Commit 8373200b authored by Pavel Emelyanov's avatar Pavel Emelyanov Committed by Miklos Szeredi
Browse files

fuse: Trust kernel i_size only 



Make fuse think that when writeback is on the inode's i_size is always
up-to-date and not update it with the value received from the userspace.
This is done because the page cache code may update i_size without letting
the FS know.

This assumption implies fixing the previously introduced short-read helper --
when a short read occurs the 'hole' is filled with zeroes.

fuse_file_fallocate() is also fixed because now we should keep i_size up to
date, so it must be updated if FUSE_FALLOCATE request succeeded.

Signed-off-by: default avatarMaxim V. Patlasov <MPatlasov@parallels.com>
Signed-off-by: default avatarMiklos Szeredi <mszeredi@suse.cz>
parent d5cd66c5

fs/fuse/dir.c

+11 −2
Original line number Diff line number Diff line
@@ -839,6 +839,11 @@ static void fuse_fillattr(struct inode *inode, struct fuse_attr *attr, 
			  struct kstat *stat)

{

	unsigned int blkbits;

	struct fuse_conn *fc = get_fuse_conn(inode);



	/* see the comment in fuse_change_attributes() */

	if (fc->writeback_cache && S_ISREG(inode->i_mode))

		attr->size = i_size_read(inode);



	stat->dev = inode->i_sb->s_dev;

	stat->ino = attr->ino;
@@ -1580,6 +1585,7 @@ int fuse_do_setattr(struct inode *inode, struct iattr *attr, 
	struct fuse_setattr_in inarg;

	struct fuse_attr_out outarg;

	bool is_truncate = false;

	bool is_wb = fc->writeback_cache;

	loff_t oldsize;

	int err;
@@ -1651,6 +1657,8 @@ int fuse_do_setattr(struct inode *inode, struct iattr *attr, 
	fuse_change_attributes_common(inode, &outarg.attr,

				      attr_timeout(&outarg));

	oldsize = inode->i_size;

	/* see the comment in fuse_change_attributes() */

	if (!is_wb || is_truncate || !S_ISREG(inode->i_mode))

		i_size_write(inode, outarg.attr.size);



	if (is_truncate) {
@@ -1663,7 +1671,8 @@ int fuse_do_setattr(struct inode *inode, struct iattr *attr, 
	 * Only call invalidate_inode_pages2() after removing

	 * FUSE_NOWRITE, otherwise fuse_launder_page() would deadlock.

	 */

	if (S_ISREG(inode->i_mode) && oldsize != outarg.attr.size) {

	if ((is_truncate || !is_wb) &&

	    S_ISREG(inode->i_mode) && oldsize != outarg.attr.size) {

		truncate_pagecache(inode, outarg.attr.size);

		invalidate_inode_pages2(inode->i_mapping);

	}

fs/fuse/file.c

+19 −2
Original line number Diff line number Diff line
@@ -675,10 +675,27 @@ static void fuse_short_read(struct fuse_req *req, struct inode *inode, 
			    u64 attr_ver)

{

	size_t num_read = req->out.args[0].size;

	struct fuse_conn *fc = get_fuse_conn(inode);



	if (fc->writeback_cache) {

		/*

		 * A hole in a file. Some data after the hole are in page cache,

		 * but have not reached the client fs yet. So, the hole is not

		 * present there.

		 */

		int i;

		int start_idx = num_read >> PAGE_CACHE_SHIFT;

		size_t off = num_read & (PAGE_CACHE_SIZE - 1);



		for (i = start_idx; i < req->num_pages; i++) {

			zero_user_segment(req->pages[i], off, PAGE_CACHE_SIZE);

			off = 0;

		}

	} else {

		loff_t pos = page_offset(req->pages[0]) + num_read;

		fuse_read_update_size(inode, pos, attr_ver);

	}

}



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

{

fs/fuse/inode.c

+9 −2
Original line number Diff line number Diff line
@@ -197,6 +197,7 @@ void fuse_change_attributes(struct inode *inode, struct fuse_attr *attr, 
{

	struct fuse_conn *fc = get_fuse_conn(inode);

	struct fuse_inode *fi = get_fuse_inode(inode);

	bool is_wb = fc->writeback_cache;

	loff_t oldsize;

	struct timespec old_mtime;
@@ -211,10 +212,16 @@ void fuse_change_attributes(struct inode *inode, struct fuse_attr *attr, 
	fuse_change_attributes_common(inode, attr, attr_valid);



	oldsize = inode->i_size;

	/*

	 * In case of writeback_cache enabled, the cached writes beyond EOF

	 * extend local i_size without keeping userspace server in sync. So,

	 * attr->size coming from server can be stale. We cannot trust it.

	 */

	if (!is_wb || !S_ISREG(inode->i_mode))

		i_size_write(inode, attr->size);

	spin_unlock(&fc->lock);



	if (S_ISREG(inode->i_mode)) {

	if (!is_wb && S_ISREG(inode->i_mode)) {

		bool inval = false;



		if (oldsize != attr->size) {

CRA Git | Maintained and supported by SUSTech CRA and CCSE