On Thu, Aug 21, 2014 at 6:09 PM, Maxim Patlasov <mpatla...@parallels.com> wrote:
> Synchronous release ensures that kernel fuse reports to userspace exactly
> last fput(). However, nothing guarantees that last fput() will happen in the
> context of close(2). So userspace applications must be prepared to the
> situation when close(2) returned, but processing of FUSE_RELEASE is not
> completed by fuse daemon yet. To make testing such use cases easier, the
> patch introduces DISABLE_SYNC_RELEASE mount option which effectively mask out
> FOPEN_SYNC_RELEASE flag.
Why not make this an INIT flag? Much easier to add support for in userspace.
Thanks,
Miklos
>
> Signed-off-by: Maxim Patlasov <mpatla...@parallels.com>
> ---
> ---
> fs/fuse/file.c | 3 ++-
> fs/fuse/fuse_i.h | 3 +++
> fs/fuse/inode.c | 8 ++++++++
> 3 files changed, 13 insertions(+), 1 deletion(-)
>
> diff --git a/fs/fuse/file.c b/fs/fuse/file.c
> index b92143a..ad3d357 100644
> --- a/fs/fuse/file.c
> +++ b/fs/fuse/file.c
> @@ -296,7 +296,8 @@ static void fuse_prepare_release(struct fuse_file *ff,
> int flags, int opcode)
>
> static bool must_release_synchronously(struct fuse_file *ff)
> {
> - return ff->open_flags & FOPEN_SYNC_RELEASE;
> + return ff->open_flags & FOPEN_SYNC_RELEASE &&
> + !(ff->fc->flags & FUSE_DISABLE_SYNC_RELEASE);
> }
>
> void fuse_release_common(struct file *file, int opcode)
> diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h
> index e8e47a6..c5e2fca 100644
> --- a/fs/fuse/fuse_i.h
> +++ b/fs/fuse/fuse_i.h
> @@ -44,6 +44,9 @@
> doing the mount will be allowed to access the filesystem */
> #define FUSE_ALLOW_OTHER (1 << 1)
>
> +/** Disable synchronous release */
> +#define FUSE_DISABLE_SYNC_RELEASE (1 << 2)
> +
> /** Number of page pointers embedded in fuse_req */
> #define FUSE_REQ_INLINE_PAGES 1
>
> diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
> index 03246cd..86d47d0 100644
> --- a/fs/fuse/inode.c
> +++ b/fs/fuse/inode.c
> @@ -463,6 +463,7 @@ enum {
> OPT_ALLOW_OTHER,
> OPT_MAX_READ,
> OPT_BLKSIZE,
> + OPT_DISABLE_SYNC_RELEASE,
> OPT_ERR
> };
>
> @@ -475,6 +476,7 @@ static const match_table_t tokens = {
> {OPT_ALLOW_OTHER, "allow_other"},
> {OPT_MAX_READ, "max_read=%u"},
> {OPT_BLKSIZE, "blksize=%u"},
> + {OPT_DISABLE_SYNC_RELEASE, "disable_sync_release"},
> {OPT_ERR, NULL}
> };
>
> @@ -560,6 +562,10 @@ static int parse_fuse_opt(char *opt, struct
> fuse_mount_data *d, int is_bdev)
> d->blksize = value;
> break;
>
> + case OPT_DISABLE_SYNC_RELEASE:
> + d->flags |= FUSE_DISABLE_SYNC_RELEASE;
> + break;
> +
> default:
> return 0;
> }
> @@ -583,6 +589,8 @@ static int fuse_show_options(struct seq_file *m, struct
> dentry *root)
> seq_puts(m, ",default_permissions");
> if (fc->flags & FUSE_ALLOW_OTHER)
> seq_puts(m, ",allow_other");
> + if (fc->flags & FUSE_DISABLE_SYNC_RELEASE)
> + seq_puts(m, ",disable_sync_release");
> if (fc->max_read != ~0)
> seq_printf(m, ",max_read=%u", fc->max_read);
> if (sb->s_bdev && sb->s_blocksize != FUSE_DEFAULT_BLKSIZE)
>
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