* [PATCH] fs: Support THPs in vfs_dedupe_file_range
@ 2020-09-15 14:46 Matthew Wilcox (Oracle)
2020-09-15 16:38 ` Darrick J. Wong
0 siblings, 1 reply; 2+ messages in thread
From: Matthew Wilcox (Oracle) @ 2020-09-15 14:46 UTC (permalink / raw)
To: Al Viro
Cc: Matthew Wilcox (Oracle), linux-fsdevel, Darrick J . Wong,
Bill O'Donnell
We may get tail pages returned from vfs_dedupe_get_page(). If we do,
we have to call page_mapping() instead of dereferencing page->mapping
directly. We may also deadlock trying to lock the page twice if they're
subpages of the same THP, so compare the head pages instead.
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---
fs/read_write.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)
diff --git a/fs/read_write.c b/fs/read_write.c
index 5db58b8c78d0..c4d5eb47a21e 100644
--- a/fs/read_write.c
+++ b/fs/read_write.c
@@ -1906,6 +1906,8 @@ static struct page *vfs_dedupe_get_page(struct inode *inode, loff_t offset)
*/
static void vfs_lock_two_pages(struct page *page1, struct page *page2)
{
+ page1 = thp_head(page1);
+ page2 = thp_head(page2);
/* Always lock in order of increasing index. */
if (page1->index > page2->index)
swap(page1, page2);
@@ -1918,6 +1920,8 @@ static void vfs_lock_two_pages(struct page *page1, struct page *page2)
/* Unlock two pages, being careful not to unlock the same page twice. */
static void vfs_unlock_two_pages(struct page *page1, struct page *page2)
{
+ page1 = thp_head(page1);
+ page2 = thp_head(page2);
unlock_page(page1);
if (page1 != page2)
unlock_page(page2);
@@ -1972,8 +1976,8 @@ static int vfs_dedupe_file_range_compare(struct inode *src, loff_t srcoff,
* someone is invalidating pages on us and we lose.
*/
if (!PageUptodate(src_page) || !PageUptodate(dest_page) ||
- src_page->mapping != src->i_mapping ||
- dest_page->mapping != dest->i_mapping) {
+ page_mapping(src_page) != src->i_mapping ||
+ page_mapping(dest_page) != dest->i_mapping) {
same = false;
goto unlock;
}
--
2.28.0
^ permalink raw reply related [flat|nested] 2+ messages in thread* Re: [PATCH] fs: Support THPs in vfs_dedupe_file_range
2020-09-15 14:46 [PATCH] fs: Support THPs in vfs_dedupe_file_range Matthew Wilcox (Oracle)
@ 2020-09-15 16:38 ` Darrick J. Wong
0 siblings, 0 replies; 2+ messages in thread
From: Darrick J. Wong @ 2020-09-15 16:38 UTC (permalink / raw)
To: Matthew Wilcox (Oracle); +Cc: Al Viro, linux-fsdevel, Bill O'Donnell
On Tue, Sep 15, 2020 at 03:46:16PM +0100, Matthew Wilcox (Oracle) wrote:
> We may get tail pages returned from vfs_dedupe_get_page(). If we do,
> we have to call page_mapping() instead of dereferencing page->mapping
> directly. We may also deadlock trying to lock the page twice if they're
> subpages of the same THP, so compare the head pages instead.
>
> Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Seems fine to me...
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
--D
> ---
> fs/read_write.c | 8 ++++++--
> 1 file changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/fs/read_write.c b/fs/read_write.c
> index 5db58b8c78d0..c4d5eb47a21e 100644
> --- a/fs/read_write.c
> +++ b/fs/read_write.c
> @@ -1906,6 +1906,8 @@ static struct page *vfs_dedupe_get_page(struct inode *inode, loff_t offset)
> */
> static void vfs_lock_two_pages(struct page *page1, struct page *page2)
> {
> + page1 = thp_head(page1);
> + page2 = thp_head(page2);
> /* Always lock in order of increasing index. */
> if (page1->index > page2->index)
> swap(page1, page2);
> @@ -1918,6 +1920,8 @@ static void vfs_lock_two_pages(struct page *page1, struct page *page2)
> /* Unlock two pages, being careful not to unlock the same page twice. */
> static void vfs_unlock_two_pages(struct page *page1, struct page *page2)
> {
> + page1 = thp_head(page1);
> + page2 = thp_head(page2);
> unlock_page(page1);
> if (page1 != page2)
> unlock_page(page2);
> @@ -1972,8 +1976,8 @@ static int vfs_dedupe_file_range_compare(struct inode *src, loff_t srcoff,
> * someone is invalidating pages on us and we lose.
> */
> if (!PageUptodate(src_page) || !PageUptodate(dest_page) ||
> - src_page->mapping != src->i_mapping ||
> - dest_page->mapping != dest->i_mapping) {
> + page_mapping(src_page) != src->i_mapping ||
> + page_mapping(dest_page) != dest->i_mapping) {
> same = false;
> goto unlock;
> }
> --
> 2.28.0
>
^ permalink raw reply [flat|nested] 2+ messages in thread
end of thread, other threads:[~2020-09-15 22:14 UTC | newest]
Thread overview: 2+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2020-09-15 14:46 [PATCH] fs: Support THPs in vfs_dedupe_file_range Matthew Wilcox (Oracle)
2020-09-15 16:38 ` Darrick J. Wong
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).