode->i_sb->s_fs_info;
+
+ tfs_extents = &imap.ext_list[0];
+
+ rc = famfs_meta_alloc(&meta, ext_count);
+ if (rc)
+ goto errout;
+
+ meta->file_type = imap.file_type;
+ meta->file_size = imap.file_size;
+
+ /* Fill in the internal file metadata structure */
+ for (i = 0; i < imap.ext_list_count; i++) {
+ size_t len;
+ off_t offset;
+
+ offset = imap.ext_list[i].offset;
+ len = imap.ext_list[i].len;
+
+ extent_total += len;
+
+ if (WARN_ON(offset == 0 && meta->file_type != FAMFS_SUPERBLOCK)) {
+ rc = -EINVAL;
+ goto errout;
+ }
+
+ meta->tfs_extents[i].offset = offset;
+ meta->tfs_extents[i].len = len;
+
+ /* All extent addresses/offsets must be 2MiB aligned,
+ * and all but the last length must be a 2MiB multiple.
+ */
+ if (!IS_ALIGNED(offset, PMD_SIZE)) {
+ pr_err("%s: error ext %d hpa %lx not aligned\n",
+ __func__, i, offset);
+ alignment_errs++;
+ }
+ if (i < (imap.ext_list_count - 1) && !IS_ALIGNED(len, PMD_SIZE)) {
+ pr_err("%s: error ext %d length %ld not aligned\n",
+ __func__, i, len);
+ alignment_errs++;
+ }
+ }
+
+ /*
+ * File size can be <= ext list size, since extent sizes are constrained
+ * to PMD multiples
+ */
+ if (imap.file_size > extent_total) {
+ pr_err("%s: file size %lld larger than ext list size %lld\n",
+ __func__, (u64)imap.file_size, (u64)extent_total);
+ rc = -EINVAL;
+ goto errout;
+ }
+
+ if (alignment_errs > 0) {
+ pr_err("%s: there were %d alignment errors in the extent list\n",
+ __func__, alignment_errs);
+ rc = -EINVAL;
+ goto errout;
+ }
+
+ /* Publish the famfs metadata on inode->i_private */
+ inode_lock(inode);
+ if (inode->i_private) {
+ rc = -EEXIST; /* file already has famfs metadata */
+ } else {
+ inode->i_private = meta;
+ i_size_write(inode, imap.file_size);
+ inode->i_flags |= S_DAX;
+ }
+ inode_unlock(inode);
+
+ errout:
+ if (rc)
+ famfs_meta_free(meta);
+
+ return rc;
+}
+
+/**
+ * famfs_file_ioctl() - top-level famfs file ioctl handler
+ * @file:
+ * @cmd:
+ * @arg:
+ */
+static
+long
+famfs_file_ioctl(
+ struct file *file,
+ unsigned int cmd,
+ unsigned long arg)
+{
+ long rc;
+
+ switch (cmd) {
+ case FAMFSIOC_NOP:
+ rc = 0;
+ break;
+
+ case FAMFSIOC_MAP_CREATE:
+ rc = famfs_file_init_dax(file, (void *)arg);
+ break;
+
+ case FAMFSIOC_MAP_GET: {
+ struct inode *inode = file_inode(file);
+ struct famfs_file_meta *meta = inode->i_private;
+ struct famfs_ioc_map umeta;
+
+ memset(&umeta, 0, sizeof(umeta));
+
+ if (meta) {
+ /* TODO: do more to harmonize these structures */
+ umeta.extent_type = meta->tfs_extent_type;
+ umeta.file_size = i_size_read(inode);
+ umeta.ext_list_count = meta->tfs_extent_ct;
+
+ rc = copy_to_user((void __user *)arg, &umeta, sizeof(umeta));
+ if (rc)
+ pr_err("%s: copy_to_user returned %ld\n", __func__, rc);
+
+ } else {
+ rc = -EINVAL;
+ }
+ }
+ break;
+ case FAMFSIOC_MAP_GETEXT: {
+ struct inode *inode = file_inode(file);
+ struct famfs_file_meta *meta = inode->i_private;
+
+ if (meta)
+ rc = copy_to_user((void __user *)arg, meta->tfs_extents,
+ meta->tfs_extent_ct * sizeof(struct famfs_extent));
+ else
+ rc = -EINVAL;
+ }
+ break;
+ default:
+ rc = -ENOTTY;
+ break;
+ }
+
+ return rc;
+}
+
/*********************************************************************
* file_operations
*/
@@ -143,6 +368,7 @@ const struct file_operations famfs_file_operations = {
/* Custom famfs operations */
.write_iter = famfs_dax_write_iter,
.read_iter = famfs_dax_read_iter,
+ .unlocked_ioctl = famfs_file_ioctl,
.mmap = famfs_file_mmap,

/* Force PMD alignment for mmap */
--
2.43.0