Hi Sjoerd,

On 05/11/2021 08:10, Sjoerd Simons wrote:

Hostfs was not setting up the backing device information, which means it uses the noop bdi. The noop bdi does not have the writeback capability enabled, which in turns means dirty pages never got written back to storage.

In other words programs using mmap to write to files on hostfs never actually got their data written out...

Fix this by simply setting up the bdi with default settings as all the required code for writeback is already in place.

Signed-off-by: Sjoerd Simons sjoerd@collabora.com

Cc: stable@vger.kernel.org Reviewed-by: Christopher Obbard chris.obbard@collabora.com

...replying mainly as I wonder if adding the stable tag in a reply will make the patch appear in stable (obviously once it is in mainline) ? :-)

---

fs/hostfs/hostfs_kern.c | 3 +++ 1 file changed, 3 insertions(+)

diff --git a/fs/hostfs/hostfs_kern.c b/fs/hostfs/hostfs_kern.c index d5c9d886cd9f..ef481c3d9019 100644 --- a/fs/hostfs/hostfs_kern.c +++ b/fs/hostfs/hostfs_kern.c @@ -924,6 +924,9 @@ static int hostfs_fill_sb_common(struct super_block *sb, void *d, int silent) sb->s_op = &hostfs_sbops; sb->s_d_op = &simple_dentry_operations; sb->s_maxbytes = MAX_LFS_FILESIZE;

• err = super_setup_bdi(sb);
• if (err)

• goto out;
  

/* NULL is printed as '(null)' by printf(): avoid that. */ if (req_root == NULL)