From: Lorenzo Stoakes Date: Mon, 16 Jun 2025 19:33:24 +0000 (+0100) Subject: fs/ext4: transition from deprecated .mmap hook to .mmap_prepare X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=8c90ae8fe5e34a27c500abdff76111c24c321871;p=thirdparty%2Fkernel%2Fstable.git fs/ext4: transition from deprecated .mmap hook to .mmap_prepare Since commit c84bf6dd2b83 ("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 bb666b7c2707 ("mm: add mmap_prepare() compatibility layer for nested file systems"). Signed-off-by: Lorenzo Stoakes Link: https://lore.kernel.org/5abfe526032a6698fd1bcd074a74165cda7ea57c.1750099179.git.lorenzo.stoakes@oracle.com Reviewed-by: Jan Kara Signed-off-by: Christian Brauner --- diff --git a/fs/ext4/file.c b/fs/ext4/file.c index 5b8b95936a4cf..992b4630eabca 100644 --- a/fs/ext4/file.c +++ b/fs/ext4/file.c @@ -804,9 +804,10 @@ static const struct vm_operations_struct ext4_file_vm_ops = { .page_mkwrite = ext4_page_mkwrite, }; -static int ext4_file_mmap(struct file *file, struct vm_area_struct *vma) +static int ext4_file_mmap_prepare(struct vm_area_desc *desc) { int ret; + struct file *file = desc->file; struct inode *inode = file->f_mapping->host; struct dax_device *dax_dev = EXT4_SB(inode->i_sb)->s_daxdev; @@ -821,15 +822,15 @@ static int ext4_file_mmap(struct file *file, struct vm_area_struct *vma) * We don't support synchronous mappings for non-DAX files and * for DAX files if underneath dax_device is not synchronous. */ - if (!daxdev_mapping_supported(vma->vm_flags, file_inode(vma->vm_file), dax_dev)) + if (!daxdev_mapping_supported(desc->vm_flags, file_inode(file), dax_dev)) return -EOPNOTSUPP; file_accessed(file); if (IS_DAX(file_inode(file))) { - vma->vm_ops = &ext4_dax_vm_ops; - vm_flags_set(vma, VM_HUGEPAGE); + desc->vm_ops = &ext4_dax_vm_ops; + desc->vm_flags |= VM_HUGEPAGE; } else { - vma->vm_ops = &ext4_file_vm_ops; + desc->vm_ops = &ext4_file_vm_ops; } return 0; } @@ -968,7 +969,7 @@ const struct file_operations ext4_file_operations = { #ifdef CONFIG_COMPAT .compat_ioctl = ext4_compat_ioctl, #endif - .mmap = ext4_file_mmap, + .mmap_prepare = ext4_file_mmap_prepare, .open = ext4_file_open, .release = ext4_release_file, .fsync = ext4_sync_file,