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Merge branch 'splice' of git://brick.kernel.dk/data/git/linux-2.6-block
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* '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
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Linus Torvalds committed Apr 2, 2006
2 parents 1810b6c + 3e7ee3e commit d696361
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Showing 3 changed files with 146 additions and 41 deletions.
4 changes: 3 additions & 1 deletion fs/pipe.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -95,6 +95,8 @@ static void anon_pipe_buf_release(struct pipe_inode_info *info, struct pipe_buff
{
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
Expand Down Expand Up @@ -124,7 +126,7 @@ static void anon_pipe_buf_unmap(struct pipe_inode_info *info, struct pipe_buffer
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;
}

Expand Down
177 changes: 138 additions & 39 deletions fs/splice.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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
Expand All @@ -34,28 +37,37 @@ struct splice_desc {
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))
return 1;
/*
* 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 (PageLRU(page)) {
struct zone *zone = page_zone(page);
if (PagePrivate(page))
try_to_release_page(page, mapping_gfp_mask(mapping));

spin_lock_irq(&zone->lru_lock);
BUG_ON(!PageLRU(page));
__ClearPageLRU(page);
del_page_from_lru(zone, page);
spin_unlock_irq(&zone->lru_lock);
}
if (!remove_mapping(mapping, page))
return 1;

buf->stolen = 1;
buf->flags |= PIPE_BUF_FLAG_STOLEN | PIPE_BUF_FLAG_LRU;
return 0;
}

Expand All @@ -64,7 +76,7 @@ static void page_cache_pipe_buf_release(struct pipe_inode_info *info,
{
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,
Expand All @@ -91,8 +103,7 @@ static void *page_cache_pipe_buf_map(struct file *file,
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);
}

Expand All @@ -104,6 +115,10 @@ static struct pipe_buf_operations page_cache_pipe_buf_ops = {
.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)
Expand Down Expand Up @@ -237,9 +252,9 @@ static int __generic_file_splice_read(struct file *in, struct inode *pipe,
* 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
Expand Down Expand Up @@ -288,6 +303,16 @@ static int __generic_file_splice_read(struct file *in, struct inode *pipe,
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)
{
Expand Down Expand Up @@ -318,8 +343,11 @@ ssize_t generic_file_splice_read(struct file *in, struct inode *pipe,
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)
Expand All @@ -329,6 +357,7 @@ static int pipe_to_sendpage(struct pipe_inode_info *info,
unsigned int offset;
ssize_t ret;
void *ptr;
int more;

/*
* sub-optimal, but we are limited by the pipe ->map. we don't
Expand All @@ -341,9 +370,9 @@ static int pipe_to_sendpage(struct pipe_inode_info *info,
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)
Expand All @@ -365,16 +394,19 @@ static int pipe_to_sendpage(struct pipe_inode_info *info,
* - 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;
Expand All @@ -395,18 +427,23 @@ static int pipe_to_file(struct pipe_inode_info *info, struct pipe_buffer *buf,
* 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;

Expand Down Expand Up @@ -443,10 +480,13 @@ static int pipe_to_file(struct pipe_inode_info *info, struct pipe_buffer *buf,
}

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);
Expand All @@ -455,23 +495,30 @@ static int pipe_to_file(struct pipe_inode_info *info, struct pipe_buffer *buf,
}

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;
}

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)
Expand Down Expand Up @@ -573,21 +620,67 @@ static ssize_t move_from_pipe(struct inode *inode, struct file *out,

}

/**
* 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)
{
Expand All @@ -608,6 +701,9 @@ static long do_splice_from(struct inode *pipe, struct file *out, size_t len,
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)
{
Expand Down Expand Up @@ -636,6 +732,9 @@ static long do_splice_to(struct file *in, struct inode *pipe, size_t len,
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)
{
Expand Down
6 changes: 5 additions & 1 deletion include/linux/pipe_fs_i.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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 {
Expand Down Expand Up @@ -63,5 +66,6 @@ void free_pipe_info(struct inode* inode);
#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

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