* [PATCH] virtiofsd: Do not support blocking flock
@ 2022-01-11 18:10 ` Sebastian Hasler
0 siblings, 0 replies; 5+ messages in thread
From: Sebastian Hasler @ 2022-01-11 18:10 UTC (permalink / raw)
To: qemu-devel; +Cc: virtio-fs, Sebastian Hasler
With the current implementation, blocking flock can lead to
deadlock. Thus, it's better to return EOPNOTSUPP if a user attempts
to perform a blocking flock request.
Signed-off-by: Sebastian Hasler <sebastian.hasler@stuvus.uni-stuttgart.de>
---
tools/virtiofsd/passthrough_ll.c | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/tools/virtiofsd/passthrough_ll.c b/tools/virtiofsd/passthrough_ll.c
index 64b5b4fbb1..f3cc307f6d 100644
--- a/tools/virtiofsd/passthrough_ll.c
+++ b/tools/virtiofsd/passthrough_ll.c
@@ -2442,6 +2442,12 @@ static void lo_flock(fuse_req_t req, fuse_ino_t ino, struct fuse_file_info *fi,
int res;
(void)ino;
+ if (!(op & LOCK_NB)) {
+ /* Blocking flock is not supported */
+ fuse_reply_err(req, EOPNOTSUPP);
+ return;
+ }
+
res = flock(lo_fi_fd(req, fi), op);
fuse_reply_err(req, res == -1 ? errno : 0);
--
2.33.1
^ permalink raw reply related [flat|nested] 5+ messages in thread
* [Virtio-fs] [PATCH] virtiofsd: Do not support blocking flock
@ 2022-01-11 18:10 ` Sebastian Hasler
0 siblings, 0 replies; 5+ messages in thread
From: Sebastian Hasler @ 2022-01-11 18:10 UTC (permalink / raw)
To: qemu-devel; +Cc: virtio-fs, Sebastian Hasler
With the current implementation, blocking flock can lead to
deadlock. Thus, it's better to return EOPNOTSUPP if a user attempts
to perform a blocking flock request.
Signed-off-by: Sebastian Hasler <sebastian.hasler@stuvus.uni-stuttgart.de>
---
tools/virtiofsd/passthrough_ll.c | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/tools/virtiofsd/passthrough_ll.c b/tools/virtiofsd/passthrough_ll.c
index 64b5b4fbb1..f3cc307f6d 100644
--- a/tools/virtiofsd/passthrough_ll.c
+++ b/tools/virtiofsd/passthrough_ll.c
@@ -2442,6 +2442,12 @@ static void lo_flock(fuse_req_t req, fuse_ino_t ino, struct fuse_file_info *fi,
int res;
(void)ino;
+ if (!(op & LOCK_NB)) {
+ /* Blocking flock is not supported */
+ fuse_reply_err(req, EOPNOTSUPP);
+ return;
+ }
+
res = flock(lo_fi_fd(req, fi), op);
fuse_reply_err(req, res == -1 ? errno : 0);
--
2.33.1
^ permalink raw reply related [flat|nested] 5+ messages in thread
* Re: [PATCH] virtiofsd: Do not support blocking flock
2022-01-11 18:10 ` [Virtio-fs] " Sebastian Hasler
@ 2022-01-12 17:18 ` Sebastian Hasler
-1 siblings, 0 replies; 5+ messages in thread
From: Sebastian Hasler @ 2022-01-12 17:18 UTC (permalink / raw)
To: qemu-devel; +Cc: virtio-fs
On 11/01/2022 19:10, Sebastian Hasler wrote:
> With the current implementation, blocking flock can lead to
> deadlock. Thus, it's better to return EOPNOTSUPP if a user attempts
> to perform a blocking flock request.
>
> Signed-off-by: Sebastian Hasler <sebastian.hasler@stuvus.uni-stuttgart.de>
> ---
> tools/virtiofsd/passthrough_ll.c | 6 ++++++
> 1 file changed, 6 insertions(+)
>
> diff --git a/tools/virtiofsd/passthrough_ll.c b/tools/virtiofsd/passthrough_ll.c
> index 64b5b4fbb1..f3cc307f6d 100644
> --- a/tools/virtiofsd/passthrough_ll.c
> +++ b/tools/virtiofsd/passthrough_ll.c
> @@ -2442,6 +2442,12 @@ static void lo_flock(fuse_req_t req, fuse_ino_t ino, struct fuse_file_info *fi,
> int res;
> (void)ino;
>
> + if (!(op & LOCK_NB)) {
> + /* Blocking flock is not supported */
> + fuse_reply_err(req, EOPNOTSUPP);
> + return;
> + }
> +
> res = flock(lo_fi_fd(req, fi), op);
>
> fuse_reply_err(req, res == -1 ? errno : 0);
I tested this patch by cherry-picking it on v6.1.0 and using it with
Kata Containers 2.3.0. The bash code
exec 42>/lock/flock
flock -w 120 42
outputs
flock: 42: Operation not supported
while the bash code
exec 42>/lock/flock
flock --nonblock 42
still works. So it works as intended.
--
Sebastian Hasler
stuvus – Studierendenvertretung Universität Stuttgart
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [Virtio-fs] [PATCH] virtiofsd: Do not support blocking flock
@ 2022-01-12 17:18 ` Sebastian Hasler
0 siblings, 0 replies; 5+ messages in thread
From: Sebastian Hasler @ 2022-01-12 17:18 UTC (permalink / raw)
To: qemu-devel; +Cc: virtio-fs
On 11/01/2022 19:10, Sebastian Hasler wrote:
> With the current implementation, blocking flock can lead to
> deadlock. Thus, it's better to return EOPNOTSUPP if a user attempts
> to perform a blocking flock request.
>
> Signed-off-by: Sebastian Hasler <sebastian.hasler@stuvus.uni-stuttgart.de>
> ---
> tools/virtiofsd/passthrough_ll.c | 6 ++++++
> 1 file changed, 6 insertions(+)
>
> diff --git a/tools/virtiofsd/passthrough_ll.c b/tools/virtiofsd/passthrough_ll.c
> index 64b5b4fbb1..f3cc307f6d 100644
> --- a/tools/virtiofsd/passthrough_ll.c
> +++ b/tools/virtiofsd/passthrough_ll.c
> @@ -2442,6 +2442,12 @@ static void lo_flock(fuse_req_t req, fuse_ino_t ino, struct fuse_file_info *fi,
> int res;
> (void)ino;
>
> + if (!(op & LOCK_NB)) {
> + /* Blocking flock is not supported */
> + fuse_reply_err(req, EOPNOTSUPP);
> + return;
> + }
> +
> res = flock(lo_fi_fd(req, fi), op);
>
> fuse_reply_err(req, res == -1 ? errno : 0);
I tested this patch by cherry-picking it on v6.1.0 and using it with
Kata Containers 2.3.0. The bash code
exec 42>/lock/flock
flock -w 120 42
outputs
flock: 42: Operation not supported
while the bash code
exec 42>/lock/flock
flock --nonblock 42
still works. So it works as intended.
--
Sebastian Hasler
stuvus – Studierendenvertretung Universität Stuttgart
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [Virtio-fs] [PATCH] virtiofsd: Do not support blocking flock
2022-01-11 18:10 ` [Virtio-fs] " Sebastian Hasler
(?)
(?)
@ 2022-01-13 9:59 ` Greg Kurz
-1 siblings, 0 replies; 5+ messages in thread
From: Greg Kurz @ 2022-01-13 9:59 UTC (permalink / raw)
To: Sebastian Hasler; +Cc: virtio-fs, qemu-devel
On Tue, 11 Jan 2022 19:10:43 +0100
Sebastian Hasler <sebastian.hasler@stuvus.uni-stuttgart.de> wrote:
> With the current implementation, blocking flock can lead to
> deadlock. Thus, it's better to return EOPNOTSUPP if a user attempts
> to perform a blocking flock request.
>
> Signed-off-by: Sebastian Hasler <sebastian.hasler@stuvus.uni-stuttgart.de>
> ---
> tools/virtiofsd/passthrough_ll.c | 6 ++++++
> 1 file changed, 6 insertions(+)
>
> diff --git a/tools/virtiofsd/passthrough_ll.c b/tools/virtiofsd/passthrough_ll.c
> index 64b5b4fbb1..f3cc307f6d 100644
> --- a/tools/virtiofsd/passthrough_ll.c
> +++ b/tools/virtiofsd/passthrough_ll.c
> @@ -2442,6 +2442,12 @@ static void lo_flock(fuse_req_t req, fuse_ino_t ino, struct fuse_file_info *fi,
> int res;
> (void)ino;
>
> + if (!(op & LOCK_NB)) {
> + /* Blocking flock is not supported */
This paraphrases the code. It would be more informative to provide
an explanation, something like /* Blocking flock can deadlock */ .
No big deal.
Reviewed-by: Greg Kurz <groug@kaod.org>
> + fuse_reply_err(req, EOPNOTSUPP);
> + return;
> + }
> +
> res = flock(lo_fi_fd(req, fi), op);
>
> fuse_reply_err(req, res == -1 ? errno : 0);
^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2022-01-13 9:59 UTC | newest]
Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed)
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2022-01-11 18:10 [PATCH] virtiofsd: Do not support blocking flock Sebastian Hasler
2022-01-11 18:10 ` [Virtio-fs] " Sebastian Hasler
2022-01-12 17:18 ` Sebastian Hasler
2022-01-12 17:18 ` [Virtio-fs] " Sebastian Hasler
2022-01-13 9:59 ` Greg Kurz
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