Add the ability to set up a shared anonymous mapping based on a VMA descriptor rather than a VMA.
This is a prerequisite for converting to the char mm driver to use the mmap_prepare hook. Signed-off-by: Lorenzo Stoakes <[email protected]> --- include/linux/shmem_fs.h | 3 ++- mm/shmem.c | 41 ++++++++++++++++++++++++++++++++-------- 2 files changed, 35 insertions(+), 9 deletions(-) diff --git a/include/linux/shmem_fs.h b/include/linux/shmem_fs.h index 0e47465ef0fd..5b368f9549d6 100644 --- a/include/linux/shmem_fs.h +++ b/include/linux/shmem_fs.h @@ -94,7 +94,8 @@ extern struct file *shmem_kernel_file_setup(const char *name, loff_t size, unsigned long flags); extern struct file *shmem_file_setup_with_mnt(struct vfsmount *mnt, const char *name, loff_t size, unsigned long flags); -extern int shmem_zero_setup(struct vm_area_struct *); +int shmem_zero_setup(struct vm_area_struct *vma); +int shmem_zero_setup_desc(struct vm_area_desc *desc); extern unsigned long shmem_get_unmapped_area(struct file *, unsigned long addr, unsigned long len, unsigned long pgoff, unsigned long flags); extern int shmem_lock(struct file *file, int lock, struct ucounts *ucounts); diff --git a/mm/shmem.c b/mm/shmem.c index df02a2e0ebbb..72aa176023de 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -5893,14 +5893,9 @@ struct file *shmem_file_setup_with_mnt(struct vfsmount *mnt, const char *name, } EXPORT_SYMBOL_GPL(shmem_file_setup_with_mnt); -/** - * shmem_zero_setup - setup a shared anonymous mapping - * @vma: the vma to be mmapped is prepared by do_mmap - */ -int shmem_zero_setup(struct vm_area_struct *vma) +static struct file *__shmem_zero_setup(unsigned long start, unsigned long end, vm_flags_t vm_flags) { - struct file *file; - loff_t size = vma->vm_end - vma->vm_start; + loff_t size = end - start; /* * Cloning a new file under mmap_lock leads to a lock ordering conflict @@ -5908,7 +5903,18 @@ int shmem_zero_setup(struct vm_area_struct *vma) * accessible to the user through its mapping, use S_PRIVATE flag to * bypass file security, in the same way as shmem_kernel_file_setup(). */ - file = shmem_kernel_file_setup("dev/zero", size, vma->vm_flags); + return shmem_kernel_file_setup("dev/zero", size, vm_flags); +} + +/** + * shmem_zero_setup - setup a shared anonymous mapping + * @vma: the vma to be mmapped is prepared by do_mmap + * Returns: 0 on success, or error + */ +int shmem_zero_setup(struct vm_area_struct *vma) +{ + struct file *file = __shmem_zero_setup(vma->vm_start, vma->vm_end, vma->vm_flags); + if (IS_ERR(file)) return PTR_ERR(file); @@ -5920,6 +5926,25 @@ int shmem_zero_setup(struct vm_area_struct *vma) return 0; } +/** + * shmem_zero_setup_desc - same as shmem_zero_setup, but determined by VMA + * descriptor for convenience. + * @desc: Describes VMA + * Returns: 0 on success, or error + */ +int shmem_zero_setup_desc(struct vm_area_desc *desc) +{ + struct file *file = __shmem_zero_setup(desc->start, desc->end, desc->vm_flags); + + if (IS_ERR(file)) + return PTR_ERR(file); + + desc->vm_file = file; + desc->vm_ops = &shmem_anon_vm_ops; + + return 0; +} + /** * shmem_read_folio_gfp - read into page cache, using specified page allocation flags. * @mapping: the folio's address_space -- 2.51.0
