Merge branch 'splice' of git://brick.kernel.dk/data/git/linux-2.6-block
* 'splice' of git://brick.kernel.dk/data/git/linux-2.6-block:
[PATCH] splice: fix page stealing LRU handling.
[PATCH] splice: page stealing needs to wait_on_page_writeback()
[PATCH] splice: export generic_splice_sendpage
[PATCH] splice: add a SPLICE_F_MORE flag
[PATCH] splice: add comments documenting more of the code
[PATCH] splice: improve writeback and clean up page stealing
[PATCH] splice: fix shadow[] filling logic
diff --git a/fs/pipe.c b/fs/pipe.c
index 109a102..795df98 100644
--- a/fs/pipe.c
+++ b/fs/pipe.c
@@ -95,6 +95,8 @@
{
struct page *page = buf->page;
+ buf->flags &= ~PIPE_BUF_FLAG_STOLEN;
+
/*
* If nobody else uses this page, and we don't already have a
* temporary page, let's keep track of it as a one-deep
@@ -124,7 +126,7 @@
static int anon_pipe_buf_steal(struct pipe_inode_info *info,
struct pipe_buffer *buf)
{
- buf->stolen = 1;
+ buf->flags |= PIPE_BUF_FLAG_STOLEN;
return 0;
}
diff --git a/fs/splice.c b/fs/splice.c
index 6081cf7..bfa42a2 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
@@ -34,28 +37,37 @@
loff_t pos; /* file position */
};
+/*
+ * Attempt to steal a page from a pipe buffer. This should perhaps go into
+ * a vm helper function, it's already simplified quite a bit by the
+ * addition of remove_mapping(). If success is returned, the caller may
+ * attempt to reuse this page for another destination.
+ */
static int page_cache_pipe_buf_steal(struct pipe_inode_info *info,
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))
+ /*
+ * At least for ext2 with nobh option, we need to wait on writeback
+ * completing on this page, since we'll remove it from the pagecache.
+ * Otherwise truncate wont wait on the page, allowing the disk
+ * blocks to be reused by someone else before we actually wrote our
+ * data to them. fs corruption ensues.
+ */
+ wait_on_page_writeback(page);
+
+ if (PagePrivate(page))
+ try_to_release_page(page, mapping_gfp_mask(mapping));
+
+ if (!remove_mapping(mapping, page))
return 1;
- if (PageLRU(page)) {
- struct zone *zone = page_zone(page);
-
- spin_lock_irq(&zone->lru_lock);
- BUG_ON(!PageLRU(page));
- __ClearPageLRU(page);
- del_page_from_lru(zone, page);
- spin_unlock_irq(&zone->lru_lock);
- }
-
- buf->stolen = 1;
+ buf->flags |= PIPE_BUF_FLAG_STOLEN | PIPE_BUF_FLAG_LRU;
return 0;
}
@@ -64,7 +76,7 @@
{
page_cache_release(buf->page);
buf->page = NULL;
- buf->stolen = 0;
+ buf->flags &= ~(PIPE_BUF_FLAG_STOLEN | PIPE_BUF_FLAG_LRU);
}
static void *page_cache_pipe_buf_map(struct file *file,
@@ -91,8 +103,7 @@
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);
}
@@ -104,6 +115,10 @@
.steal = page_cache_pipe_buf_steal,
};
+/*
+ * Pipe output worker. This sets up our pipe format with the page cache
+ * pipe buffer operations. Otherwise very similar to the regular pipe_writev().
+ */
static ssize_t move_to_pipe(struct inode *inode, struct page **pages,
int nr_pages, unsigned long offset,
unsigned long len, unsigned int flags)
@@ -237,9 +252,9 @@
* fill shadow[] with pages at the right locations, so we only
* have to fill holes
*/
- memset(shadow, 0, i * sizeof(struct page *));
- for (j = 0, pidx = index; j < i; pidx++, j++)
- shadow[pages[j]->index - pidx] = pages[j];
+ memset(shadow, 0, nr_pages * sizeof(struct page *));
+ for (j = 0; j < i; j++)
+ shadow[pages[j]->index - index] = pages[j];
/*
* now fill in the holes
@@ -288,6 +303,16 @@
return move_to_pipe(pipe, pages, i, offset, len, flags);
}
+/**
+ * generic_file_splice_read - splice data from file to a pipe
+ * @in: file to splice from
+ * @pipe: pipe to splice to
+ * @len: number of bytes to splice
+ * @flags: splice modifier flags
+ *
+ * Will read pages from given file and fill them into a pipe.
+ *
+ */
ssize_t generic_file_splice_read(struct file *in, struct inode *pipe,
size_t len, unsigned int flags)
{
@@ -318,8 +343,11 @@
return ret;
}
+EXPORT_SYMBOL(generic_file_splice_read);
+
/*
- * 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)
@@ -329,6 +357,7 @@
unsigned int offset;
ssize_t ret;
void *ptr;
+ int more;
/*
* sub-optimal, but we are limited by the pipe ->map. we don't
@@ -341,9 +370,9 @@
return PTR_ERR(ptr);
offset = pos & ~PAGE_CACHE_MASK;
+ more = (sd->flags & SPLICE_F_MORE) || sd->len < sd->total_len;
- ret = file->f_op->sendpage(file, buf->page, offset, sd->len, &pos,
- sd->len < sd->total_len);
+ ret = file->f_op->sendpage(file, buf->page, offset, sd->len, &pos,more);
buf->ops->unmap(info, buf);
if (ret == sd->len)
@@ -365,16 +394,19 @@
* - Destination page does not exist, we can add the pipe page to
* the page cache and avoid the copy.
*
- * For now we just do the slower thing and always copy pages over, it's
- * easier than migrating pages from the pipe to the target file. For the
- * case of doing file | file splicing, the migrate approach had some LRU
- * nastiness...
+ * If asked to move pages to the output file (SPLICE_F_MOVE is set in
+ * sd->flags), we attempt to migrate pages from the pipe to the output
+ * file address space page cache. This is possible if no one else has
+ * the pipe page referenced outside of the pipe and page cache. If
+ * SPLICE_F_MOVE isn't set, or we cannot move the page, we simply create
+ * a new page in the output file page cache and fill/dirty that.
*/
static int pipe_to_file(struct pipe_inode_info *info, struct pipe_buffer *buf,
struct splice_desc *sd)
{
struct file *file = sd->file;
struct address_space *mapping = file->f_mapping;
+ gfp_t gfp_mask = mapping_gfp_mask(mapping);
unsigned int offset;
struct page *page;
pgoff_t index;
@@ -395,18 +427,23 @@
* reuse buf page, if SPLICE_F_MOVE is set
*/
if (sd->flags & SPLICE_F_MOVE) {
+ /*
+ * If steal succeeds, buf->page is now pruned from the vm
+ * side (LRU and page cache) and we can reuse it.
+ */
if (buf->ops->steal(info, buf))
goto find_page;
page = buf->page;
- if (add_to_page_cache_lru(page, mapping, index,
- mapping_gfp_mask(mapping)))
+ if (add_to_page_cache(page, mapping, index, gfp_mask))
goto find_page;
+
+ if (!(buf->flags & PIPE_BUF_FLAG_LRU))
+ lru_cache_add(page);
} else {
find_page:
ret = -ENOMEM;
- page = find_or_create_page(mapping, index,
- mapping_gfp_mask(mapping));
+ page = find_or_create_page(mapping, index, gfp_mask);
if (!page)
goto out;
@@ -443,10 +480,13 @@
}
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 (!(buf->flags & PIPE_BUF_FLAG_STOLEN)) {
char *dst = kmap_atomic(page, KM_USER0);
memcpy(dst + offset, src + buf->offset, sd->len);
@@ -455,16 +495,18 @@
}
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 (!(buf->flags & PIPE_BUF_FLAG_STOLEN)) {
page_cache_release(page);
+ unlock_page(page);
+ }
buf->ops->unmap(info, buf);
return ret;
}
@@ -472,6 +514,11 @@
typedef int (splice_actor)(struct pipe_inode_info *, struct pipe_buffer *,
struct splice_desc *);
+/*
+ * Pipe input worker. Most of this logic works like a regular pipe, the
+ * key here is the 'actor' worker passed in that actually moves the data
+ * to the wanted destination. See pipe_to_file/pipe_to_sendpage above.
+ */
static ssize_t move_from_pipe(struct inode *inode, struct file *out,
size_t len, unsigned int flags,
splice_actor *actor)
@@ -573,21 +620,67 @@
}
+/**
+ * generic_file_splice_write - splice data from a pipe to a file
+ * @inode: pipe inode
+ * @out: file to write to
+ * @len: number of bytes to splice
+ * @flags: splice modifier flags
+ *
+ * Will either move or copy pages (determined by @flags options) from
+ * the given pipe inode to the given file.
+ *
+ */
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;
}
+EXPORT_SYMBOL(generic_file_splice_write);
+
+/**
+ * generic_splice_sendpage - splice data from a pipe to a socket
+ * @inode: pipe inode
+ * @out: socket to write to
+ * @len: number of bytes to splice
+ * @flags: splice modifier flags
+ *
+ * Will send @len bytes from the pipe to a network socket. No data copying
+ * is involved.
+ *
+ */
ssize_t generic_splice_sendpage(struct inode *inode, struct file *out,
size_t len, unsigned int flags)
{
return move_from_pipe(inode, out, len, flags, pipe_to_sendpage);
}
-EXPORT_SYMBOL(generic_file_splice_write);
-EXPORT_SYMBOL(generic_file_splice_read);
+EXPORT_SYMBOL(generic_splice_sendpage);
+/*
+ * Attempt to initiate a splice from pipe to file.
+ */
static long do_splice_from(struct inode *pipe, struct file *out, size_t len,
unsigned int flags)
{
@@ -608,6 +701,9 @@
return out->f_op->splice_write(pipe, out, len, flags);
}
+/*
+ * Attempt to initiate a splice from a file to a pipe.
+ */
static long do_splice_to(struct file *in, struct inode *pipe, size_t len,
unsigned int flags)
{
@@ -636,6 +732,9 @@
return in->f_op->splice_read(in, pipe, len, flags);
}
+/*
+ * Determine where to splice to/from.
+ */
static long do_splice(struct file *in, struct file *out, size_t len,
unsigned int flags)
{
diff --git a/include/linux/pipe_fs_i.h b/include/linux/pipe_fs_i.h
index d218fc7..ec38495 100644
--- a/include/linux/pipe_fs_i.h
+++ b/include/linux/pipe_fs_i.h
@@ -5,11 +5,14 @@
#define PIPE_BUFFERS (16)
+#define PIPE_BUF_FLAG_STOLEN 0x01
+#define PIPE_BUF_FLAG_LRU 0x02
+
struct pipe_buffer {
struct page *page;
unsigned int offset, len;
struct pipe_buf_operations *ops;
- unsigned int stolen;
+ unsigned int flags;
};
struct pipe_buf_operations {
@@ -63,5 +66,6 @@
#define SPLICE_F_NONBLOCK (0x02) /* don't block on the pipe splicing (but */
/* we may still block on the fd we splice */
/* from/to, of course */
+#define SPLICE_F_MORE (0x04) /* expect more data */
#endif
