| Message ID | 20230609115858.4737-1-sergei.shtepa@veeam.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v4,01/11] documentation: Block Device Filtering Mechanism | expand |
Hi-- On 6/9/23 04:58, Sergei Shtepa wrote: > The document contains: > * Describes the purpose of the mechanism > * A little historical background on the capabilities of handling I/O > units of the Linux kernel > * Brief description of the design > * Reference to interface description > > Reviewed-by: Bagas Sanjaya <bagasdotme@gmail.com> > Signed-off-by: Sergei Shtepa <sergei.shtepa@veeam.com> > --- > Documentation/block/blkfilter.rst | 64 +++++++++++++++++++++++++++++++ > Documentation/block/index.rst | 1 + > MAINTAINERS | 6 +++ > 3 files changed, 71 insertions(+) > create mode 100644 Documentation/block/blkfilter.rst > > diff --git a/Documentation/block/blkfilter.rst b/Documentation/block/blkfilter.rst > new file mode 100644 > index 000000000000..555625789244 > --- /dev/null > +++ b/Documentation/block/blkfilter.rst > @@ -0,0 +1,64 @@ > +.. SPDX-License-Identifier: GPL-2.0 > + > +================================ > +Block Device Filtering Mechanism > +================================ > + > +The block device filtering mechanism is an API that allows to attach block that allows {what or who} to attach so who/what does the attach? Is it a driver or a user or admin or something else? and attach them to what? > +device filters. Block device filters allow perform additional processing allow performing ... > +for I/O units. > + > +Introduction > +============ > + > +The idea of handling I/O units on block devices is not new. Back in the > +2.6 kernel, there was an undocumented possibility of handling I/O units > +by substituting the make_request_fn() function, which belonged to the > +request_queue structure. But none of the in-tree kernel modules used this > +feature, and it was eliminated in the 5.10 kernel. > + > +The block device filtering mechanism returns the ability to handle I/O units. > +It is possible to safely attach filter to a block device "on the fly" without attach a filter or attach filters > +changing the structure of block devices stack. of the block device's stack. > + > +It supports attaching one filter to one block device, because there is only > +one filter implementation in the kernel yet. > +See Documentation/block/blksnap.rst. > + > +Design > +====== > + > +The block device filtering mechanism provides registration and unregistration > +for filter operations. The struct blkfilter_operations contains a pointer to > +the callback functions for the filter. After registering the filter operations, > +filter can be managed using block device ioctl BLKFILTER_ATTACH, a filter or the filter ioctls > +BLKFILTER_DETACH and BLKFILTER_CTL. > + > +When the filter is attached, the callback function is called for each I/O unit > +for a block device, providing I/O unit filtering. Depending on the result of > +filtering the I/O unit, it can either be passed for subsequent processing by > +the block layer, or skipped. > + > +The filter can be implemented as a loadable module. In this case, the filter > +module cannot be unloaded while the filter is attached to at least one of the > +block devices. > + > +Interface description > +===================== > + > +The ioctl BLKFILTER_ATTACH and BLKFILTER_DETACH use structure blkfilter_name. ioctls > +It allows to attach a filter to a block device or detach it. It allows a driver to attach a filter ... ? > + > +The ioctl BLKFILTER_CTL use structure blkfilter_ctl. It allows to send a It allows a driver to send a > +filter-specific command. > + > +.. kernel-doc:: include/uapi/linux/blk-filter.h > + > +To register in the system, the filter creates its own account, which contains > +callback functions, unique filter name and module owner. This filter account is > +used by the registration functions. I'm having a problem with this "account" thingy. Can you explain more about it? Is there an alternate word that might be used here? > + > +.. kernel-doc:: include/linux/blk-filter.h > + > +.. kernel-doc:: block/blk-filter.c > + :export: Thanks.
Thank you very much, Randy, for the work you've done. Sometimes I want to compile the documentation into bytecode, fix the warnings and debug it in the debugger. On 6/13/23 03:52, Randy Dunlap wrote: > Subject: > Re: [PATCH v4 01/11] documentation: Block Device Filtering Mechanism > From: > Randy Dunlap <rdunlap@infradead.org> > Date: > 6/13/23, 03:52 > > To: > Sergei Shtepa <sergei.shtepa@veeam.com>, axboe@kernel.dk, hch@infradead.org, corbet@lwn.net, snitzer@kernel.org > CC: > viro@zeniv.linux.org.uk, brauner@kernel.org, willy@infradead.org, dlemoal@kernel.org, wsa@kernel.org, heikki.krogerus@linux.intel.com, ming.lei@redhat.com, gregkh@linuxfoundation.org, linux-block@vger.kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, Bagas Sanjaya <bagasdotme@gmail.com> > > > Hi-- > > On 6/9/23 04:58, Sergei Shtepa wrote: >> The document contains: >> * Describes the purpose of the mechanism >> * A little historical background on the capabilities of handling I/O >> units of the Linux kernel >> * Brief description of the design >> * Reference to interface description >> >> Reviewed-by: Bagas Sanjaya <bagasdotme@gmail.com> >> Signed-off-by: Sergei Shtepa <sergei.shtepa@veeam.com> >> --- >> Documentation/block/blkfilter.rst | 64 +++++++++++++++++++++++++++++++ >> Documentation/block/index.rst | 1 + >> MAINTAINERS | 6 +++ >> 3 files changed, 71 insertions(+) >> create mode 100644 Documentation/block/blkfilter.rst >> >> diff --git a/Documentation/block/blkfilter.rst b/Documentation/block/blkfilter.rst >> new file mode 100644 >> index 000000000000..555625789244 >> --- /dev/null >> +++ b/Documentation/block/blkfilter.rst >> @@ -0,0 +1,64 @@ >> +.. SPDX-License-Identifier: GPL-2.0 >> + >> +================================ >> +Block Device Filtering Mechanism >> +================================ >> + >> +The block device filtering mechanism is an API that allows to attach block > that allows {what or who} to attach > > so who/what does the attach? Is it a driver or a user or admin or something else? > and attach them to what? > >> +device filters. Block device filters allow perform additional processing > allow performing ... > >> +for I/O units. >> + >> +Introduction >> +============ >> + >> +The idea of handling I/O units on block devices is not new. Back in the >> +2.6 kernel, there was an undocumented possibility of handling I/O units >> +by substituting the make_request_fn() function, which belonged to the >> +request_queue structure. But none of the in-tree kernel modules used this >> +feature, and it was eliminated in the 5.10 kernel. >> + >> +The block device filtering mechanism returns the ability to handle I/O units. >> +It is possible to safely attach filter to a block device "on the fly" without > attach a filter > or > attach filters > >> +changing the structure of block devices stack. > of the block device's stack. > >> + >> +It supports attaching one filter to one block device, because there is only >> +one filter implementation in the kernel yet. >> +See Documentation/block/blksnap.rst. >> + >> +Design >> +====== >> + >> +The block device filtering mechanism provides registration and unregistration >> +for filter operations. The struct blkfilter_operations contains a pointer to >> +the callback functions for the filter. After registering the filter operations, >> +filter can be managed using block device ioctl BLKFILTER_ATTACH, > a filter > or > the filter ioctls > >> +BLKFILTER_DETACH and BLKFILTER_CTL. >> + >> +When the filter is attached, the callback function is called for each I/O unit >> +for a block device, providing I/O unit filtering. Depending on the result of >> +filtering the I/O unit, it can either be passed for subsequent processing by >> +the block layer, or skipped. >> + >> +The filter can be implemented as a loadable module. In this case, the filter >> +module cannot be unloaded while the filter is attached to at least one of the >> +block devices. >> + >> +Interface description >> +===================== >> + >> +The ioctl BLKFILTER_ATTACH and BLKFILTER_DETACH use structure blkfilter_name. > ioctls > >> +It allows to attach a filter to a block device or detach it. > It allows a driver to attach a filter ... > ? > >> + >> +The ioctl BLKFILTER_CTL use structure blkfilter_ctl. It allows to send a > It allows a driver to send a > >> +filter-specific command. >> + >> +.. kernel-doc:: include/uapi/linux/blk-filter.h >> + >> +To register in the system, the filter creates its own account, which contains >> +callback functions, unique filter name and module owner. This filter account is >> +used by the registration functions. > I'm having a problem with this "account" thingy. Can you explain more about it? > Is there an alternate word that might be used here? > >> + >> +.. kernel-doc:: include/linux/blk-filter.h >> + >> +.. kernel-doc:: block/blk-filter.c >> + :export: > Thanks. > -- ~Randy > fix of the blkfilter.rst document and help in Kconfig for blksnap Reported-by: Randy Dunlap <rdunlap@infradead.org> Signed-off-by: Sergei Shtepa <sergei.shtepa@veeam.com> --- Documentation/block/blkfilter.rst | 28 +++++++++++++++------------- drivers/block/blksnap/Kconfig | 2 +- 2 files changed, 16 insertions(+), 14 deletions(-) diff --git a/Documentation/block/blkfilter.rst b/Documentation/block/blkfilter.rst index 555625789244..b5160d1008fd 100644 --- a/Documentation/block/blkfilter.rst +++ b/Documentation/block/blkfilter.rst @@ -4,8 +4,8 @@ Block Device Filtering Mechanism ================================ -The block device filtering mechanism is an API that allows to attach block -device filters. Block device filters allow perform additional processing +The block device filtering mechanism provides the ability to attach block +device filters. Block device filters allow performing additional processing for I/O units. Introduction @@ -18,8 +18,8 @@ request_queue structure. But none of the in-tree kernel modules used this feature, and it was eliminated in the 5.10 kernel. The block device filtering mechanism returns the ability to handle I/O units. -It is possible to safely attach filter to a block device "on the fly" without -changing the structure of block devices stack. +It is possible to safely attach a filter to a block device "on the fly" without +changing the structure of the block device's stack. It supports attaching one filter to one block device, because there is only one filter implementation in the kernel yet. @@ -31,7 +31,7 @@ Design The block device filtering mechanism provides registration and unregistration for filter operations. The struct blkfilter_operations contains a pointer to the callback functions for the filter. After registering the filter operations, -filter can be managed using block device ioctl BLKFILTER_ATTACH, +the filter can be managed using block device ioctls BLKFILTER_ATTACH, BLKFILTER_DETACH and BLKFILTER_CTL. When the filter is attached, the callback function is called for each I/O unit @@ -46,17 +46,19 @@ block devices. Interface description ===================== -The ioctl BLKFILTER_ATTACH and BLKFILTER_DETACH use structure blkfilter_name. -It allows to attach a filter to a block device or detach it. - -The ioctl BLKFILTER_CTL use structure blkfilter_ctl. It allows to send a -filter-specific command. +The ioctl BLKFILTER_ATTACH allows user-space programs to attach a block device +filter to a block device. The ioctl BLKFILTER_DETACH allows user-space programs +to detach it. Both ioctls use structure blkfilter_name. The ioctl BLKFILTER_CTL +allows user-space programs to send a filter-specific command. It use structure +blkfilter_ctl. .. kernel-doc:: include/uapi/linux/blk-filter.h -To register in the system, the filter creates its own account, which contains -callback functions, unique filter name and module owner. This filter account is -used by the registration functions. +To register in the system, the filter uses the blkfilter_operations structure, +which contains callback functions, unique filter name and module owner. When +attaching a filter to a block device, the filter creates a blkfilter structure. +The pointer to the blkfilter structure allows the filter to determine for +which block device the callback functions are being called. .. kernel-doc:: include/linux/blk-filter.h diff --git a/drivers/block/blksnap/Kconfig b/drivers/block/blksnap/Kconfig index 14081359847b..11df0886489d 100644 --- a/drivers/block/blksnap/Kconfig +++ b/drivers/block/blksnap/Kconfig @@ -8,5 +8,5 @@ config BLKSNAP help Allow to create snapshots and track block changes for block devices. Designed for creating backups for simple block devices. Snapshots are - temporary and are released then backup is completed. Change block + temporary and are released when backup is completed. Change block tracking allows to create incremental or differential backups.
diff --git a/Documentation/block/blkfilter.rst b/Documentation/block/blkfilter.rst new file mode 100644 index 000000000000..555625789244 --- /dev/null +++ b/Documentation/block/blkfilter.rst @@ -0,0 +1,64 @@ +.. SPDX-License-Identifier: GPL-2.0 + +================================ +Block Device Filtering Mechanism +================================ + +The block device filtering mechanism is an API that allows to attach block +device filters. Block device filters allow perform additional processing +for I/O units. + +Introduction +============ + +The idea of handling I/O units on block devices is not new. Back in the +2.6 kernel, there was an undocumented possibility of handling I/O units +by substituting the make_request_fn() function, which belonged to the +request_queue structure. But none of the in-tree kernel modules used this +feature, and it was eliminated in the 5.10 kernel. + +The block device filtering mechanism returns the ability to handle I/O units. +It is possible to safely attach filter to a block device "on the fly" without +changing the structure of block devices stack. + +It supports attaching one filter to one block device, because there is only +one filter implementation in the kernel yet. +See Documentation/block/blksnap.rst. + +Design +====== + +The block device filtering mechanism provides registration and unregistration +for filter operations. The struct blkfilter_operations contains a pointer to +the callback functions for the filter. After registering the filter operations, +filter can be managed using block device ioctl BLKFILTER_ATTACH, +BLKFILTER_DETACH and BLKFILTER_CTL. + +When the filter is attached, the callback function is called for each I/O unit +for a block device, providing I/O unit filtering. Depending on the result of +filtering the I/O unit, it can either be passed for subsequent processing by +the block layer, or skipped. + +The filter can be implemented as a loadable module. In this case, the filter +module cannot be unloaded while the filter is attached to at least one of the +block devices. + +Interface description +===================== + +The ioctl BLKFILTER_ATTACH and BLKFILTER_DETACH use structure blkfilter_name. +It allows to attach a filter to a block device or detach it. + +The ioctl BLKFILTER_CTL use structure blkfilter_ctl. It allows to send a +filter-specific command. + +.. kernel-doc:: include/uapi/linux/blk-filter.h + +To register in the system, the filter creates its own account, which contains +callback functions, unique filter name and module owner. This filter account is +used by the registration functions. + +.. kernel-doc:: include/linux/blk-filter.h + +.. kernel-doc:: block/blk-filter.c + :export: diff --git a/Documentation/block/index.rst b/Documentation/block/index.rst index 9fea696f9daa..e9712f72cd6d 100644 --- a/Documentation/block/index.rst +++ b/Documentation/block/index.rst @@ -10,6 +10,7 @@ Block bfq-iosched biovecs blk-mq + blkfilter cmdline-partition data-integrity deadline-iosched diff --git a/MAINTAINERS b/MAINTAINERS index 250518fc70ff..f85f21487364 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -3583,6 +3583,12 @@ M: Jan-Simon Moeller <jansimon.moeller@gmx.de> S: Maintained F: drivers/leds/leds-blinkm.c +BLOCK DEVICE FILTERING MECHANISM +M: Sergei Shtepa <sergei.shtepa@veeam.com> +L: linux-block@vger.kernel.org +S: Supported +F: Documentation/block/blkfilter.rst + BLOCK LAYER M: Jens Axboe <axboe@kernel.dk> L: linux-block@vger.kernel.org