On Wed, Oct 23, 2019 at 09:25:23PM +0900, Misono Tomohiro wrote:
> When writeback mode is enabled (-o writeback), O_APPEND handling is
> done in kernel. Therefore virtiofsd clears O_APPEND flag when open.
> Otherwise O_APPEND flag takes precedence over pwrite() and write
> data may corrupt.
>
> Currently clearing O_APPEND flag is done in lo_open(), but we also
> need the same operation in lo_create(). So, factor out the flag
> update operation in lo_open() to update_open_flags() and call it
> in both lo_open() and lo_create().
>
> This fixes the failure of xfstest generic/069 in writeback mode
> (which tests O_APPEND write data integrity).
>
> Signed-off-by: Misono Tomohiro <misono.tomoh...@jp.fujitsu.com>
Reviewed-by: Vivek Goyal <vgo...@redhat.com>
Thanks
Vivek
> ---
> contrib/virtiofsd/passthrough_ll.c | 56 +++++++++++++++---------------
> 1 file changed, 28 insertions(+), 28 deletions(-)
>
> diff --git a/contrib/virtiofsd/passthrough_ll.c
> b/contrib/virtiofsd/passthrough_ll.c
> index e8892c3c32..79fb78ecce 100644
> --- a/contrib/virtiofsd/passthrough_ll.c
> +++ b/contrib/virtiofsd/passthrough_ll.c
> @@ -1733,6 +1733,32 @@ static void lo_releasedir(fuse_req_t req, fuse_ino_t
> ino, struct fuse_file_info
> fuse_reply_err(req, 0);
> }
>
> +static void update_open_flags(int writeback, struct fuse_file_info *fi)
> +{
> + /* With writeback cache, kernel may send read requests even
> + when userspace opened write-only */
> + if (writeback && (fi->flags & O_ACCMODE) == O_WRONLY) {
> + fi->flags &= ~O_ACCMODE;
> + fi->flags |= O_RDWR;
> + }
> +
> + /* With writeback cache, O_APPEND is handled by the kernel.
> + This breaks atomicity (since the file may change in the
> + underlying filesystem, so that the kernel's idea of the
> + end of the file isn't accurate anymore). In this example,
> + we just accept that. A more rigorous filesystem may want
> + to return an error here */
> + if (writeback && (fi->flags & O_APPEND))
> + fi->flags &= ~O_APPEND;
> +
> + /*
> + * O_DIRECT in guest should not necessarily mean bypassing page
> + * cache on host as well. If somebody needs that behavior, it
> + * probably should be a configuration knob in daemon.
> + */
> + fi->flags &= ~O_DIRECT;
> +}
> +
> static void lo_create(fuse_req_t req, fuse_ino_t parent, const char *name,
> mode_t mode, struct fuse_file_info *fi)
> {
> @@ -1760,12 +1786,7 @@ static void lo_create(fuse_req_t req, fuse_ino_t
> parent, const char *name,
> if (err)
> goto out;
>
> - /*
> - * O_DIRECT in guest should not necessarily mean bypassing page
> - * cache on host as well. If somebody needs that behavior, it
> - * probably should be a configuration knob in daemon.
> - */
> - fi->flags &= ~O_DIRECT;
> + update_open_flags(lo->writeback, fi);
>
> fd = openat(parent_inode->fd, name,
> (fi->flags | O_CREAT) & ~O_NOFOLLOW, mode);
> @@ -1966,28 +1987,7 @@ static void lo_open(fuse_req_t req, fuse_ino_t ino,
> struct fuse_file_info *fi)
>
> fuse_log(FUSE_LOG_DEBUG, "lo_open(ino=%" PRIu64 ", flags=%d)\n", ino,
> fi->flags);
>
> - /* With writeback cache, kernel may send read requests even
> - when userspace opened write-only */
> - if (lo->writeback && (fi->flags & O_ACCMODE) == O_WRONLY) {
> - fi->flags &= ~O_ACCMODE;
> - fi->flags |= O_RDWR;
> - }
> -
> - /* With writeback cache, O_APPEND is handled by the kernel.
> - This breaks atomicity (since the file may change in the
> - underlying filesystem, so that the kernel's idea of the
> - end of the file isn't accurate anymore). In this example,
> - we just accept that. A more rigorous filesystem may want
> - to return an error here */
> - if (lo->writeback && (fi->flags & O_APPEND))
> - fi->flags &= ~O_APPEND;
> -
> - /*
> - * O_DIRECT in guest should not necessarily mean bypassing page
> - * cache on host as well. If somebody needs that behavior, it
> - * probably should be a configuration knob in daemon.
> - */
> - fi->flags &= ~O_DIRECT;
> + update_open_flags(lo->writeback, fi);
>
> sprintf(buf, "%i", lo_fd(req, ino));
> fd = openat(lo->proc_self_fd, buf, fi->flags & ~O_NOFOLLOW);
> --
> 2.21.0
>
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