History log of /freebsd-head/sys/sys/fcntl.h
Revision Date Author Comments
e511050769bf39a33bca11e6ec888cc16ddf654b 22-Sep-2020 kib <kib@FreeBSD.org> Add O_RESOLVE_BENEATH and AT_RESOLVE_BENEATH to mimic Linux' RESOLVE_BENEATH.

It is like O_BENEATH, but disables to walk out of the subtree rooted
in the starting directory. O_BENEATH does not care if path walks out
if it returned.

Requested by: Dan Gohman <dev@sunfishcode.online>
PR: 248335
Reviewed by: markj
Tested by: pho
Sponsored by: The FreeBSD Foundation
MFC after: 1 week
Differential revision: https://reviews.freebsd.org/D25886
a1c2e427c840e7270d299071291ad1c3f0da02ed 01-Sep-2020 mjg <mjg@FreeBSD.org> sys: clean up empty lines in .c and .h files
11e74d9fa26b9a1948b06d8cce76932b0ac05212 02-Feb-2020 kevans <kevans@FreeBSD.org> Provide O_SEARCH

O_SEARCH is defined by POSIX [0] to open a directory for searching, skipping
permissions checks on the directory itself after the initial open(). This is
close to the semantics we've historically applied for O_EXEC on a directory,
which is UB according to POSIX. Conveniently, O_SEARCH on a file is also
explicitly undefined behavior according to POSIX, so O_EXEC would be a fine
choice. The spec goes on to state that O_SEARCH and O_EXEC need not be
distinct values, but they're not defined to be the same value.

This was pointed out as an incompatibility with other systems that had made
its way into libarchive, which had assumed that O_EXEC was an alias for
O_SEARCH.

This defines compatibility O_SEARCH/FSEARCH (equivalent to O_EXEC and FEXEC
respectively) and expands our UB for O_EXEC on a directory. O_EXEC on a
directory is checked in vn_open_vnode already, so for completeness we add a
NOEXECCHECK when O_SEARCH has been specified on the top-level fd and do not
re-check that when descending in namei.

[0] https://pubs.opengroup.org/onlinepubs/9699919799/

Reviewed by: kib
Differential Revision: https://reviews.freebsd.org/D23247
fa60d0fc5121c0f566b8f83ab65f428d635cd687 17-Jan-2020 mjg <mjg@FreeBSD.org> vfs: provide F_ISUNIONSTACK as a kludge for libc

Prior to introduction of this op libc's readdir would call fstatfs(2), in
effect unnecessarily copying kilobytes of data just to check fs name and a
mount flag.

Reviewed by: kib (previous version)
Differential Revision: https://reviews.freebsd.org/D23162
13d4dfe478f82d11e0c7d467bf4cd4e03a0112b6 25-Sep-2019 kevans <kevans@FreeBSD.org> [1/3] Add mostly Linux-compatible file sealing support

File sealing applies protections against certain actions
(currently: write, growth, shrink) at the inode level. New fileops are added
to accommodate seals - EINVAL is returned by fcntl(2) if they are not
implemented.

Reviewed by: markj, kib
Differential Revision: https://reviews.freebsd.org/D21391
20d273b44bfbde962a17360eb1be449211af58d6 06-Apr-2019 oshogbo <oshogbo@FreeBSD.org> Introduce funlinkat syscall that always us to check if we are removing
the file associated with the given file descriptor.

Reviewed by: kib, asomers
Reviewed by: cem, jilles, brooks (they reviewed previous version)
Discussed with: pjd, and many others
Differential Revision: https://reviews.freebsd.org/D14567
de9d57cf384b5a6c821d06102c467a23ca8a0691 25-Oct-2018 kib <kib@FreeBSD.org> Implement O_BENEATH and AT_BENEATH.

Flags prevent open(2) and *at(2) vfs syscalls name lookup from
escaping the starting directory. Supposedly the interface is similar
to the same proposed Linux flags.

Reviewed by: jilles (code, previous version of manpages), 0mp (manpages)
Discussed with: allanjude, emaste, jonathan
Sponsored by: The FreeBSD Foundation
Differential revision: https://reviews.freebsd.org/D17547
4736ccfd9c3411d50371d7f21f9450a47c19047e 20-Nov-2017 pfg <pfg@FreeBSD.org> sys: further adoption of SPDX licensing ID tags.

Mainly focus on files that use BSD 3-Clause license.

The Software Package Data Exchange (SPDX) group provides a specification
to make it easier for automated tools to detect and summarize well known
opensource licenses. We are gradually adopting the specification, noting
that the tags are considered only advisory and do not, in any way,
superceed or replace the license texts.

Special thanks to Wind River for providing access to "The Duke of
Highlander" tool: an older (2014) run over FreeBSD tree was useful as a
starting point.
7e6cabd06e6caa6a02eeb86308dc0cb3f27e10da 28-Feb-2017 imp <imp@FreeBSD.org> Renumber copyright clause 4

Renumber cluase 4 to 3, per what everybody else did when BSD granted
them permission to remove clause 3. My insistance on keeping the same
numbering for legal reasons is too pedantic, so give up on that point.

Submitted by: Jan Schaumann <jschauma@stevens.edu>
Pull Request: https://github.com/freebsd/freebsd/pull/96
00d578928eca75be320b36d37543a7e2a4f9fbdb 27-May-2016 grehan <grehan@FreeBSD.org> Create branch for bhyve graphics import.
7d0828c94e6533f7d0d139b0242cf16e417eab8b 17-Jan-2016 kib <kib@FreeBSD.org> When cleaning up from failed adv locking and checking for write, do
not call VOP_CLOSE() manually. Instead, delegate the close to
fo_close() performed as part of the fdrop() on the file failed to
open. For this, finish constructing file on error, in particular, set
f_vnode and f_ops.

Forcibly resetting f_ops to badfileops disabled additional cleanups
performed by fo_close() for some file types, in this case it was noted
that cdevpriv data was corrupted. Since fo_close() call must be
enabled for some file types, it makes more sense to enable it for all
files opened through vn_open_cred().

In collaboration with: pho
Sponsored by: The FreeBSD Foundation
MFC after: 2 weeks
76abdf80abd52cbd12cc65ecf3dde21790190789 22-Dec-2015 kib <kib@FreeBSD.org> Make it possible for the cdevsw d_close() driver method to detect last
close and close due to revoke(2)-like operation.

A new FLASTCLOSE flag indicates that this is last close. FREVOKE is
set for revokes, and FNONBLOCK is also set, same as is already done
for VOP_CLOSE() call from vgonel().

The flags reuse user open(2) flags which are never stored in f_flag,
to not consume bit space in the ABI visible way. Assert this with the
static check.

Requested and reviewed by: bde
Sponsored by: The FreeBSD Foundation
MFC after: 2 weeks
b5fb244c277f505abc33458d438abec0b0820b9b 22-Apr-2015 rodrigc <rodrigc@FreeBSD.org> Support file verification in MAC.

* Add VCREAT flag to indicate when a new file is being created
* Add VVERIFY to indicate verification is required
* Both VCREAT and VVERIFY are only passed on the MAC method vnode_check_open
and are removed from the accmode after
* Add O_VERIFY flag to rtld open of objects
* Add 'v' flag to __sflags to set O_VERIFY flag.

Submitted by: Steve Kiernan <stevek@juniper.net>
Obtained from: Juniper Networks, Inc.
GitHub Pull Request: https://github.com/freebsd/freebsd/pull/27
Relnotes: yes
971ac59143ef0c48c1585ad311940038c45aee98 29-Oct-2014 jilles <jilles@FreeBSD.org> MFC r264628: fcntl.h: Make visible various POSIX.1-2008 features.

Also, remove #if __BSD_VISIBLE where it is redundant. When __BSD_VISIBLE is
defined to 1, __POSIX_VISIBLE, __XSI_VISIBLE and __ISO_C_VISIBLE are also
defined to the newest supported version.

PR: 188173
1cb4e2182c251d1b497c4d4eee73f4a512697e54 17-Apr-2014 jilles <jilles@FreeBSD.org> fcntl.h: Make visible various POSIX.1-2008 features.

Also, remove #if __BSD_VISIBLE where it is redundant. When __BSD_VISIBLE is
defined to 1, __POSIX_VISIBLE, __XSI_VISIBLE and __ISO_C_VISIBLE are also
defined to the newest supported version.

PR: 188173
Reviewed by: pluknet
eb1a5f8de9f7ea602c373a710f531abbf81141c4 21-Feb-2014 gjb <gjb@FreeBSD.org> Move ^/user/gjb/hacking/release-embedded up one directory, and remove
^/user/gjb/hacking since this is likely to be merged to head/ soon.

Sponsored by: The FreeBSD Foundation
6b01bbf146ab195243a8e7d43bb11f8835c76af8 27-Dec-2013 gjb <gjb@FreeBSD.org> Copy head@r259933 -> user/gjb/hacking/release-embedded for initial
inclusion of (at least) arm builds with the release.

Sponsored by: The FreeBSD Foundation
03a89a5fe0a80e1df50027d7d94266daffa41805 25-Aug-2013 jilles <jilles@FreeBSD.org> Fix fcntl F_GETFL F_SETFL for files opened execute-only (O_EXEC).

The FFLAGS and OFLAGS now work correctly also for files opened with O_EXEC.
Except possibly fuse, the other users pass values without O_EXEC set. fuse
appears to assume O_EXEC is handled correctly.

Although F_SETFL may not be commonly used for execute-only file descriptors,
F_GETFL may be useful to find the access mode.
5a2e16924f3798ee7f3bf930c0d43f38f18a69dd 27-Jul-2012 kib <kib@FreeBSD.org> Add F_DUP2FD_CLOEXEC. Apparently Solaris 11 already did this.

Submitted by: Jukka A. Ukkonen <jau iki fi>
PR: standards/169962
MFC after: 1 week
e04825c920221bef72b0adc4386073fe8e20a946 21-Jul-2012 kib <kib@FreeBSD.org> (Incomplete) fixes for symbols visibility issues and style in fcntl.h.

Append '__' prefix to the tag of struct oflock, and put it under BSD
namespace. Structure is needed both by libc and kernel, thus cannot be
hidden under #ifdef _KERNEL.

Move a set of non-standard F_* and O_* constants into BSD namespace.
SUSv4 explicitely allows implemenation to pollute F_* and O_* names
after fcntl.h is included, but it costs us nothing to adhere
to the specification if exact POSIX compliance level is requested by
user code.

Change some spaces after #define to tabs.

Noted by and discussed with: bde
MFC after: 1 week
fb0ee769bd9aa180616ea0ffdb18d9c7bd7a7dfa 19-Jul-2012 kib <kib@FreeBSD.org> Implement F_DUPFD_CLOEXEC command for fcntl(2), specified by SUSv4.

PR: standards/169962
Submitted by: Jukka A. Ukkonen <jau iki fi>
MFC after: 1 week
78c075174e74e727279365476d0d076d6c3e3075 04-Nov-2011 jhb <jhb@FreeBSD.org> Add the posix_fadvise(2) system call. It is somewhat similar to
madvise(2) except that it operates on a file descriptor instead of a
memory region. It is currently only supported on regular files.

Just as with madvise(2), the advice given to posix_fadvise(2) can be
divided into two types. The first type provide hints about data access
patterns and are used in the file read and write routines to modify the
I/O flags passed down to VOP_READ() and VOP_WRITE(). These modes are
thus filesystem independent. Note that to ease implementation (and
since this API is only advisory anyway), only a single non-normal
range is allowed per file descriptor.

The second type of hints are used to hint to the OS that data will or
will not be used. These hints are implemented via a new VOP_ADVISE().
A default implementation is provided which does nothing for the WILLNEED
request and attempts to move any clean pages to the cache page queue for
the DONTNEED request. This latter case required two other changes.
First, a new V_CLEANONLY flag was added to vinvalbuf(). This requests
vinvalbuf() to only flush clean buffers for the vnode from the buffer
cache and to not remove any backing pages from the vnode. This is
used to ensure clean pages are not wired into the buffer cache before
attempting to move them to the cache page queue. The second change adds
a new vm_object_page_cache() method. This method is somewhat similar to
vm_object_page_remove() except that instead of freeing each page in the
specified range, it attempts to move clean pages to the cache queue if
possible.

To preserve the ABI of struct file, the f_cdevpriv pointer is now reused
in a union to point to the currently active advice region if one is
present for regular files.

Reviewed by: jilles, kib, arch@
Approved by: re (kib)
MFC after: 1 month
a6c5138e838c72eab719291f4761da0d60653908 27-Oct-2011 jhb <jhb@FreeBSD.org> Sort function prototypes.
9c9a32d97b41ab9d0cae56c7e428ad6d5cd1302f 18-Apr-2011 mdf <mdf@FreeBSD.org> Add the posix_fallocate(2) syscall. The default implementation in
vop_stdallocate() is filesystem agnostic and will run as slow as a
read/write loop in userspace; however, it serves to correctly
implement the functionality for filesystems that do not implement a
VOP_ALLOCATE.

Note that __FreeBSD_version was already bumped today to 900036 for any
ports which would like to use this function.

Also reserve space in the syscall table for posix_fadvise(2).

Reviewed by: -arch (previous version)
fc2bd01611a5db99f84b5d7f3109b9f9274f548d 25-Mar-2011 kib <kib@FreeBSD.org> Add O_CLOEXEC flag to open(2) and fhopen(2).
The new function fallocf(9), that is renamed falloc(9) with added
flag argument, is provided to facilitate the merge to stable branch.

Reviewed by: jhb
MFC after: 1 week
09f9c897d33c41618ada06fbbcf1a9b3812dee53 19-Oct-2010 jamie <jamie@FreeBSD.org> A new jail(8) with a configuration file, to replace the work currently done
by /etc/rc.d/jail.
f1216d1f0ade038907195fc114b7e630623b402c 19-Mar-2010 delphij <delphij@FreeBSD.org> Create a custom branch where I will be able to do the merge.
3c2bafe65e8458fc5abe508bf9e336768eda01bb 07-Dec-2009 delphij <delphij@FreeBSD.org> MFC revision 197579 and 199617:

Add two new fcntls to enable/disable read-ahead:

- F_READAHEAD: specify the amount for sequential access. The amount is
specified in bytes and is rounded up to nearest block size.
- F_RDAHEAD: Darwin compatible version that use 128KB as the sequential
access size.

A third argument of zero disables the read-ahead behavior.

Please note that the read-ahead amount is also constrainted by sysctl
variable, vfs.read_max, which may need to be raised in order to better
utilize this feature.

Thanks Igor Sysoev for proposing the feature and submitting the original
version, and kib@ for his valuable comments.
79f2f8c774b48d4ef62f92d4a09e80af3ceaca7c 28-Sep-2009 delphij <delphij@FreeBSD.org> Add two new fcntls to enable/disable read-ahead:

- F_READAHEAD: specify the amount for sequential access. The amount is
specified in bytes and is rounded up to nearest block size.
- F_RDAHEAD: Darwin compatible version that use 128KB as the sequential
access size.

A third argument of zero disables the read-ahead behavior.

Please note that the read-ahead amount is also constrainted by sysctl
variable, vfs.read_max, which may need to be raised in order to better
utilize this feature.

Thanks Igor Sysoev for proposing the feature and submitting the original
version, and kib@ for his valuable comments.

Submitted by: Igor Sysoev <is rambler-co ru>
Reviewed by: kib@
MFC after: 1 month
1a759a35f242325e2263831a412a94a6e90ca317 22-Jun-2009 kib <kib@FreeBSD.org> Move definitions of AT_* constants from the middle of the open(2) flags
enumeration.

Noted by: bde
40cb57e44ebefc7049ca738b55723388e0ac4ba9 04-Mar-2009 das <das@FreeBSD.org> Add openat to the POSIX.1-2008 namespace.
f05698585dfff301fe972774bb632c6bdb28da90 28-Feb-2009 ed <ed@FreeBSD.org> Add missing POSIX 1003.1-2008 open(2) flag; O_TTY_INIT.

On FreeBSD, this is the default behaviour. According to the spec, we may
give this flag a value of zero, but I'd rather not do this. If we define
it to a non-zero value, we can always change default behaviour without
changing the ABI. This is very unlikely to happen, though.
19b6af98ec71398e77874582eb84ec5310c7156f 22-Nov-2008 dfr <dfr@FreeBSD.org> Clone Kip's Xen on stable/6 tree so that I can work on improving FreeBSD/amd64
performance in Xen's HVM mode.
cf5320822f93810742e3d4a1ac8202db8482e633 19-Oct-2008 lulf <lulf@FreeBSD.org> - Import the HEAD csup code which is the basis for the cvsmode work.
2d9647914555d3d31ccee642ff2428d08d1dd501 05-Aug-2008 dfr <dfr@FreeBSD.org> MFC: r180025,180064,180069,180217,180743,180779-180780

Implement support for NFS advisory locking in the kernel including correct
semantics for flock(2) style locks.

Sponsored by: Isilon Systems
PR: 94256
41cea6d5ca71b8cf057f9face8055b218b30e18e 26-Jun-2008 dfr <dfr@FreeBSD.org> Re-implement the client side of rpc.lockd in the kernel. This implementation
provides the correct semantics for flock(2) style locks which are used by the
lockf(1) command line tool and the pidfile(3) library. It also implements
recovery from server restarts and ensures that dirty cache blocks are written
to the server before obtaining locks (allowing multiple clients to use file
locking to safely share data).

Sponsored by: Isilon Systems
PR: 94256
MFC after: 2 weeks
0536363c8541b26238166e5c92aa1e95b5301de5 24-Apr-2008 dfr <dfr@FreeBSD.org> MFC: kernel-mode NFS lock manager.
bdc8481556f5026bed1bb54a4a39707388a41901 20-Apr-2008 antoine <antoine@FreeBSD.org> MFC to RELENG_7:
Introduce a new F_DUP2FD command to fcntl(2), for compatibility with
Solaris and AIX.
fcntl(fd, F_DUP2FD, arg) and dup2(fd, arg) are functionnaly equivalent.
Document it.
Add some regression tests (identical to the dup2(2) regression tests).

PR: 120233
Submitted by: Jukka Ukkonen
Approved by: rwaston (mentor)
MFC after: 1 month
693c703a12fbd6080805760eae94c2e13566cdd6 10-Apr-2008 dfr <dfr@FreeBSD.org> MFC: Kernel mode Network Lock Manager.
2ad0eb2d91aa816f59ca8be579d30e4b4a5dc788 31-Mar-2008 kib <kib@FreeBSD.org> Add the libc glue and headers definitions for the *at() syscalls.

Based on the submission by rdivacky,
sponsored by Google Summer of Code 2007
Reviewed by: rwatson, rdivacky
Tested by: pho
9ab7de877c11a4496f6475423a81212c2a412aba 31-Mar-2008 kib <kib@FreeBSD.org> Add the constant definition needed by the implementation of the
openat() and the related syscalls.

Based on the submission by rdivacky,
sponsored by Google Summer of Code 2007
Reviewed by: rwatson, rdivacky
Tested by: pho
79d2dfdaa69db38c43daed9744a6dbd0568189b5 26-Mar-2008 dfr <dfr@FreeBSD.org> Add the new kernel-mode NFS Lock Manager. To use it instead of the
user-mode lock manager, build a kernel with the NFSLOCKD option and
add '-k' to 'rpc_lockd_flags' in rc.conf.

Highlights include:

* Thread-safe kernel RPC client - many threads can use the same RPC
client handle safely with replies being de-multiplexed at the socket
upcall (typically driven directly by the NIC interrupt) and handed
off to whichever thread matches the reply. For UDP sockets, many RPC
clients can share the same socket. This allows the use of a single
privileged UDP port number to talk to an arbitrary number of remote
hosts.

* Single-threaded kernel RPC server. Adding support for multi-threaded
server would be relatively straightforward and would follow
approximately the Solaris KPI. A single thread should be sufficient
for the NLM since it should rarely block in normal operation.

* Kernel mode NLM server supporting cancel requests and granted
callbacks. I've tested the NLM server reasonably extensively - it
passes both my own tests and the NFS Connectathon locking tests
running on Solaris, Mac OS X and Ubuntu Linux.

* Userland NLM client supported. While the NLM server doesn't have
support for the local NFS client's locking needs, it does have to
field async replies and granted callbacks from remote NLMs that the
local client has contacted. We relay these replies to the userland
rpc.lockd over a local domain RPC socket.

* Robust deadlock detection for the local lock manager. In particular
it will detect deadlocks caused by a lock request that covers more
than one blocking request. As required by the NLM protocol, all
deadlock detection happens synchronously - a user is guaranteed that
if a lock request isn't rejected immediately, the lock will
eventually be granted. The old system allowed for a 'deferred
deadlock' condition where a blocked lock request could wake up and
find that some other deadlock-causing lock owner had beaten them to
the lock.

* Since both local and remote locks are managed by the same kernel
locking code, local and remote processes can safely use file locks
for mutual exclusion. Local processes have no fairness advantage
compared to remote processes when contending to lock a region that
has just been unlocked - the local lock manager enforces a strict
first-come first-served model for both local and remote lockers.

Sponsored by: Isilon Systems
PR: 95247 107555 115524 116679
MFC after: 2 weeks
514f31f40ed28fea8fdc190c743417debb0d03b3 08-Mar-2008 antoine <antoine@FreeBSD.org> Introduce a new F_DUP2FD command to fcntl(2), for compatibility with
Solaris and AIX.
fcntl(fd, F_DUP2FD, arg) and dup2(fd, arg) are functionnaly equivalent.
Document it.
Add some regression tests (identical to the dup2(2) regression tests).

PR: 120233
Submitted by: Jukka Ukkonen
Approved by: rwaston (mentor)
MFC after: 1 month
8cd9437636744162d1427275b2fe66cf8ccef25c 08-Jan-2008 jhb <jhb@FreeBSD.org> Add a new file descriptor type for IPC shared memory objects and use it to
implement shm_open(2) and shm_unlink(2) in the kernel:
- Each shared memory file descriptor is associated with a swap-backed vm
object which provides the backing store. Each descriptor starts off with
a size of zero, but the size can be altered via ftruncate(2). The shared
memory file descriptors also support fstat(2). read(2), write(2),
ioctl(2), select(2), poll(2), and kevent(2) are not supported on shared
memory file descriptors.
- shm_open(2) and shm_unlink(2) are now implemented as system calls that
manage shared memory file descriptors. The virtual namespace that maps
pathnames to shared memory file descriptors is implemented as a hash
table where the hash key is generated via the 32-bit Fowler/Noll/Vo hash
of the pathname.
- As an extension, the constant 'SHM_ANON' may be specified in place of the
path argument to shm_open(2). In this case, an unnamed shared memory
file descriptor will be created similar to the IPC_PRIVATE key for
shmget(2). Note that the shared memory object can still be shared among
processes by sharing the file descriptor via fork(2) or sendmsg(2), but
it is unnamed. This effectively serves to implement the getmemfd() idea
bandied about the lists several times over the years.
- The backing store for shared memory file descriptors are garbage
collected when they are not referenced by any open file descriptors or
the shm_open(2) virtual namespace.

Submitted by: dillon, peter (previous versions)
Submitted by: rwatson (I based this on his version)
Reviewed by: alc (suggested converting getmemfd() to shm_open())
9e1925f5605eb84767aaedbc35ab643a8f9f90a5 07-Apr-2004 imp <imp@FreeBSD.org> Remove advertising clause from University of California Regent's license,
per letter dated July 22, 1999.

Approved by: core
aca3c4a9f0555df7106b9e3e1b59a9864ea4c08c 20-Jun-2003 phk <phk@FreeBSD.org> Move FMARK and FDEFER til sys/file.h where they belong.

Order the fields in struct file in sections after their scope.
65b2813872da16eda1767b5afd5d8cc233c9babc 17-Sep-2002 mike <mike@FreeBSD.org> o Add typedefs for mode_t, off_t, pid_t rather than including
<sys/types.h>.
o Use the relatively new visibility primitives for conditionals.
o Make O_SYNC an alias for O_FSYNC.
o Mark the F* names as deprecated.
o Add some comments to note missing POSIX requirements or options.
3b2d03b60a11ce28e58a87212bcccedd306f2c81 19-Mar-2002 alfred <alfred@FreeBSD.org> Remove __P
844237b3960bfbf49070d6371a84f67f9e3366f6 13-Jan-2002 alfred <alfred@FreeBSD.org> SMP Lock struct file, filedesc and the global file list.

Seigo Tanimura (tanimura) posted the initial delta.

I've polished it quite a bit reducing the need for locking and
adapting it for KSE.

Locks:

1 mutex in each filedesc
protects all the fields.
protects "struct file" initialization, while a struct file
is being changed from &badfileops -> &pipeops or something
the filedesc should be locked.

1 mutex in each struct file
protects the refcount fields.
doesn't protect anything else.
the flags used for garbage collection have been moved to
f_gcflag which was the FILLER short, this doesn't need
locking because the garbage collection is a single threaded
container.
could likely be made to use a pool mutex.

1 sx lock for the global filelist.

struct file * fhold(struct file *fp);
/* increments reference count on a file */

struct file * fhold_locked(struct file *fp);
/* like fhold but expects file to locked */

struct file * ffind_hold(struct thread *, int fd);
/* finds the struct file in thread, adds one reference and
returns it unlocked */

struct file * ffind_lock(struct thread *, int fd);
/* ffind_hold, but returns file locked */

I still have to smp-safe the fget cruft, I'll get to that asap.
a179ee09ab9ca2d9d1d09dc4752c53a13609f5e9 24-May-2001 dillon <dillon@FreeBSD.org> This patch implements O_DIRECT about 80% of the way. It takes a patchset
Tor created a while ago, removes the raw I/O piece (that has cache coherency
problems), and adds a buffer cache / VM freeing piece.

Essentially this patch causes O_DIRECT I/O to not be left in the cache, but
does not prevent it from going through the cache, hence the 80%. For
the last 20% we need a method by which the I/O can be issued directly to
buffer supplied by the user process and bypass the buffer cache entirely,
but still maintain cache coherency.

I also have the code working under -stable but the changes made to sys/file.h
may not be MFCable, so an MFC is not on the table yet.

Submitted by: tegge, dillon
16604ab260bd5c8c562cf5d28e190a84abd6ce84 22-Apr-2000 wollman <wollman@FreeBSD.org> Implement POSIX.1b shared memory objects. In this implementation,
shared memory objects are regular files; the shm_open(3) routine
uses fcntl(2) to set a flag on the descriptor which tells mmap(2)
to automatically apply MAP_NOSYNC.

Not objected to by: bde, dillon, dufault, jasone
b42951578188c5aab5c9f8cbcde4a743f8092cdc 02-Apr-2000 cvs2svn <cvs2svn@FreeBSD.org> This commit was manufactured by cvs2svn to create branch 'ALSA'.
15b9bcb121e1f3735a2c98a11afdb52a03301d7e 29-Dec-1999 peter <peter@FreeBSD.org> Change #ifdef KERNEL to #ifdef _KERNEL in the public headers. "KERNEL"
is an application space macro and the applications are supposed to be free
to use it as they please (but cannot). This is consistant with the other
BSD's who made this change quite some time ago. More commits to come.
3b842d34e82312a8004a7ecd65ccdb837ef72ac1 28-Aug-1999 peter <peter@FreeBSD.org> $Id$ -> $FreeBSD$
d5ab1c3759352a4180dfc28b7952eeb389bb3261 06-Apr-1998 peter <peter@FreeBSD.org> Implement a new open(2) flag: O_NOFOLLOW. This will instruct open
to not follow symlinks, but to open a handle on the link itself(!).
As strange as this might sound, it has several useful applications
safe race-free ways of opening files in hostile areas (eg: /tmp, a mode
1777 /var/mail, etc). It also would allow things like fchown() to work
on the link rather than having to implement a new syscall specifically for
that task.

Reviewed by: phk
0506343883d62f6649f7bbaf1a436133cef6261d 11-Jan-1998 cvs2svn <cvs2svn@FreeBSD.org> This commit was manufactured by cvs2svn to create branch 'jb'.
7c6e96080c4fb49bf912942804477d202a53396c 10-Jan-1998 cvs2svn <cvs2svn@FreeBSD.org> This commit was manufactured by cvs2svn to create branch 'JB'.
94b6d727947e1242356988da003ea702d41a97de 22-Feb-1997 peter <peter@FreeBSD.org> Back out part 1 of the MCFH that changed $Id$ to $FreeBSD$. We are not
ready for it yet.
808a36ef658c1810327b5d329469bcf5dad24b28 14-Jan-1997 jkh <jkh@FreeBSD.org> Make the long-awaited change from $Id$ to $FreeBSD$

This will make a number of things easier in the future, as well as (finally!)
avoiding the Id-smashing problem which has plagued developers for so long.

Boy, I'm glad we're not using sup anymore. This update would have been
insane otherwise.
623ea9097a9c438fd452300b19a68333a101c981 29-Nov-1996 bde <bde@FreeBSD.org> Made O_NOCTTY distinct from the other flags (it clashed with O_RDONLY).

Found by: NIST-PCTS
f3dd75a38d66ed54a0f2660b0a27d177fb33f068 30-Jan-1996 mpp <mpp@FreeBSD.org> Fix a bunch of spelling errors in the comment fields of
a bunch of system include files.
86f1bc4514fdcfd255f37f3218fe234bdc3664fc 05-Nov-1995 cvs2svn <cvs2svn@FreeBSD.org> This commit was manufactured by cvs2svn to create branch 'LINUX'.
2e14d9ebc3d3592c67bdf625af9ebe0dfc386653 14-Mar-1995 cvs2svn <cvs2svn@FreeBSD.org> This commit was manufactured by cvs2svn to create branch 'MATT_THOMAS'.
34cd81d75f398ee455e61969b118639dacbfd7a6 23-Sep-1994 cvs2svn <cvs2svn@FreeBSD.org> This commit was manufactured by cvs2svn to create branch 'MACKERRAS'.
e16baf7a5fe7ac1453381d0017ed1dcdeefbc995 07-Aug-1994 cvs2svn <cvs2svn@FreeBSD.org> This commit was manufactured by cvs2svn to create branch 'SUNRPC'.
8d205697aac53476badf354623abd4e1c7bc5aff 02-Aug-1994 dg <dg@FreeBSD.org> Added $Id$
8fb65ce818b3e3c6f165b583b910af24000768a5 24-May-1994 rgrimes <rgrimes@FreeBSD.org> BSD 4.4 Lite Kernel Sources