fuse: update file size on short read

If the READ request returned a short count, then either

  - cached size is incorrect
  - filesystem is buggy, as short reads are only allowed on EOF

So assume that the size is wrong and refresh it, so that cached read() doesn't
zero fill the missing chunk.

Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 46 insertions, 6 deletions

diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index c5b5982bf38..a02418c89d4 100644
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -363,7 +363,7 @@ static int fuse_fsync(struct file *file, struct dentry *de, int datasync)
 void fuse_read_fill(struct fuse_req *req, struct file *file,
 		    struct inode *inode, loff_t pos, size_t count, int opcode)
 {
-	struct fuse_read_in *inarg = &req->misc.read_in;
+	struct fuse_read_in *inarg = &req->misc.read.in;
 	struct fuse_file *ff = file->private_data;
 
 	inarg->fh = ff->fh;
@@ -389,7 +389,7 @@ static size_t fuse_send_read(struct fuse_req *req, struct file *file,
 
 	fuse_read_fill(req, file, inode, pos, count, FUSE_READ);
 	if (owner != NULL) {
-		struct fuse_read_in *inarg = &req->misc.read_in;
+		struct fuse_read_in *inarg = &req->misc.read.in;
 
 		inarg->read_flags |= FUSE_READ_LOCKOWNER;
 		inarg->lock_owner = fuse_lock_owner_id(fc, owner);
@@ -398,11 +398,29 @@ static size_t fuse_send_read(struct fuse_req *req, struct file *file,
 	return req->out.args[0].size;
 }
 
+static void fuse_read_update_size(struct inode *inode, loff_t size,
+				  u64 attr_ver)
+{
+	struct fuse_conn *fc = get_fuse_conn(inode);
+	struct fuse_inode *fi = get_fuse_inode(inode);
+
+	spin_lock(&fc->lock);
+	if (attr_ver == fi->attr_version && size < inode->i_size) {
+		fi->attr_version = ++fc->attr_version;
+		i_size_write(inode, size);
+	}
+	spin_unlock(&fc->lock);
+}
+
 static int fuse_readpage(struct file *file, struct page *page)
 {
 	struct inode *inode = page->mapping->host;
 	struct fuse_conn *fc = get_fuse_conn(inode);
 	struct fuse_req *req;
+	size_t num_read;
+	loff_t pos = page_offset(page);
+	size_t count = PAGE_CACHE_SIZE;
+	u64 attr_ver;
 	int err;
 
 	err = -EIO;
@@ -421,15 +439,25 @@ static int fuse_readpage(struct file *file, struct page *page)
 	if (IS_ERR(req))
 		goto out;
 
+	attr_ver = fuse_get_attr_version(fc);
+
 	req->out.page_zeroing = 1;
 	req->num_pages = 1;
 	req->pages[0] = page;
-	fuse_send_read(req, file, inode, page_offset(page), PAGE_CACHE_SIZE,
-		       NULL);
+	num_read = fuse_send_read(req, file, inode, pos, count, NULL);
 	err = req->out.h.error;
 	fuse_put_request(fc, req);
-	if (!err)
+
+	if (!err) {
+		/*
+		 * Short read means EOF.  If file size is larger, truncate it
+		 */
+		if (num_read < count)
+			fuse_read_update_size(inode, pos + num_read, attr_ver);
+
 		SetPageUptodate(page);
+	}
+
 	fuse_invalidate_attr(inode); /* atime changed */
  out:
 	unlock_page(page);
@@ -439,8 +467,19 @@ static int fuse_readpage(struct file *file, struct page *page)
 static void fuse_readpages_end(struct fuse_conn *fc, struct fuse_req *req)
 {
 	int i;
+	size_t count = req->misc.read.in.size;
+	size_t num_read = req->out.args[0].size;
+	struct inode *inode = req->pages[0]->mapping->host;
 
-	fuse_invalidate_attr(req->pages[0]->mapping->host); /* atime changed */
+	/*
+	 * Short read means EOF.  If file size is larger, truncate it
+	 */
+	if (!req->out.h.error && num_read < count) {
+		loff_t pos = page_offset(req->pages[0]) + num_read;
+		fuse_read_update_size(inode, pos, req->misc.read.attr_ver);
+	}
+
+	fuse_invalidate_attr(inode); /* atime changed */
 
 	for (i = 0; i < req->num_pages; i++) {
 		struct page *page = req->pages[i];
@@ -463,6 +502,7 @@ static void fuse_send_readpages(struct fuse_req *req, struct file *file,
 	size_t count = req->num_pages << PAGE_CACHE_SHIFT;
 	req->out.page_zeroing = 1;
 	fuse_read_fill(req, file, inode, pos, count, FUSE_READ);
+	req->misc.read.attr_ver = fuse_get_attr_version(fc);
 	if (fc->async_read) {
 		struct fuse_file *ff = file->private_data;
 		req->ff = fuse_file_get(ff);