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document PUFFSFLAG_NOCACHE

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pooka 2006-11-17 18:00:20 +00:00
parent a2646bee20
commit 8bf1f71b17
1 changed files with 35 additions and 30 deletions
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65
share/man/man4/puffs.4
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@ -1,4 +1,4 @@
.\" $NetBSD: puffs.4,v 1.1 2006/11/09 01:29:34 pooka Exp $
.\" $NetBSD: puffs.4,v 1.2 2006/11/17 18:00:20 pooka Exp $
.\"
.\" Copyright (c) 2006 Antti Kantee. All rights reserved.
.\"
@ -23,7 +23,7 @@
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
.Dd November 8, 2006
.Dd November 17, 2006
.Dt PUFFS 4
.Os
.Sh NAME
@ -79,44 +79,51 @@ The
.Va pa_fd
member is the file descriptor number from opening the device node.
.Va pa_flags
controls some operations specific to puffs and currently can be 0
or
.Dv PUFFS_FLAG_ALLOWCTL
to allow file system fcntl and ioctl operations (these have security
implications).
controls some operations specific to puffs:
.Bl -tag -width "PUFFSFLAG_ALLOWCTL"
.It Dv PUFFSFLAG_ALLOWCTL
Allow file system fcntl and ioctl operations.
Allowing these has security implications as the file system can
technically read anything out of a calling processes address space.
This flag may additionally be enforced by the kernel security policy.
.It Dv PUFFSFLAG_NOCACHE
Do not store data in the page cache.
This causes operations to always consult the user server instead of
consulting the page cache.
This makes sense in situations where there is relatively little
bulk data to be transferred and the user server does not want to take
part in complex cache management routines in case the file system data
can be modified through routes other than the file system interface.
.El
.Pp
The
.Va pa_maxreqlen
member signifies the length of the incoming data buffer in userspace.
A good value is
.Dv PUFFS_REQ_MAXSIZE ,
which is the maximum the kernel will use.
A minimum value is also enforced, so the value of this field should
be checked after the mount operation to determine the correct buffer
size.
During operation, in case request fetch is attempted with a buffer
too short, the error
which is the maximum the kernel will use. A minimum value is also
enforced, so the value of this field should be checked after the
mount operation to determine the correct buffer size. During
operation, in case request fetch is attempted with a buffer too
short, the error
.Er E2BIG
will be returned.
.Pp
After a succesful mount system call, the the ioctl
.Dv PUFFSMOUNTOP
must be issued through the open device node.
The parameter for this ioctl is the following structure:
must be issued through the open device node. The parameter for
this ioctl is the following structure:
.Bd -literal -offset indent
struct puffs_startreq {
void *psr_cookie;
fsid_t psr_fsidx;
};
struct puffs_startreq {
void *psr_cookie; fsid_t psr_fsidx; };
.Ed
.Pp
The member
.Va psr_cookie
should be set before calling.
This signals the cookie value of the root node of the file system
(see
should be set before calling. This signals the cookie value of
the root node of the file system (see
.Xr puffs 3
for more details on cookie strategies).
The value of
for more details on cookie strategies). The value of
.Va psr_fsidx
will be filled by the kernel and should be recorded for future use.
After succesfully executing this operation the file system is
@ -131,8 +138,8 @@ Normally the system will block until an event is available for
but it is possible to set the file descriptor into non-blocking
mode, in which case
.Er EWOULDBLOCK
is returned if no event is available.
Asynchoronous I/O calls (i.e.
is returned if no event is available. Asynchoronous I/O calls
(i.e.
.Xr select 2 ,
.Xr poll 2 ,
and
@ -142,10 +149,8 @@ can be issued to be notified of events.
As the argument both get and push use the following structure:
.Bd -literal -offset indent
struct puffs_req {
uint64_t preq_id;
uint8_t preq_opclass;
uint8_t preq_optype;
void *preq_cookie;
uint64_t preq_id; uint8_t preq_opclass;
uint8_t preq_optype; void *preq_cookie;
int preq_rv;