[RFC PATCH 1/9] splice: don't check for uptodate if partially uptodate is impl

Daniel Gomez
2024-02-09T14:29:12Z

From: Pankaj Raghav <p.raghav@samsung.com>

When huge_page=always is set in tmpfs, it will zero out the whole page even
if only a small part of it is written, and it updates the uptodate flag of the
whole huge page.

Once the per-block uptodate tracking is implemented for tmpfs hugepages,
pipe_buf_confirm only needs to check the range it needs to splice to be
uptodate and not the whole folio as we don't set uptodate flag for partial
writes.

Signed-off-by: Pankaj Raghav <p.raghav@samsung.com>
Signed-off-by: Daniel Gomez <da.gomez@samsung.com>
---

Other option here is to have a separate implementation of
page_cache_pipe_buf_ops for tmpfs instead of changing the
page_cache_pipe_buf_confirm.

fs/splice.c | 17 ++++++++++++++---
1 file changed, 14 insertions(+), 3 deletions(-)

diff --git a/fs/splice.c b/fs/splice.c
index 218e24b1ac40..e6ac57795590 100644
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -120,7 +120,9 @@ static int page_cache_pipe_buf_confirm(struct pipe_inode_info *pipe,
struct pipe_buffer *buf)
{
struct folio *folio = page_folio(buf->page);
+ const struct address_space_operations *ops;
int err;
+ off_t off = folio_page_idx(folio, buf->page) * PAGE_SIZE + buf->offset;

if (!folio_test_uptodate(folio)) {
folio_lock(folio);
@@ -134,12 +136,21 @@ static int page_cache_pipe_buf_confirm(struct pipe_inode_info *pipe,
goto error;
}

+ ops = folio->mapping->a_ops;
/*
* Uh oh, read-error from disk.
*/
- if (!folio_test_uptodate(folio)) {
- err = -EIO;
- goto error;
+ if (!ops->is_partially_uptodate) {
+ if (!folio_test_uptodate(folio)) {
+ err = -EIO;
+ goto error;
+ }
+ } else {
+ if (!ops->is_partially_uptodate(folio, off,
+ buf->len)) {
+ err = -EIO;
+ goto error;
+ }
}

/* Folio is ok after all, we are done */
--
2.43.0