fs: replace mmap hook with .mmap_prepare for simple mappings

Since commit c84bf6d ("mm: introduce new .mmap_prepare() file
callback"), the f_op->mmap() hook has been deprecated in favour of
f_op->mmap_prepare().

This callback is invoked in the mmap() logic far earlier, so error handling
can be performed more safely without complicated and bug-prone state
unwinding required should an error arise.

This hook also avoids passing a pointer to a not-yet-correctly-established
VMA avoiding any issues with referencing this data structure.

It rather provides a pointer to the new struct vm_area_desc descriptor type
which contains all required state and allows easy setting of required
parameters without any consideration needing to be paid to locking or
reference counts.

Note that nested filesystems like overlayfs are compatible with an
.mmap_prepare() callback since commit bb666b7 ("mm: add mmap_prepare()
compatibility layer for nested file systems").

In this patch we apply this change to file systems with relatively simple
mmap() hook logic - exfat, ceph, f2fs, bcachefs, zonefs, btrfs, ocfs2,
orangefs, nilfs2, romfs, ramfs and aio.

Signed-off-by: Lorenzo Stoakes <[email protected]>
Link: https://lore.kernel.org/f528ac4f35b9378931bd800920fee53fc0c5c74d.1750099179.git.lorenzo.stoakes@oracle.com
Acked-by: Damien Le Moal <[email protected]>
Reviewed-by: Jan Kara <[email protected]>
Reviewed-by: Viacheslav Dubeyko <[email protected]>
Signed-off-by: Christian Brauner <[email protected]>

Author: lorenzo-stoakes

fs/aio.c

@@ -392,15 +392,15 @@ static const struct vm_operations_struct aio_ring_vm_ops = {
 #endif
 };
 
-static int aio_ring_mmap(struct file *file, struct vm_area_struct *vma)
+static int aio_ring_mmap_prepare(struct vm_area_desc *desc)
 {
-	vm_flags_set(vma, VM_DONTEXPAND);
-	vma->vm_ops = &aio_ring_vm_ops;
+	desc->vm_flags |= VM_DONTEXPAND;
+	desc->vm_ops = &aio_ring_vm_ops;
 	return 0;
 }
 
 static const struct file_operations aio_ring_fops = {
-	.mmap = aio_ring_mmap,
+	.mmap_prepare = aio_ring_mmap_prepare,
 };
 
 #if IS_ENABLED(CONFIG_MIGRATION)

fs/bcachefs/fs.c

@@ -1553,11 +1553,11 @@ static const struct vm_operations_struct bch_vm_ops = {
 	.page_mkwrite   = bch2_page_mkwrite,
 };
 
-static int bch2_mmap(struct file *file, struct vm_area_struct *vma)
+static int bch2_mmap_prepare(struct vm_area_desc *desc)
 {
-	file_accessed(file);
+	file_accessed(desc->file);
 
-	vma->vm_ops = &bch_vm_ops;
+	desc->vm_ops = &bch_vm_ops;
 	return 0;
 }
 
@@ -1740,7 +1740,7 @@ static const struct file_operations bch_file_operations = {
 	.llseek		= bch2_llseek,
 	.read_iter	= bch2_read_iter,
 	.write_iter	= bch2_write_iter,
-	.mmap		= bch2_mmap,
+	.mmap_prepare	= bch2_mmap_prepare,
 	.get_unmapped_area = thp_get_unmapped_area,
 	.fsync		= bch2_fsync,
 	.splice_read	= filemap_splice_read,

fs/btrfs/file.c

@@ -1978,15 +1978,16 @@ static const struct vm_operations_struct btrfs_file_vm_ops = {
 	.page_mkwrite	= btrfs_page_mkwrite,
 };
 
-static int btrfs_file_mmap(struct file	*filp, struct vm_area_struct *vma)
+static int btrfs_file_mmap_prepare(struct vm_area_desc *desc)
 {
+	struct file *filp = desc->file;
 	struct address_space *mapping = filp->f_mapping;
 
 	if (!mapping->a_ops->read_folio)
 		return -ENOEXEC;
 
 	file_accessed(filp);
-	vma->vm_ops = &btrfs_file_vm_ops;
+	desc->vm_ops = &btrfs_file_vm_ops;
 
 	return 0;
 }
@@ -3765,7 +3766,7 @@ const struct file_operations btrfs_file_operations = {
 	.splice_read	= filemap_splice_read,
 	.write_iter	= btrfs_file_write_iter,
 	.splice_write	= iter_file_splice_write,
-	.mmap		= btrfs_file_mmap,
+	.mmap_prepare	= btrfs_file_mmap_prepare,
 	.open		= btrfs_file_open,
 	.release	= btrfs_release_file,
 	.get_unmapped_area = thp_get_unmapped_area,

fs/ceph/addr.c

@@ -2330,13 +2330,13 @@ static const struct vm_operations_struct ceph_vmops = {
 	.page_mkwrite	= ceph_page_mkwrite,
 };
 
-int ceph_mmap(struct file *file, struct vm_area_struct *vma)
+int ceph_mmap_prepare(struct vm_area_desc *desc)
 {
-	struct address_space *mapping = file->f_mapping;
+	struct address_space *mapping = desc->file->f_mapping;
 
 	if (!mapping->a_ops->read_folio)
 		return -ENOEXEC;
-	vma->vm_ops = &ceph_vmops;
+	desc->vm_ops = &ceph_vmops;
 	return 0;
 }
 

fs/ceph/file.c

@@ -3171,7 +3171,7 @@ const struct file_operations ceph_file_fops = {
 	.llseek = ceph_llseek,
 	.read_iter = ceph_read_iter,
 	.write_iter = ceph_write_iter,
-	.mmap = ceph_mmap,
+	.mmap_prepare = ceph_mmap_prepare,
 	.fsync = ceph_fsync,
 	.lock = ceph_lock,
 	.setlease = simple_nosetlease,

fs/ceph/super.h

@@ -1286,7 +1286,7 @@ extern void __ceph_touch_fmode(struct ceph_inode_info *ci,
 /* addr.c */
 extern const struct address_space_operations ceph_aops;
 extern const struct netfs_request_ops ceph_netfs_ops;
-extern int ceph_mmap(struct file *file, struct vm_area_struct *vma);
+int ceph_mmap_prepare(struct vm_area_desc *desc);
 extern int ceph_uninline_data(struct file *file);
 extern int ceph_pool_perm_check(struct inode *inode, int need);
 extern void ceph_pool_perm_destroy(struct ceph_mds_client* mdsc);

fs/exfat/file.c

@@ -683,13 +683,15 @@ static const struct vm_operations_struct exfat_file_vm_ops = {
 	.page_mkwrite	= exfat_page_mkwrite,
 };
 
-static int exfat_file_mmap(struct file *file, struct vm_area_struct *vma)
+static int exfat_file_mmap_prepare(struct vm_area_desc *desc)
 {
-	if (unlikely(exfat_forced_shutdown(file_inode(file)->i_sb)))
+	struct file *file = desc->file;
+
+	if (unlikely(exfat_forced_shutdown(file_inode(desc->file)->i_sb)))
 		return -EIO;
 
 	file_accessed(file);
-	vma->vm_ops = &exfat_file_vm_ops;
+	desc->vm_ops = &exfat_file_vm_ops;
 	return 0;
 }
 
@@ -710,7 +712,7 @@ const struct file_operations exfat_file_operations = {
 #ifdef CONFIG_COMPAT
 	.compat_ioctl = exfat_compat_ioctl,
 #endif
-	.mmap		= exfat_file_mmap,
+	.mmap_prepare	= exfat_file_mmap_prepare,
 	.fsync		= exfat_file_fsync,
 	.splice_read	= exfat_splice_read,
 	.splice_write	= iter_file_splice_write,

fs/f2fs/file.c

@@ -532,8 +532,9 @@ static loff_t f2fs_llseek(struct file *file, loff_t offset, int whence)
 	return -EINVAL;
 }
 
-static int f2fs_file_mmap(struct file *file, struct vm_area_struct *vma)
+static int f2fs_file_mmap_prepare(struct vm_area_desc *desc)
 {
+	struct file *file = desc->file;
 	struct inode *inode = file_inode(file);
 
 	if (unlikely(f2fs_cp_error(F2FS_I_SB(inode))))
@@ -543,7 +544,7 @@ static int f2fs_file_mmap(struct file *file, struct vm_area_struct *vma)
 		return -EOPNOTSUPP;
 
 	file_accessed(file);
-	vma->vm_ops = &f2fs_file_vm_ops;
+	desc->vm_ops = &f2fs_file_vm_ops;
 
 	f2fs_down_read(&F2FS_I(inode)->i_sem);
 	set_inode_flag(inode, FI_MMAP_FILE);
@@ -5376,7 +5377,7 @@ const struct file_operations f2fs_file_operations = {
 	.iopoll		= iocb_bio_iopoll,
 	.open		= f2fs_file_open,
 	.release	= f2fs_release_file,
-	.mmap		= f2fs_file_mmap,
+	.mmap_prepare	= f2fs_file_mmap_prepare,
 	.flush		= f2fs_file_flush,
 	.fsync		= f2fs_sync_file,
 	.fallocate	= f2fs_fallocate,

fs/nilfs2/file.c

@@ -125,10 +125,10 @@ static const struct vm_operations_struct nilfs_file_vm_ops = {
 	.page_mkwrite	= nilfs_page_mkwrite,
 };
 
-static int nilfs_file_mmap(struct file *file, struct vm_area_struct *vma)
+static int nilfs_file_mmap_prepare(struct vm_area_desc *desc)
 {
-	file_accessed(file);
-	vma->vm_ops = &nilfs_file_vm_ops;
+	file_accessed(desc->file);
+	desc->vm_ops = &nilfs_file_vm_ops;
 	return 0;
 }
 
@@ -144,7 +144,7 @@ const struct file_operations nilfs_file_operations = {
 #ifdef CONFIG_COMPAT
 	.compat_ioctl	= nilfs_compat_ioctl,
 #endif	/* CONFIG_COMPAT */
-	.mmap		= nilfs_file_mmap,
+	.mmap_prepare	= nilfs_file_mmap_prepare,
 	.open		= generic_file_open,
 	/* .release	= nilfs_release_file, */
 	.fsync		= nilfs_sync_file,

fs/ocfs2/file.c

@@ -2800,7 +2800,7 @@ const struct inode_operations ocfs2_special_file_iops = {
  */
 const struct file_operations ocfs2_fops = {
 	.llseek		= ocfs2_file_llseek,
-	.mmap		= ocfs2_mmap,
+	.mmap_prepare	= ocfs2_mmap_prepare,
 	.fsync		= ocfs2_sync_file,
 	.release	= ocfs2_file_release,
 	.open		= ocfs2_file_open,
@@ -2850,7 +2850,7 @@ const struct file_operations ocfs2_dops = {
  */
 const struct file_operations ocfs2_fops_no_plocks = {
 	.llseek		= ocfs2_file_llseek,
-	.mmap		= ocfs2_mmap,
+	.mmap_prepare	= ocfs2_mmap_prepare,
 	.fsync		= ocfs2_sync_file,
 	.release	= ocfs2_file_release,
 	.open		= ocfs2_file_open,