On Fri, 16 Oct 2015 15:08:29 -0700 Mike Kravetz <mike.kravetz@xxxxxxxxxx> wrote:
> When performing a fallocate hole punch, set up a hugetlb_falloc struct
> and make i_private point to it. i_private will point to this struct for
> the duration of the operation. At the end of the operation, wake up
> anyone who faulted on the hole and is on the waitq.
>
> ...
>
> --- a/fs/hugetlbfs/inode.c
> +++ b/fs/hugetlbfs/inode.c
> @@ -507,7 +507,9 @@ static long hugetlbfs_punch_hole(struct inode *inode, loff_t offset, loff_t len)
> {
> struct hstate *h = hstate_inode(inode);
> loff_t hpage_size = huge_page_size(h);
> + unsigned long hpage_shift = huge_page_shift(h);
> loff_t hole_start, hole_end;
> + struct hugetlb_falloc hugetlb_falloc;
>
> /*
> * For hole punch round up the beginning offset of the hole and
> @@ -518,8 +520,23 @@ static long hugetlbfs_punch_hole(struct inode *inode, loff_t offset, loff_t len)
>
> if (hole_end > hole_start) {
> struct address_space *mapping = inode->i_mapping;
> + DECLARE_WAIT_QUEUE_HEAD_ONSTACK(hugetlb_falloc_waitq);
> +
> + /*
> + * Page faults on the area to be hole punched must be
> + * stopped during the operation. Initialize struct and
> + * have inode->i_private point to it.
> + */
> + hugetlb_falloc.waitq = &hugetlb_falloc_waitq;
> + hugetlb_falloc.start = hole_start >> hpage_shift;
> + hugetlb_falloc.end = hole_end >> hpage_shift;
This is a bit neater:
--- a/fs/hugetlbfs/inode.c~mm-hugetlb-setup-hugetlb_falloc-during-fallocate-hole-punch-fix
+++ a/fs/hugetlbfs/inode.c
@@ -509,7 +509,6 @@ static long hugetlbfs_punch_hole(struct
loff_t hpage_size = huge_page_size(h);
unsigned long hpage_shift = huge_page_shift(h);
loff_t hole_start, hole_end;
- struct hugetlb_falloc hugetlb_falloc;
/*
* For hole punch round up the beginning offset of the hole and
@@ -521,15 +520,16 @@ static long hugetlbfs_punch_hole(struct
if (hole_end > hole_start) {
struct address_space *mapping = inode->i_mapping;
DECLARE_WAIT_QUEUE_HEAD_ONSTACK(hugetlb_falloc_waitq);
-
/*
- * Page faults on the area to be hole punched must be
- * stopped during the operation. Initialize struct and
- * have inode->i_private point to it.
+ * Page faults on the area to be hole punched must be stopped
+ * during the operation. Initialize struct and have
+ * inode->i_private point to it.
*/
- hugetlb_falloc.waitq = &hugetlb_falloc_waitq;
- hugetlb_falloc.start = hole_start >> hpage_shift;
- hugetlb_falloc.end = hole_end >> hpage_shift;
+ struct hugetlb_falloc hugetlb_falloc = {
+ .waitq = &hugetlb_falloc_waitq,
+ .start = hole_start >> hpage_shift,
+ .end = hole_end >> hpage_shift
+ };
mutex_lock(&inode->i_mutex);
> mutex_lock(&inode->i_mutex);
> +
> + spin_lock(&inode->i_lock);
> + inode->i_private = &hugetlb_falloc;
> + spin_unlock(&inode->i_lock);
Locking around a single atomic assignment is a bit peculiar. I can
kinda see that it kinda protects the logic in hugetlb_fault(), but I
would like to hear (in comment form) your description of how this logic
works?
> i_mmap_lock_write(mapping);
> if (!RB_EMPTY_ROOT(&mapping->i_mmap))
> hugetlb_vmdelete_list(&mapping->i_mmap,
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