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fuse: Implement writepages callback 

The .writepages one is required to make each writeback request carry more than
one page on it. The patch enables optimized behaviour unconditionally,
i.e. mmap-ed writes will benefit from the patch even if fc->writeback_cache=0.

[SzM: simplify, add comments]

Signed-off-by: Maxim Patlasov <MPatlasov@parallels.com>
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
This commit is contained in:
Pavel Emelyanov 2013-06-29 21:45:29 +04:00 committed by Miklos Szeredi
parent 72523425fb
commit 26d614df1d
1 changed files with 147 additions and 3 deletions
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150
fs/fuse/file.c
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@ -1502,8 +1502,8 @@ static void fuse_writepage_end(struct fuse_conn *fc, struct fuse_req *req)
fuse_writepage_free(fc, req);
}
static struct fuse_file *fuse_write_file(struct fuse_conn *fc,
struct fuse_inode *fi)
static struct fuse_file *fuse_write_file_get(struct fuse_conn *fc,
struct fuse_inode *fi)
{
struct fuse_file *ff = NULL;
@ -1540,7 +1540,7 @@ static int fuse_writepage_locked(struct page *page)
goto err_free;
error = -EIO;
req->ff = fuse_write_file(fc, fi);
req->ff = fuse_write_file_get(fc, fi);
if (!req->ff)
goto err_free;
@ -1586,6 +1586,149 @@ static int fuse_writepage(struct page *page, struct writeback_control *wbc)
return err;
}
struct fuse_fill_wb_data {
struct fuse_req *req;
struct fuse_file *ff;
struct inode *inode;
};
static void fuse_writepages_send(struct fuse_fill_wb_data *data)
{
struct fuse_req *req = data->req;
struct inode *inode = data->inode;
struct fuse_conn *fc = get_fuse_conn(inode);
struct fuse_inode *fi = get_fuse_inode(inode);
req->ff = fuse_file_get(data->ff);
spin_lock(&fc->lock);
list_add_tail(&req->list, &fi->queued_writes);
fuse_flush_writepages(inode);
spin_unlock(&fc->lock);
}
static int fuse_writepages_fill(struct page *page,
struct writeback_control *wbc, void *_data)
{
struct fuse_fill_wb_data *data = _data;
struct fuse_req *req = data->req;
struct inode *inode = data->inode;
struct fuse_conn *fc = get_fuse_conn(inode);
struct page *tmp_page;
int err;
if (!data->ff) {
err = -EIO;
data->ff = fuse_write_file_get(fc, get_fuse_inode(inode));
if (!data->ff)
goto out_unlock;
}
if (req) {
BUG_ON(!req->num_pages);
if (req->num_pages == FUSE_MAX_PAGES_PER_REQ ||
(req->num_pages + 1) * PAGE_CACHE_SIZE > fc->max_write ||
req->pages[req->num_pages - 1]->index + 1 != page->index) {
fuse_writepages_send(data);
data->req = NULL;
}
}
err = -ENOMEM;
tmp_page = alloc_page(GFP_NOFS | __GFP_HIGHMEM);
if (!tmp_page)
goto out_unlock;
/*
* The page must not be redirtied until the writeout is completed
* (i.e. userspace has sent a reply to the write request). Otherwise
* there could be more than one temporary page instance for each real
* page.
*
* This is ensured by holding the page lock in page_mkwrite() while
* checking fuse_page_is_writeback(). We already hold the page lock
* since clear_page_dirty_for_io() and keep it held until we add the
* request to the fi->writepages list and increment req->num_pages.
* After this fuse_page_is_writeback() will indicate that the page is
* under writeback, so we can release the page lock.
*/
if (data->req == NULL) {
struct fuse_inode *fi = get_fuse_inode(inode);
err = -ENOMEM;
req = fuse_request_alloc_nofs(FUSE_MAX_PAGES_PER_REQ);
if (!req) {
__free_page(tmp_page);
goto out_unlock;
}
fuse_write_fill(req, data->ff, page_offset(page), 0);
req->misc.write.in.write_flags |= FUSE_WRITE_CACHE;
req->in.argpages = 1;
req->background = 1;
req->num_pages = 0;
req->end = fuse_writepage_end;
req->inode = inode;
spin_lock(&fc->lock);
list_add(&req->writepages_entry, &fi->writepages);
spin_unlock(&fc->lock);
data->req = req;
}
set_page_writeback(page);
copy_highpage(tmp_page, page);
req->pages[req->num_pages] = tmp_page;
req->page_descs[req->num_pages].offset = 0;
req->page_descs[req->num_pages].length = PAGE_SIZE;
inc_bdi_stat(page->mapping->backing_dev_info, BDI_WRITEBACK);
inc_zone_page_state(tmp_page, NR_WRITEBACK_TEMP);
end_page_writeback(page);
/*
* Protected by fc->lock against concurrent access by
* fuse_page_is_writeback().
*/
spin_lock(&fc->lock);
req->num_pages++;
spin_unlock(&fc->lock);
err = 0;
out_unlock:
unlock_page(page);
return err;
}
static int fuse_writepages(struct address_space *mapping,
struct writeback_control *wbc)
{
struct inode *inode = mapping->host;
struct fuse_fill_wb_data data;
int err;
err = -EIO;
if (is_bad_inode(inode))
goto out;
data.inode = inode;
data.req = NULL;
data.ff = NULL;
err = write_cache_pages(mapping, wbc, fuse_writepages_fill, &data);
if (data.req) {
/* Ignore errors if we can write at least one page */
BUG_ON(!data.req->num_pages);
fuse_writepages_send(&data);
err = 0;
}
if (data.ff)
fuse_file_put(data.ff, false);
out:
return err;
}
static int fuse_launder_page(struct page *page)
{
int err = 0;
@ -2607,6 +2750,7 @@ static const struct file_operations fuse_direct_io_file_operations = {
static const struct address_space_operations fuse_file_aops = {
.readpage = fuse_readpage,
.writepage = fuse_writepage,
.writepages = fuse_writepages,
.launder_page = fuse_launder_page,
.readpages = fuse_readpages,
.set_page_dirty = __set_page_dirty_nobuffers,