freebsd kernel with SKQ
41014d996a
perform copyin/copyout of the file data into the usermode buffer. Typical filesystem hold vnode lock and some buffer locks over the VOP_READ() and VOP_WRITE() operations, and since page fault handler may need to recurse into VFS to get the page content, a deadlock is possible. The facility works by disabling page faults handling for the current thread and attempting to execute i/o while allowing uiomove() to access the usermode mapping of the i/o buffer. If all buffer pages are resident, uiomove() is successfull and request is finished. If EFAULT is returned from uiomove(), the pages backing i/o buffer are faulted in and held, and the copyin/out is performed using uiomove_fromphys() over the held pages for the second attempt of VOP call. Since pages are hold in chunks to prevent large i/o requests from starving free pages pool, and since vnode lock is only taken for i/o over the current chunk, the vnode lock no longer protect atomicity of the whole i/o request. Use newly added rangelocks to provide the required atomicity of i/o regardind other i/o and truncations. Filesystems need to explicitely opt-in into the scheme, by setting the MNTK_NO_IOPF struct mount flag, and optionally by using vn_io_fault_uiomove(9) helper which takes care of calling uiomove() or converting uio into request for uiomove_fromphys(). Reviewed by: bf (comments), mdf, pjd (previous version) Tested by: pho Tested by: flo, Gustau P?rez <gperez entel upc edu> (previous version) MFC after: 2 months |
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| bin | ||
| cddl | ||
| contrib | ||
| crypto | ||
| etc | ||
| games | ||
| gnu | ||
| include | ||
| kerberos5 | ||
| lib | ||
| libexec | ||
| release | ||
| rescue | ||
| sbin | ||
| secure | ||
| share | ||
| sys | ||
| tools | ||
| usr.bin | ||
| usr.sbin | ||
| COPYRIGHT | ||
| LOCKS | ||
| MAINTAINERS | ||
| Makefile | ||
| Makefile.inc1 | ||
| ObsoleteFiles.inc | ||
| README | ||
| UPDATING | ||
This is the top level of the FreeBSD source directory. This file was last revised on: $FreeBSD$ For copyright information, please see the file COPYRIGHT in this directory (additional copyright information also exists for some sources in this tree - please see the specific source directories for more information). The Makefile in this directory supports a number of targets for building components (or all) of the FreeBSD source tree, the most commonly used one being ``world'', which rebuilds and installs everything in the FreeBSD system from the source tree except the kernel, the kernel-modules and the contents of /etc. The ``world'' target should only be used in cases where the source tree has not changed from the currently running version. See: http://www.freebsd.org/doc/en_US.ISO8859-1/books/handbook/makeworld.html for more information, including setting make(1) variables. The ``buildkernel'' and ``installkernel'' targets build and install the kernel and the modules (see below). Please see the top of the Makefile in this directory for more information on the standard build targets and compile-time flags. Building a kernel is a somewhat more involved process, documentation for which can be found at: http://www.freebsd.org/doc/en_US.ISO8859-1/books/handbook/kernelconfig.html And in the config(8) man page. Note: If you want to build and install the kernel with the ``buildkernel'' and ``installkernel'' targets, you might need to build world before. More information is available in the handbook. The sample kernel configuration files reside in the sys/<arch>/conf sub-directory (assuming that you've installed the kernel sources), the file named GENERIC being the one used to build your initial installation kernel. The file NOTES contains entries and documentation for all possible devices, not just those commonly used. It is the successor of the ancient LINT file, but in contrast to LINT, it is not buildable as a kernel but a pure reference and documentation file. Source Roadmap: --------------- bin System/user commands. cddl Various commands and libraries under the Common Development and Distribution License. contrib Packages contributed by 3rd parties. crypto Cryptography stuff (see crypto/README). etc Template files for /etc. games Amusements. gnu Various commands and libraries under the GNU Public License. Please see gnu/COPYING* for more information. include System include files. kerberos5 Kerberos5 (Heimdal) package. lib System libraries. libexec System daemons. release Release building Makefile & associated tools. rescue Build system for statically linked /rescue utilities. sbin System commands. secure Cryptographic libraries and commands. share Shared resources. sys Kernel sources. tools Utilities for regression testing and miscellaneous tasks. usr.bin User commands. usr.sbin System administration commands. For information on synchronizing your source tree with one or more of the FreeBSD Project's development branches, please see: http://www.freebsd.org/doc/en_US.ISO8859-1/books/handbook/synching.html