Commit ae976416 authored by Hugh Dickins's avatar Hugh Dickins Committed by Jens Axboe
Browse files

shmem: convert to using splice instead of sendfile() 



Remove shmem_file_sendfile and resurrect shmem_readpage, as used by tmpfs
to support loop and sendfile in 2.4 and 2.5.  Now tmpfs can support splice,
loop and sendfile in the simplest way, using generic_file_splice_read and
generic_file_splice_write (with the aid of shmem_prepare_write).

We could make some efficiency tweaks later, if there's a real need;
but this is stable and works well as is.

Signed-off-by: default avatarHugh Dickins <hugh@veritas.com>
Signed-off-by: default avatarJens Axboe <jens.axboe@oracle.com>
parent 1db60cf2

mm/shmem.c

+17 −25
Original line number Diff line number Diff line
@@ -1100,9 +1100,9 @@ static int shmem_getpage(struct inode *inode, unsigned long idx, 
	 * Normally, filepage is NULL on entry, and either found

	 * uptodate immediately, or allocated and zeroed, or read

	 * in under swappage, which is then assigned to filepage.

	 * But shmem_prepare_write passes in a locked filepage,

	 * which may be found not uptodate by other callers too,

	 * and may need to be copied from the swappage read in.

	 * But shmem_readpage and shmem_prepare_write pass in a locked

	 * filepage, which may be found not uptodate by other callers

	 * too, and may need to be copied from the swappage read in.

	 */

repeat:

	if (!filepage)
@@ -1485,9 +1485,18 @@ static const struct inode_operations shmem_symlink_inode_operations; 
static const struct inode_operations shmem_symlink_inline_operations;



/*

 * Normally tmpfs makes no use of shmem_prepare_write, but it

 * lets a tmpfs file be used read-write below the loop driver.

 * Normally tmpfs avoids the use of shmem_readpage and shmem_prepare_write;

 * but providing them allows a tmpfs file to be used for splice, sendfile, and

 * below the loop driver, in the generic fashion that many filesystems support.

 */

static int shmem_readpage(struct file *file, struct page *page)

{

	struct inode *inode = page->mapping->host;

	int error = shmem_getpage(inode, page->index, &page, SGP_CACHE, NULL);

	unlock_page(page);

	return error;

}



static int

shmem_prepare_write(struct file *file, struct page *page, unsigned offset, unsigned to)

{
@@ -1711,25 +1720,6 @@ static ssize_t shmem_file_read(struct file *filp, char __user *buf, size_t count 
	return desc.error;

}



static ssize_t shmem_file_sendfile(struct file *in_file, loff_t *ppos,

			 size_t count, read_actor_t actor, void *target)

{

	read_descriptor_t desc;



	if (!count)

		return 0;



	desc.written = 0;

	desc.count = count;

	desc.arg.data = target;

	desc.error = 0;



	do_shmem_file_read(in_file, ppos, &desc, actor);

	if (desc.written)

		return desc.written;

	return desc.error;

}



static int shmem_statfs(struct dentry *dentry, struct kstatfs *buf)

{

	struct shmem_sb_info *sbinfo = SHMEM_SB(dentry->d_sb);
@@ -2386,6 +2376,7 @@ static const struct address_space_operations shmem_aops = { 
	.writepage	= shmem_writepage,

	.set_page_dirty	= __set_page_dirty_no_writeback,

#ifdef CONFIG_TMPFS

	.readpage	= shmem_readpage,

	.prepare_write	= shmem_prepare_write,

	.commit_write	= simple_commit_write,

#endif
@@ -2399,7 +2390,8 @@ static const struct file_operations shmem_file_operations = { 
	.read		= shmem_file_read,

	.write		= shmem_file_write,

	.fsync		= simple_sync_file,

	.sendfile	= shmem_file_sendfile,

	.splice_read	= generic_file_splice_read,

	.splice_write	= generic_file_splice_write,

#endif

};

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