Add mapping_get_read_heads() which returns the head pages which
represent a contiguous array of bytes in the file. It also stops
when encountering a page marked as Readahead or !Uptodate (but
does return that page) so it can be handled appropriately by
gfbr_get_pages().
Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
---
mm/filemap.c | 78 ++++++++++++++++++++++++++++++++++++++++------------
1 file changed, 61 insertions(+), 17 deletions(-)
diff --git a/mm/filemap.c b/mm/filemap.c
index 1bfd87d85bfd..c0161f42f37d 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -2166,6 +2166,48 @@ static void shrink_readahead_size_eio(struct file_ra_state *ra)
ra->ra_pages /= 4;
}
+static unsigned mapping_get_read_heads(struct address_space *mapping,
+ pgoff_t index, unsigned int nr_pages, struct page **pages)
+{
+ XA_STATE(xas, &mapping->i_pages, index);
+ struct page *head;
+ unsigned int ret = 0;
+
+ if (unlikely(!nr_pages))
+ return 0;
+
+ rcu_read_lock();
+ for (head = xas_load(&xas); head; head = xas_next(&xas)) {
+ if (xas_retry(&xas, head))
+ continue;
+ if (xa_is_value(head))
+ break;
+ if (!page_cache_get_speculative(head))
+ goto retry;
+
+ /* Has the page moved or been split? */
+ if (unlikely(head != xas_reload(&xas)))
+ goto put_page;
+
+ pages[ret++] = head;
+ if (ret == nr_pages)
+ break;
+ if (!PageUptodate(head))
+ break;
+ if (PageReadahead(head))
+ break;
+ xas.xa_index = head->index + thp_nr_pages(head) - 1;
+ xas.xa_offset = (xas.xa_index >> xas.xa_shift) & XA_CHUNK_MASK;
+ continue;
+put_page:
+ put_page(head);
+retry:
+ xas_reset(&xas);
+ }
+ rcu_read_unlock();
+ return ret;
+}
+
static int lock_page_for_iocb(struct kiocb *iocb, struct page *page)
{
if (iocb->ki_flags & IOCB_WAITQ)
@@ -2328,14 +2370,14 @@ static int gfbr_get_pages(struct kiocb *iocb, struct iov_iter *iter,
struct file_ra_state *ra = &filp->f_ra;
pgoff_t index = iocb->ki_pos >> PAGE_SHIFT;
pgoff_t last_index = (iocb->ki_pos + iter->count + PAGE_SIZE-1) >> PAGE_SHIFT;
- int i, j, nr_got, err = 0;
+ int i, nr_got, err = 0;
nr = min_t(unsigned long, last_index - index, nr);
find_page:
if (fatal_signal_pending(current))
return -EINTR;
- nr_got = find_get_pages_contig(mapping, index, nr, pages);
+ nr_got = mapping_get_read_heads(mapping, index, nr, pages);
if (nr_got)
goto got_pages;
@@ -2344,7 +2386,7 @@ static int gfbr_get_pages(struct kiocb *iocb, struct iov_iter *iter,
page_cache_sync_readahead(mapping, ra, filp, index, last_index - index);
- nr_got = find_get_pages_contig(mapping, index, nr, pages);
+ nr_got = mapping_get_read_heads(mapping, index, nr, pages);
if (nr_got)
goto got_pages;
@@ -2355,15 +2397,14 @@ static int gfbr_get_pages(struct kiocb *iocb, struct iov_iter *iter,
got_pages:
for (i = 0; i < nr_got; i++) {
struct page *page = pages[i];
- pgoff_t pg_index = index + i;
+ pgoff_t pg_index = page->index;
loff_t pg_pos = max(iocb->ki_pos,
(loff_t) pg_index << PAGE_SHIFT);
loff_t pg_count = iocb->ki_pos + iter->count - pg_pos;
if (PageReadahead(page)) {
if (iocb->ki_flags & IOCB_NOIO) {
- for (j = i; j < nr_got; j++)
- put_page(pages[j]);
+ put_page(page);
nr_got = i;
err = -EAGAIN;
break;
@@ -2375,8 +2416,7 @@ static int gfbr_get_pages(struct kiocb *iocb, struct iov_iter *iter,
if (!PageUptodate(page)) {
if ((iocb->ki_flags & IOCB_NOWAIT) ||
((iocb->ki_flags & IOCB_WAITQ) && i)) {
- for (j = i; j < nr_got; j++)
- put_page(pages[j]);
+ put_page(page);
nr_got = i;
err = -EAGAIN;
break;
@@ -2385,8 +2425,6 @@ static int gfbr_get_pages(struct kiocb *iocb, struct iov_iter *iter,
page = gfbr_update_page(iocb, mapping, iter, page,
pg_pos, pg_count);
if (IS_ERR_OR_NULL(page)) {
- for (j = i + 1; j < nr_got; j++)
- put_page(pages[j]);
nr_got = i;
err = PTR_ERR_OR_ZERO(page);
break;
@@ -2500,20 +2538,26 @@ ssize_t generic_file_buffered_read(struct kiocb *iocb,
mark_page_accessed(pages[i]);
for (i = 0; i < pg_nr; i++) {
- unsigned int offset = iocb->ki_pos & ~PAGE_MASK;
- unsigned int bytes = min_t(loff_t, end_offset - iocb->ki_pos,
- PAGE_SIZE - offset);
- unsigned int copied;
+ struct page *page = pages[i];
+ size_t page_size = thp_size(page);
+ size_t offset = iocb->ki_pos & (page_size - 1);
+ size_t bytes = min_t(loff_t, end_offset - iocb->ki_pos,
+ page_size - offset);
+ size_t copied;
/*
* If users can be writing to this page using arbitrary
* virtual addresses, take care about potential aliasing
* before reading the page on the kernel side.
*/
- if (writably_mapped)
- flush_dcache_page(pages[i]);
+ if (writably_mapped) {
+ int j;
+
+ for (j = 0; j < thp_nr_pages(page); j++)
+ flush_dcache_page(page + j);
+ }
- copied = copy_page_to_iter(pages[i], offset, bytes, iter);
+ copied = copy_page_to_iter(page, offset, bytes, iter);
written += copied;
iocb->ki_pos += copied;
--
2.28.0
