@@ -3163,6 +3163,9 @@ ssize_t vfs_iocb_iter_write(struct file *file, struct kiocb *iocb,
struct iov_iter *iter);
/* fs/splice.c */
+ssize_t filemap_splice_read(struct file *in, loff_t *ppos,
+ struct pipe_inode_info *pipe,
+ size_t len, unsigned int flags);
extern ssize_t generic_file_splice_read(struct file *, loff_t *,
struct pipe_inode_info *, size_t, unsigned int);
extern ssize_t iter_file_splice_write(struct pipe_inode_info *,
@@ -42,6 +42,8 @@
#include <linux/ramfs.h>
#include <linux/page_idle.h>
#include <linux/migrate.h>
+#include <linux/pipe_fs_i.h>
+#include <linux/splice.h>
#include <asm/pgalloc.h>
#include <asm/tlbflush.h>
#include "internal.h"
@@ -2842,6 +2844,132 @@ generic_file_read_iter(struct kiocb *iocb, struct iov_iter *iter)
}
EXPORT_SYMBOL(generic_file_read_iter);
+/*
+ * Splice subpages from a folio into a pipe.
+ */
+size_t splice_folio_into_pipe(struct pipe_inode_info *pipe,
+ struct folio *folio, loff_t fpos, size_t size)
+{
+ struct page *page;
+ size_t spliced = 0, offset = offset_in_folio(folio, fpos);
+
+ page = folio_page(folio, offset / PAGE_SIZE);
+ size = min(size, folio_size(folio) - offset);
+ offset %= PAGE_SIZE;
+
+ while (spliced < size &&
+ !pipe_full(pipe->head, pipe->tail, pipe->max_usage)) {
+ struct pipe_buffer *buf = pipe_head_buf(pipe);
+ size_t part = min_t(size_t, PAGE_SIZE - offset, size - spliced);
+
+ *buf = (struct pipe_buffer) {
+ .ops = &page_cache_pipe_buf_ops,
+ .page = page,
+ .offset = offset,
+ .len = part,
+ };
+ folio_get(folio);
+ pipe->head++;
+ page++;
+ spliced += part;
+ offset = 0;
+ }
+
+ return spliced;
+}
+
+/*
+ * Splice folios from the pagecache of a buffered (ie. non-O_DIRECT) file into
+ * a pipe.
+ */
+ssize_t filemap_splice_read(struct file *in, loff_t *ppos,
+ struct pipe_inode_info *pipe,
+ size_t len, unsigned int flags)
+{
+ struct folio_batch fbatch;
+ struct kiocb iocb;
+ size_t total_spliced = 0, used, npages;
+ loff_t isize, end_offset;
+ bool writably_mapped;
+ int i, error = 0;
+
+ init_sync_kiocb(&iocb, in);
+ iocb.ki_pos = *ppos;
+
+ /* Work out how much data we can actually add into the pipe */
+ used = pipe_occupancy(pipe->head, pipe->tail);
+ npages = max_t(ssize_t, pipe->max_usage - used, 0);
+ len = min_t(size_t, len, npages * PAGE_SIZE);
+
+ folio_batch_init(&fbatch);
+
+ do {
+ cond_resched();
+
+ if (*ppos >= i_size_read(file_inode(in)))
+ break;
+
+ iocb.ki_pos = *ppos;
+ error = filemap_get_pages(&iocb, len, &fbatch, true);
+ if (error < 0)
+ break;
+
+ /*
+ * i_size must be checked after we know the pages are Uptodate.
+ *
+ * Checking i_size after the check allows us to calculate
+ * the correct value for "nr", which means the zero-filled
+ * part of the page is not copied back to userspace (unless
+ * another truncate extends the file - this is desired though).
+ */
+ isize = i_size_read(file_inode(in));
+ if (unlikely(*ppos >= isize))
+ break;
+ end_offset = min_t(loff_t, isize, *ppos + len);
+
+ /*
+ * Once we start copying data, we don't want to be touching any
+ * cachelines that might be contended:
+ */
+ writably_mapped = mapping_writably_mapped(in->f_mapping);
+
+ for (i = 0; i < folio_batch_count(&fbatch); i++) {
+ struct folio *folio = fbatch.folios[i];
+ size_t n;
+
+ if (folio_pos(folio) >= end_offset)
+ goto out;
+ folio_mark_accessed(folio);
+
+ /*
+ * If users can be writing to this folio using arbitrary
+ * virtual addresses, take care of potential aliasing
+ * before reading the folio on the kernel side.
+ */
+ if (writably_mapped)
+ flush_dcache_folio(folio);
+
+ n = splice_folio_into_pipe(pipe, folio, *ppos, len);
+ if (!n)
+ goto out;
+ len -= n;
+ total_spliced += n;
+ *ppos += n;
+ in->f_ra.prev_pos = *ppos;
+ if (pipe_full(pipe->head, pipe->tail, pipe->max_usage))
+ goto out;
+ }
+
+ folio_batch_release(&fbatch);
+ } while (len);
+
+out:
+ folio_batch_release(&fbatch);
+ file_accessed(in);
+
+ return total_spliced ? total_spliced : error;
+}
+
static inline loff_t folio_seek_hole_data(struct xa_state *xas,
struct address_space *mapping, struct folio *folio,
loff_t start, loff_t end, bool seek_data)
@@ -794,6 +794,12 @@ struct migration_target_control {
gfp_t gfp_mask;
};
+/*
+ * mm/filemap.c
+ */
+size_t splice_folio_into_pipe(struct pipe_inode_info *pipe,
+ struct folio *folio, loff_t fpos, size_t size);
+
/*
* mm/vmalloc.c
*/