Commit 0914882b authored by Yuling Dong's avatar Yuling Dong Committed by Namjae Jeon
Browse files

exfat: reduce unnecessary writes during mmap write 



During mmap write, exfat_page_mkwrite() currently extends
valid_size to the end of the VMA range. For a large mapping,
this can push valid_size far beyond the page that actually
triggered the fault, resulting in unnecessary writes.

valid_size only needs to extend to the end of the page
being written.

Signed-off-by: default avatarYuling Dong <yuling-dong@qq.com>
Reviewed-by: default avatarYuezhang Mo <Yuezhang.Mo@sony.com>
Signed-off-by: default avatarNamjae Jeon <linkinjeon@kernel.org>
parent 8ffe56b1

fs/exfat/file.c

+6 −9
Original line number Diff line number Diff line
@@ -708,21 +708,18 @@ static ssize_t exfat_file_read_iter(struct kiocb *iocb, struct iov_iter *iter) 
static vm_fault_t exfat_page_mkwrite(struct vm_fault *vmf)

{

	int err;

	struct vm_area_struct *vma = vmf->vma;

	struct file *file = vma->vm_file;

	struct inode *inode = file_inode(file);

	struct inode *inode = file_inode(vmf->vma->vm_file);

	struct exfat_inode_info *ei = EXFAT_I(inode);

	loff_t start, end;

	loff_t new_valid_size;



	if (!inode_trylock(inode))

		return VM_FAULT_RETRY;



	start = ((loff_t)vma->vm_pgoff << PAGE_SHIFT);

	end = min_t(loff_t, i_size_read(inode),

			start + vma->vm_end - vma->vm_start);

	new_valid_size = ((loff_t)vmf->pgoff + 1) << PAGE_SHIFT;

	new_valid_size = min(new_valid_size, i_size_read(inode));



	if (ei->valid_size < end) {

		err = exfat_extend_valid_size(inode, end);

	if (ei->valid_size < new_valid_size) {

		err = exfat_extend_valid_size(inode, new_valid_size);

		if (err < 0) {

			inode_unlock(inode);

			return vmf_fs_error(err);