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Commit 3634a632 authored by Brian Foster's avatar Brian Foster Committed by Miklos Szeredi
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fuse: truncate pagecache range on hole punch 



fuse supports hole punch via the fallocate() FALLOC_FL_PUNCH_HOLE
interface. When a hole punch is passed through, the page cache
is not cleared and thus allows reading stale data from the cache.

This is easily demonstrable (using FOPEN_KEEP_CACHE) by reading a
smallish random data file into cache, punching a hole and creating
a copy of the file. Drop caches or remount and observe that the
original file no longer matches the file copied after the hole
punch. The original file contains a zeroed range and the latter
file contains stale data.

Protect against writepage requests in progress and punch out the
associated page cache range after a successful client fs hole
punch.

Signed-off-by: default avatarBrian Foster <bfoster@redhat.com>
Signed-off-by: default avatarMiklos Szeredi <mszeredi@suse.cz>
parent de82b923

fs/fuse/file.c

+20 −2
Original line number Diff line number Diff line
@@ -16,6 +16,7 @@ 
#include <linux/compat.h>

#include <linux/swap.h>

#include <linux/aio.h>

#include <linux/falloc.h>



static const struct file_operations fuse_direct_io_file_operations;
@@ -2453,6 +2454,7 @@ static long fuse_file_fallocate(struct file *file, int mode, loff_t offset, 
				loff_t length)

{

	struct fuse_file *ff = file->private_data;

	struct inode *inode = file->f_inode;

	struct fuse_conn *fc = ff->fc;

	struct fuse_req *req;

	struct fuse_fallocate_in inarg = {
@@ -2466,9 +2468,16 @@ static long fuse_file_fallocate(struct file *file, int mode, loff_t offset, 
	if (fc->no_fallocate)

		return -EOPNOTSUPP;



	if (mode & FALLOC_FL_PUNCH_HOLE) {

		mutex_lock(&inode->i_mutex);

		fuse_set_nowrite(inode);

	}



	req = fuse_get_req_nopages(fc);

	if (IS_ERR(req))

		return PTR_ERR(req);

	if (IS_ERR(req)) {

		err = PTR_ERR(req);

		goto out;

	}



	req->in.h.opcode = FUSE_FALLOCATE;

	req->in.h.nodeid = ff->nodeid;
@@ -2483,6 +2492,15 @@ static long fuse_file_fallocate(struct file *file, int mode, loff_t offset, 
	}

	fuse_put_request(fc, req);



out:

	if (mode & FALLOC_FL_PUNCH_HOLE) {

		if (!err)

			truncate_pagecache_range(inode, offset,

						 offset + length - 1);

		fuse_release_nowrite(inode);

		mutex_unlock(&inode->i_mutex);

	}



	return err;

}