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Message-ID: <20130629174535.20175.89175.stgit@maximpc.sw.ru>
Date: Sat, 29 Jun 2013 21:45:46 +0400
From: Maxim Patlasov <MPatlasov@...allels.com>
To: miklos@...redi.hu
Cc: riel@...hat.com, dev@...allels.com, xemul@...allels.com,
fuse-devel@...ts.sourceforge.net, bfoster@...hat.com,
linux-kernel@...r.kernel.org, jbottomley@...allels.com,
linux-mm@...ck.org, viro@...iv.linux.org.uk,
linux-fsdevel@...r.kernel.org, akpm@...ux-foundation.org,
fengguang.wu@...el.com, devel@...nvz.org, mgorman@...e.de
Subject: [PATCH 11/16] fuse: Implement write_begin/write_end callbacks
From: Pavel Emelyanov <xemul@...nvz.org>
The .write_begin and .write_end are requiered to use generic routines
(generic_file_aio_write --> ... --> generic_perform_write) for buffered
writes.
Signed-off-by: Maxim Patlasov <MPatlasov@...allels.com>
---
fs/fuse/file.c | 97 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
1 files changed, 97 insertions(+), 0 deletions(-)
diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index ad3bb8a..89b08d6 100644
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -1826,6 +1826,101 @@ out:
return err;
}
+/*
+ * Determine the number of bytes of data the page contains
+ */
+static inline unsigned fuse_page_length(struct page *page)
+{
+ loff_t i_size = i_size_read(page_file_mapping(page)->host);
+
+ if (i_size > 0) {
+ pgoff_t page_index = page_file_index(page);
+ pgoff_t end_index = (i_size - 1) >> PAGE_CACHE_SHIFT;
+ if (page_index < end_index)
+ return PAGE_CACHE_SIZE;
+ if (page_index == end_index)
+ return ((i_size - 1) & ~PAGE_CACHE_MASK) + 1;
+ }
+ return 0;
+}
+
+static int fuse_prepare_write(struct fuse_conn *fc, struct file *file,
+ struct page *page, loff_t pos, unsigned len)
+{
+ struct fuse_req *req = NULL;
+ unsigned num_read;
+ unsigned page_len;
+ int err;
+
+ if (PageUptodate(page) || (len == PAGE_CACHE_SIZE))
+ return 0;
+
+ page_len = fuse_page_length(page);
+ if (!page_len) {
+ zero_user(page, 0, PAGE_CACHE_SIZE);
+ return 0;
+ }
+
+ num_read = __fuse_readpage(file, page, page_len, &err, &req, NULL);
+ if (req)
+ fuse_put_request(fc, req);
+ if (err) {
+ unlock_page(page);
+ page_cache_release(page);
+ } else if (num_read != PAGE_CACHE_SIZE) {
+ zero_user_segment(page, num_read, PAGE_CACHE_SIZE);
+ }
+ return err;
+}
+
+/*
+ * It's worthy to make sure that space is reserved on disk for the write,
+ * but how to implement it without killing performance need more thinking.
+ */
+static int fuse_write_begin(struct file *file, struct address_space *mapping,
+ loff_t pos, unsigned len, unsigned flags,
+ struct page **pagep, void **fsdata)
+{
+ pgoff_t index = pos >> PAGE_CACHE_SHIFT;
+ struct fuse_conn *fc = get_fuse_conn(file->f_dentry->d_inode);
+
+ BUG_ON(!fc->writeback_cache);
+
+ *pagep = grab_cache_page_write_begin(mapping, index, flags);
+ if (!*pagep)
+ return -ENOMEM;
+
+ return fuse_prepare_write(fc, file, *pagep, pos, len);
+}
+
+static int fuse_commit_write(struct file *file, struct page *page,
+ unsigned from, unsigned to)
+{
+ struct inode *inode = page->mapping->host;
+ loff_t pos = ((loff_t)page->index << PAGE_CACHE_SHIFT) + to;
+
+ if (!PageUptodate(page))
+ SetPageUptodate(page);
+
+ fuse_write_update_size(inode, pos);
+ set_page_dirty(page);
+ return 0;
+}
+
+static int fuse_write_end(struct file *file, struct address_space *mapping,
+ loff_t pos, unsigned len, unsigned copied,
+ struct page *page, void *fsdata)
+{
+ unsigned from = pos & (PAGE_CACHE_SIZE - 1);
+
+ fuse_commit_write(file, page, from, from+copied);
+
+ unlock_page(page);
+ page_cache_release(page);
+
+ return copied;
+}
+
static int fuse_launder_page(struct page *page)
{
int err = 0;
@@ -2838,6 +2933,8 @@ static const struct address_space_operations fuse_file_aops = {
.set_page_dirty = __set_page_dirty_nobuffers,
.bmap = fuse_bmap,
.direct_IO = fuse_direct_IO,
+ .write_begin = fuse_write_begin,
+ .write_end = fuse_write_end,
};
void fuse_init_file_inode(struct inode *inode)
--
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