fuse: truncate pagecache range on hole punch (3634a632) · Commits · 戴 / test

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:

Brian Foster <bfoster@redhat.com> Signed-off-by:

Miklos Szeredi <mszeredi@suse.cz>

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;
		}

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