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iomap: Copy larger chunks from userspace 

If we have a large folio, we can copy in larger chunks than PAGE_SIZE.
Start at the maximum page cache size and shrink by half every time we
hit the "we are short on memory" problem.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
This commit is contained in:
Matthew Wilcox (Oracle) 2023-05-20 12:13:20 -04:00
parent d6bb59a944
commit 5d8edfb900
1 changed files with 17 additions and 15 deletions
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28
fs/iomap/buffered-io.c
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@ -769,6 +769,7 @@ static size_t iomap_write_end(struct iomap_iter *iter, loff_t pos, size_t len,
static loff_t iomap_write_iter(struct iomap_iter *iter, struct iov_iter *i)
{
loff_t length = iomap_length(iter);
size_t chunk = PAGE_SIZE << MAX_PAGECACHE_ORDER;
loff_t pos = iter->pos;
ssize_t written = 0;
long status = 0;
@ -777,15 +778,12 @@ static loff_t iomap_write_iter(struct iomap_iter *iter, struct iov_iter *i)
do {
struct folio *folio;
struct page *page;
unsigned long offset; /* Offset into pagecache page */
unsigned long bytes; /* Bytes to write to page */
size_t offset; /* Offset into folio */
size_t bytes; /* Bytes to write to folio */
size_t copied; /* Bytes copied from user */
offset = offset_in_page(pos);
bytes = min_t(unsigned long, PAGE_SIZE - offset,
iov_iter_count(i));
again:
offset = pos & (chunk - 1);
bytes = min(chunk - offset, iov_iter_count(i));
status = balance_dirty_pages_ratelimited_flags(mapping,
bdp_flags);
if (unlikely(status))
@ -815,12 +813,14 @@ again:
if (iter->iomap.flags & IOMAP_F_STALE)
break;
page = folio_file_page(folio, pos >> PAGE_SHIFT);
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);
copied = copy_page_from_iter_atomic(page, offset, bytes, i);
flush_dcache_folio(folio);
copied = copy_folio_from_iter_atomic(folio, offset, bytes, i);
status = iomap_write_end(iter, pos, bytes, copied, folio);
if (unlikely(copied != status))
@ -836,11 +836,13 @@ again:
*/
if (copied)
bytes = copied;
goto again;
}
if (chunk > PAGE_SIZE)
chunk /= 2;
} else {
pos += status;
written += status;
length -= status;
}
} while (iov_iter_count(i) && length);
if (status == -EAGAIN) {