On 5/27/24 23:36, Christoph Hellwig wrote:
From: "Matthew Wilcox (Oracle)" <willy@xxxxxxxxxxxxx>
Modelled after the loop in iomap_write_iter(), copy larger chunks from
userspace if the filesystem has created large folios.
Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
[hch: use mapping_max_folio_size to keep supporting file systems that do
not support large folios]
Signed-off-by: Christoph Hellwig <hch@xxxxxx>
---
mm/filemap.c | 40 +++++++++++++++++++++++++---------------
1 file changed, 25 insertions(+), 15 deletions(-)
diff --git a/mm/filemap.c b/mm/filemap.c
index 382c3d06bfb10c..860728e26ccf32 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -3981,21 +3981,24 @@ ssize_t generic_perform_write(struct kiocb *iocb, struct iov_iter *i)
loff_t pos = iocb->ki_pos;
struct address_space *mapping = file->f_mapping;
const struct address_space_operations *a_ops = mapping->a_ops;
+ size_t chunk = mapping_max_folio_size(mapping);
Better to default chunk to PAGE_SIZE for backward compat
+ size_t chunk = PAGE_SIZE;
long status = 0;
ssize_t written = 0;
Have fs opt in to large folio support:
+ if (mapping_large_folio_support(mapping))
+ chunk = PAGE_SIZE << MAX_PAGECACHE_ORDER;
do {
struct page *page;
- unsigned long offset; /* Offset into pagecache page */
- unsigned long bytes; /* Bytes to write to page */
+ struct folio *folio;
+ size_t offset; /* Offset into folio */
+ size_t bytes; /* Bytes to write to folio */
size_t copied; /* Bytes copied from user */
void *fsdata = NULL;
- offset = (pos & (PAGE_SIZE - 1));
- bytes = min_t(unsigned long, PAGE_SIZE - offset,
- iov_iter_count(i));
+ bytes = iov_iter_count(i);
+retry:
+ offset = pos & (chunk - 1);
+ bytes = min(chunk - offset, bytes);
+ balance_dirty_pages_ratelimited(mapping);
-again:
/*
* Bring in the user page that we will copy from _first_.
* Otherwise there's a nasty deadlock on copying from the
@@ -4017,11 +4020,16 @@ ssize_t generic_perform_write(struct kiocb *iocb, struct iov_iter *i)
if (unlikely(status < 0))
break;
+ folio = page_folio(page);
+ offset = offset_in_folio(folio, pos);
+ if (bytes > folio_size(folio) - offset)
+ bytes = folio_size(folio) - offset;
+
if (mapping_writably_mapped(mapping))
- flush_dcache_page(page);
+ flush_dcache_folio(folio);
- copied = copy_page_from_iter_atomic(page, offset, bytes, i);
- flush_dcache_page(page);
+ copied = copy_folio_from_iter_atomic(folio, offset, bytes, i);
+ flush_dcache_folio(folio);
status = a_ops->write_end(file, mapping, pos, bytes, copied,
page, fsdata);
@@ -4039,14 +4047,16 @@ ssize_t generic_perform_write(struct kiocb *iocb, struct iov_iter *i)
* halfway through, might be a race with munmap,
* might be severe memory pressure.
*/
- if (copied)
+ if (chunk > PAGE_SIZE)
+ chunk /= 2;
+ if (copied) {
bytes = copied;
- goto again;
+ goto retry;
+ }
+ } else {
+ pos += status;
+ written += status;
}
- pos += status;
- written += status;
-
- balance_dirty_pages_ratelimited(mapping);
} while (iov_iter_count(i));
if (!written)
Tested with Lustre with large folios and kernel 6.6 with this patch (and suggested changes).
Tested-by: Shaun Tancheff <shaun.tancheff@xxxxxxx>
