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diff --git a/share/man/man9/g_bio.9 b/share/man/man9/g_bio.9 new file mode 100644 index 000000000000..e7351b8054e4 --- /dev/null +++ b/share/man/man9/g_bio.9 @@ -0,0 +1,277 @@ +.\" +.\" Copyright (c) 2004-2006 Pawel Jakub Dawidek <pjd@FreeBSD.org> +.\" All rights reserved. +.\" +.\" Redistribution and use in source and binary forms, with or without +.\" modification, are permitted provided that the following conditions +.\" are met: +.\" 1. Redistributions of source code must retain the above copyright +.\" notice, this list of conditions and the following disclaimer. +.\" 2. Redistributions in binary form must reproduce the above copyright +.\" notice, this list of conditions and the following disclaimer in the +.\" documentation and/or other materials provided with the distribution. +.\" +.\" THIS SOFTWARE IS PROVIDED BY THE DEVELOPERS ``AS IS'' AND ANY EXPRESS OR +.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES +.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. +.\" IN NO EVENT SHALL THE DEVELOPERS BE LIABLE FOR ANY DIRECT, INDIRECT, +.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT +.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, +.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY +.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT +.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF +.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. +.\" +.\" $FreeBSD$ +.\" +.Dd November 1, 2006 +.Dt G_BIO 9 +.Os +.Sh NAME +.Nm g_new_bio , +.Nm g_clone_bio , +.Nm g_destroy_bio , +.Nm g_print_bio +.Nd "GEOM bio controlling functions" +.Sh SYNOPSIS +.In sys/bio.h +.In geom/geom.h +.Ft "struct bio *" +.Fn g_new_bio void +.Ft "struct bio *" +.Fn g_alloc_bio void +.Ft "struct bio *" +.Fn g_clone_bio "struct bio *bp" +.Ft "struct bio *" +.Fn g_duplicate_bio "struct bio *bp" +.Ft void +.Fn g_destroy_bio "struct bio *bp" +.Ft void +.Fn g_print_bio "struct bio *bp" +.Sh DESCRIPTION +A +.Vt "struct bio" +is used by GEOM to describe I/O requests, its +most important fields are described below: +.Bl -tag -width ".Va bio_attribute" +.It Va bio_cmd +I/O request command. +There are four I/O requests available in GEOM: +.Bl -tag -width ".Dv BIO_GETATTR" +.It Dv BIO_READ +A read request. +.It Dv BIO_WRITE +A write request. +.It Dv BIO_DELETE +Indicates that a certain range of data is no longer used and that +it can be erased or freed as the underlying technology supports. +Technologies like flash adaptation layers can arrange to erase the relevant +blocks before they will become reassigned and cryptographic devices may +want to fill random bits into the range to reduce the amount of data +available for attack. +.It Dv BIO_GETATTR +Inspect and manipulate out-of-band +attributes on a particular provider or path. +Attributes are named by ascii strings and are stored in the +.Va bio_attribute +field. +.It Dv BIO_FLUSH +Tells underlying providers to flush their write caches. +.El +.It Va bio_flags +Available flags: +.Bl -tag -width ".Dv BIO_ERROR" +.It Dv BIO_ERROR +Request failed (error value is stored in +.Va bio_error +field). +.It Dv BIO_DONE +Request finished. +.El +.It Va bio_cflags +Private use by the consumer. +.It Va bio_pflags +Private use by the provider. +.It Va bio_offset +Offset into provider. +.It Va bio_data +Pointer to data buffer. +.It Va bio_error +Error value when +.Dv BIO_ERROR +is set. +.It Va bio_done +Pointer to function which will be called when the request is finished. +.It Va bio_driver1 +Private use by the provider. +.It Va bio_driver2 +Private use by the provider. +.It Va bio_caller1 +Private use by the consumer. +.It Va bio_caller2 +Private use by the consumer. +.It Va bio_attribute +Attribute string for +.Dv BIO_GETATTR +request. +.It Va bio_from +Consumer to use for request (attached to provider stored in +.Va bio_to +field) (typically read-only for a class). +.It Va bio_to +Destination provider (typically read-only for a class). +.It Va bio_length +Request length in bytes. +.It Va bio_completed +Number of bytes completed, but they may not be completed from +the front of the request. +.It Va bio_children +Number of +.Vt bio +clones (typically read-only for a class). +.It Va bio_inbed +Number of finished +.Vt bio +clones. +.It Va bio_parent +Pointer to parent +.Vt bio . +.El +.Pp +The +.Fn g_new_bio +function allocates a new, empty +.Vt bio +structure. +.Pp +.Fn g_alloc_bio +- same as +.Fn g_new_bio , +but always succeeds (allocates bio with the +.Dv M_WAITOK +malloc flag). +.Pp +The +.Fn g_clone_bio +function allocates a new +.Vt bio +structure and copies the following fields from the +.Vt bio +given as an argument to clone: +.Va bio_cmd , +.Va bio_length , +.Va bio_offset , +.Va bio_data , +.Va bio_attribute . +The field +.Va bio_parent +in the clone points to the passed +.Vt bio +and the field +.Va bio_children +in the passed +.Vt bio +is incremented. +.Pp +This function should be used for every request which enters through +the provider of a particular geom and needs to be scheduled down. +Proper order is: +.Pp +.Bl -enum -compact +.It +Clone the received +.Vt "struct bio" . +.It +Modify the clone. +.It +Schedule the clone on its own consumer. +.El +.Pp +.Fn g_duplicate_bio +- same as +.Fn g_clone_bio , +but always succeeds (allocates bio with the +.Dv M_WAITOK +malloc flag). +.Pp +The +.Fn g_destroy_bio +function deallocates and destroys the given +.Vt bio +structure. +.Pp +The +.Fn g_print_bio +function prints information about the given +.Vt bio +structure (for debugging purposes). +.Sh RETURN VALUES +The +.Fn g_new_bio +and +.Fn g_clone_bio +functions return a pointer to the allocated +.Vt bio , +or +.Dv NULL +if an error occurred. +.Sh EXAMPLES +Implementation of +.Dq Dv NULL Ns -transformation , +meaning that an I/O request is cloned and scheduled down without any +modifications. +Let us assume that field +.Va ex_consumer +in structure +.Vt example_softc +contains a consumer attached to the provider we want to operate on. +.Bd -literal -offset indent +void +example_start(struct bio *bp) +{ + struct example_softc *sc; + struct bio *cbp; + + printf("Request received: "); + g_print_bio(bp); + printf("\\n"); + + sc = bp->bio_to->geom->softc; + if (sc == NULL) { + g_io_deliver(bp, ENXIO); + return; + } + + /* Let's clone our bio request. */ + cbp = g_clone_bio(bp); + if (cbp == NULL) { + g_io_deliver(bp, ENOMEM); + return; + } + cbp->bio_done = g_std_done; /* Standard 'done' function. */ + + /* Ok, schedule it down. */ + /* + * The consumer can be obtained from + * LIST_FIRST(&bp->bio_to->geom->consumers) as well, + * if there is only one in our geom. + */ + g_io_request(cbp, sc->ex_consumer); +} +.Ed +.Sh SEE ALSO +.Xr geom 4 , +.Xr DECLARE_GEOM_CLASS 9 , +.Xr g_access 9 , +.Xr g_attach 9 , +.Xr g_consumer 9 , +.Xr g_data 9 , +.Xr g_event 9 , +.Xr g_geom 9 , +.Xr g_provider 9 , +.Xr g_provider_by_name 9 , +.Xr g_wither_geom 9 +.Sh AUTHORS +.An -nosplit +This manual page was written by +.An Pawel Jakub Dawidek Aq pjd@FreeBSD.org . |