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exfat: reduce unnecessary writes during mmap write

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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: Yuling Dong <yuling-dong@qq.com>
Reviewed-by: Yuezhang Mo <Yuezhang.Mo@sony.com>
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
This commit is contained in:
Yuling Dong
2026-01-15 13:05:23 +08:00
committed by Namjae Jeon
parent 8ffe56b104
commit 0914882bdd
1 changed files with 6 additions and 9 deletions
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15
fs/exfat/file.c
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@@ -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);