[PATCH] splice: improve writeback and clean up page stealing
By cleaning up the writeback logic (killing write_one_page() and the manual
set_page_dirty()), we can get rid of ->stolen inside the pipe_buffer and
just keep it local in pipe_to_file().
This also adds dirty page balancing logic and O_SYNC handling.
Signed-off-by: Jens Axboe <axboe@suse.de>
diff --git a/fs/splice.c b/fs/splice.c
index a555d0a..07f4d86 100644
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -22,7 +22,10 @@
#include <linux/pipe_fs_i.h>
#include <linux/mm_inline.h>
#include <linux/swap.h>
+#include <linux/writeback.h>
+#include <linux/buffer_head.h>
#include <linux/module.h>
+#include <linux/syscalls.h>
/*
* Passed to the actors
@@ -38,11 +41,15 @@
struct pipe_buffer *buf)
{
struct page *page = buf->page;
+ struct address_space *mapping = page_mapping(page);
WARN_ON(!PageLocked(page));
WARN_ON(!PageUptodate(page));
- if (!remove_mapping(page_mapping(page), page))
+ if (PagePrivate(page))
+ try_to_release_page(page, mapping_gfp_mask(mapping));
+
+ if (!remove_mapping(mapping, page))
return 1;
if (PageLRU(page)) {
@@ -55,7 +62,6 @@
spin_unlock_irq(&zone->lru_lock);
}
- buf->stolen = 1;
return 0;
}
@@ -64,7 +70,6 @@
{
page_cache_release(buf->page);
buf->page = NULL;
- buf->stolen = 0;
}
static void *page_cache_pipe_buf_map(struct file *file,
@@ -91,8 +96,7 @@
static void page_cache_pipe_buf_unmap(struct pipe_inode_info *info,
struct pipe_buffer *buf)
{
- if (!buf->stolen)
- unlock_page(buf->page);
+ unlock_page(buf->page);
kunmap(buf->page);
}
@@ -319,7 +323,8 @@
}
/*
- * Send 'len' bytes to socket from 'file' at position 'pos' using sendpage().
+ * Send 'sd->len' bytes to socket from 'sd->file' at position 'sd->pos'
+ * using sendpage().
*/
static int pipe_to_sendpage(struct pipe_inode_info *info,
struct pipe_buffer *buf, struct splice_desc *sd)
@@ -379,7 +384,7 @@
struct page *page;
pgoff_t index;
char *src;
- int ret;
+ int ret, stolen;
/*
* after this, page will be locked and unmapped
@@ -390,6 +395,7 @@
index = sd->pos >> PAGE_CACHE_SHIFT;
offset = sd->pos & ~PAGE_CACHE_MASK;
+ stolen = 0;
/*
* reuse buf page, if SPLICE_F_MOVE is set
@@ -399,6 +405,7 @@
goto find_page;
page = buf->page;
+ stolen = 1;
if (add_to_page_cache_lru(page, mapping, index,
mapping_gfp_mask(mapping)))
goto find_page;
@@ -443,10 +450,13 @@
}
ret = mapping->a_ops->prepare_write(file, page, 0, sd->len);
- if (ret)
+ if (ret == AOP_TRUNCATED_PAGE) {
+ page_cache_release(page);
+ goto find_page;
+ } else if (ret)
goto out;
- if (!buf->stolen) {
+ if (!stolen) {
char *dst = kmap_atomic(page, KM_USER0);
memcpy(dst + offset, src + buf->offset, sd->len);
@@ -455,16 +465,18 @@
}
ret = mapping->a_ops->commit_write(file, page, 0, sd->len);
- if (ret < 0)
+ if (ret == AOP_TRUNCATED_PAGE) {
+ page_cache_release(page);
+ goto find_page;
+ } else if (ret)
goto out;
- set_page_dirty(page);
- ret = write_one_page(page, 0);
+ balance_dirty_pages_ratelimited(mapping);
out:
- if (ret < 0)
- unlock_page(page);
- if (!buf->stolen)
+ if (!stolen) {
page_cache_release(page);
+ unlock_page(page);
+ }
buf->ops->unmap(info, buf);
return ret;
}
@@ -576,7 +588,27 @@
ssize_t generic_file_splice_write(struct inode *inode, struct file *out,
size_t len, unsigned int flags)
{
- return move_from_pipe(inode, out, len, flags, pipe_to_file);
+ struct address_space *mapping = out->f_mapping;
+ ssize_t ret = move_from_pipe(inode, out, len, flags, pipe_to_file);
+
+ /*
+ * if file or inode is SYNC and we actually wrote some data, sync it
+ */
+ if (unlikely((out->f_flags & O_SYNC) || IS_SYNC(mapping->host))
+ && ret > 0) {
+ struct inode *inode = mapping->host;
+ int err;
+
+ mutex_lock(&inode->i_mutex);
+ err = generic_osync_inode(mapping->host, mapping,
+ OSYNC_METADATA|OSYNC_DATA);
+ mutex_unlock(&inode->i_mutex);
+
+ if (err)
+ ret = err;
+ }
+
+ return ret;
}
ssize_t generic_splice_sendpage(struct inode *inode, struct file *out,
