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Add coredump capability for the ELF-FDPIC binfmt.
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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Move the roundup() macro from binfmt_elf.c into linux/kernel.h as it's
generally useful.
[akpm@osdl.org: nuke all the other implementations]
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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Adjust the ELF-FDPIC binfmt driver to conform much more to the CodingStyle,
silly though it may be.
Further changes:
(*) Drop the casts to long for addresses in kdebug() statements (they're
unsigned long already).
(*) Use extra variables to avoid expressions longer than 80 chars by splitting
the statement into multiple statements and letting the compiler optimise
them back together.
(*) Eliminate duplicate call of ksize() when working out how much space was
actually allocated for the stack.
(*) Discard the commented-out load_shlib prototype and op pointer as this will
not be supported in ELF-FDPIC for the foreseeable future.
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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Fix execution through the FDPIC binfmt of programs stored on ramfs by
preventing the ramfs mmap() returning successfully on a private mapping of
a ramfs file. This causes NOMMU mmap to make a copy of the mapped portion
of the file and map that instead.
This could be improved by granting direct mapping access to read-only
private mappings for which the data is stored on a contiguous run of pages.
However, this is only likely to be the case if the file was extended with
truncate before being written.
ramfs is left to map the file directly for shared mappings so that SYSV IPC
and POSIX shared memory both still work.
Signed-off-by: David Howells <dhowells@redhat.com>
Cc: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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Fix FDPIC compile errors.
(akpm: we suspect it fixes a warning)
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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virtual area
Sometimes, applications need below call to be successful although
"/mnt/hugepages/file1" doesn't exist.
fd = open("/mnt/hugepages/file1", O_CREAT|O_RDWR, 0755);
*addr = mmap(NULL, 0x1024*1024*256, PROT_NONE, 0, fd, 0);
As for regular pages (or files), above call does work, but as for huge
pages, above call would fail because hugetlbfs_file_mmap would fail if
(!(vma->vm_flags & VM_WRITE) && len > inode->i_size).
This capability on huge page is useful on ia64 when the process wants to
protect one area on region 4, so other threads couldn't read/write this
area. A famous JVM (Java Virtual Machine) implementation on IA64 needs the
capability.
Signed-off-by: Zhang Yanmin <yanmin.zhang@intel.com>
Cc: David Gibson <david@gibson.dropbear.id.au>
Cc: Hugh Dickins <hugh@veritas.com>
[ Expand-on-mmap semantics again... this time matching normal fs's. wli ]
Acked-by: William Lee Irwin III <wli@holomorphy.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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This patch marks an unused export as EXPORT_UNUSED_SYMBOL.
Signed-off-by: Adrian Bunk <bunk@stusta.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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Change the partition code in fs/partitions/check.c to initialize a newly
detected partition's policy field with that of the containing block device
(see patch below).
My reasoning is that function set_disk_ro() in block/genhd.c modifies the
policy field (read-only indicator) of a disk and all contained partitions.
When a partition is detected after the call to set_disk_ro(), the policy
field of this partition will currently not inherit the disk's policy field.
This behavior poses a problem in cases where a block device can be
'logically de- and reactivated' like e.g. the s390 DASD driver because
partition detection may run after the policy field has been modified.
Signed-off-by: Peter Oberparleiter <peter.oberparleiter@de.ibm.com>
Acked-by: Al Viro <viro@ftp.linux.org.uk>
Makes-sense-to: Jens Axboe <axboe@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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When write() extends a file(i_size is increased) and fsync() is called,
change of inode must be written to journaling area through fsync().
But,currently the i_trans_id is not correctly updated when i_size is
increased. So fsync() does not kick the journal writer.
Reiserfs_file_write() already updates the transaction when blocks are
allocated, but the case when i_size increases and new blocks are not added
is not correctly treated.
Following patch fix this bug.
Signed-off-by: Hisashi Hifumi <hifumi.hisashi@oss.ntt.co.jp>
Cc: Jeff Mahoney <jeffm@suse.com>
Cc: Chris Mason <mason@suse.com>
Cc: Hans Reiser <reiser@namesys.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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In the case when compiling via a symlink tree, we want to ensure that the
close-to-open GETATTR call is applied only to the final file, and not to
the symlink.
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
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The introduction of the FLUSH_INVALIDATE argument to nfs_sync_inode_wait()
does not clear the nr_unstable page state counter for pages that are being
released.
Also fix a longstanding similar bug when nfs_commit_list() fails.
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
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Use FL_ACCESS flag to test and/or wait for local locks before we try
requesting a lock from the server
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
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Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
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Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
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Use the new behaviour of {flock,posix}_file_lock(F_UNLCK) to determine if
we held a lock, and only send the RPC request to the server if this was the
case.
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
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Change posix_lock_file_conf(), and flock_lock_file() so that if called
with an F_UNLCK argument, and the FL_EXISTS flag they will indicate
whether or not any locks were actually freed by returning 0 or -ENOENT.
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
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Fix changed name of proc_task() to get_proc_task().
Signed-off-by: Greg Ungerer <gerg@uclinux.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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* git://git.infradead.org/mtd-2.6:
[JFFS2][XATTR] Fix memory leak in POSIX-ACL support
fs/jffs2/: make 2 functions static
[MTD] NAND: Fix broken sharpsl driver
[JFFS2][XATTR] Fix xd->refcnt race condition
MTD: kernel-doc fixes + additions
MTD: fix all kernel-doc warnings
[MTD] DOC: Fixup read functions and do a little cleanup
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cleanup: remove task_t and convert all the uses to struct task_struct. I
introduced it for the scheduler anno and it was a mistake.
Conversion was mostly scripted, the result was reviewed and all
secondary whitespace and style impact (if any) was fixed up by hand.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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Teach special (recursive) locking code to the lock validator.
Effects on non-lockdep kernels:
- the introduction of the following function variants:
extern struct block_device *open_partition_by_devnum(dev_t, unsigned);
extern int blkdev_put_partition(struct block_device *);
static int
blkdev_get_whole(struct block_device *bdev, mode_t mode, unsigned flags);
which on non-lockdep are the same as open_by_devnum(), blkdev_put()
and blkdev_get().
- a subclass parameter to do_open(). [unused on non-lockdep]
- a subclass parameter to __blkdev_put(), which is a new internal
function for the main blkdev_put*() functions. [parameter unused
on non-lockdep kernels, except for two sanity check WARN_ON()s]
these functions carry no semantical difference - they only express
object dependencies towards the lockdep subsystem.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Cc: Neil Brown <neilb@cse.unsw.edu.au>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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The s_umount rwsem needs to be classified as per-superblock since it's
perfectly legit to keep multiple of those recursively in the VFS locking
rules.
Has no effect on non-lockdep kernels.
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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Teach special (per-filesystem) locking code to the lock validator.
Minimal effect on non-lockdep kernels: one extra parameter to alloc_super().
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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The quota code plays interesting games with the lock ordering; to quote Jan:
| i_mutex of inode containing quota file is acquired after all other
| quota locks. i_mutex of all other inodes is acquired before quota
| locks. Quota code makes sure (by resetting inode operations and
| setting special flag on inode) that noone tries to enter quota code
| while holding i_mutex on a quota file...
The good news is that all of this special case i_mutex grabbing happens in the
(per filesystem) low level quota write function. For this special case we
need a new I_MUTEX_* nesting level, since this just entirely outside any of
the regular VFS locking rules for i_mutex. I trust Jan on his blue eyes that
this is not ever going to deadlock; and based on that the patch below is what
it takes to inform lockdep of these very interesting new locking rules.
The new locking rule for the I_MUTEX_QUOTA nesting level is that this is the
deepest possible level of nesting for i_mutex, and that this only should be
used in quota write (and possibly read) function of filesystems. This makes
the lock ordering of the I_MUTEX_* levels:
I_MUTEX_PARENT -> I_MUTEX_CHILD -> I_MUTEX_NORMAL -> I_MUTEX_QUOTA
Has no effect on non-lockdep kernels.
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Acked-by: Ingo Molnar <mingo@elte.hu>
Cc: Jan Kara <jack@ucw.cz>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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NTFS uses lots of type-opaque objects which acquire their true identity
runtime - so the lock validator needs to be helped in a couple of places to
figure out object types.
Many thanks to Anton Altaparmakov for giving lots of explanations about NTFS
locking rules.
Has no effect on non-lockdep kernels.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Anton Altaparmakov <aia21@cantab.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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Teach special (recursive) locking code to the lock validator. Has no effect
on non-lockdep kernels.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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Teach special (recursive) locking code to the lock validator. Has no effect
on non-lockdep kernels.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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Teach special (rwsem-in-irq) locking code to the lock validator. Has no
effect on non-lockdep kernels.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Cc: Russell King <rmk@arm.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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Locking init improvement:
- introduce and use __SPIN_LOCK_UNLOCKED for array initializations,
to pass in the name string of locks, used by debugging
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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Fix check for bad address; use macro instead of open-coding two checks.
Taken from RHEL4 kernel update.
From: Ernie Petrides <petrides@redhat.com>
For background, the BAD_ADDR() macro should return TRUE if the address is
TASK_SIZE, because that's the lowest address that is *not* valid for
user-space mappings. The macro was correct in binfmt_aout.c but was wrong
for the "equal to" case in binfmt_elf.c. There were two in-line validations
of user-space addresses in binfmt_elf.c, which have been appropriately
converted to use the corrected BAD_ADDR() macro in the patch you posted
yesterday. Note that the size checks against TASK_SIZE are okay as coded.
The additional changes that I propose are below. These are in the error
paths for bad ELF entry addresses once load_elf_binary() has already
committed to exec'ing the new image (following the tearing down of the
task's original address space).
The 1st hunk deals with the interp-side of the outer "if". There were two
problems here. The printk() should be removed because this path can be
triggered at will by a bogus interpreter image created and used by a
malicious user. Further, the error code should not be ENOEXEC, because that
causes the loop in search_binary_handler() to continue trying other exec
handlers (twice, in fact). But it's too late for this to work correctly,
because the user address space has already been torn down, and an exec()
failure cannot be returned to the user code because the code no longer
exists. The only recovery is to force a SIGSEGV, but it's best to terminate
the search loop immediately. I somewhat arbitrarily chose EINVAL as a
fallback error code, but any error returned by load_elf_interp() will
override that (but this value will never be seen by user-space).
The 2nd hunk deals with the non-interp-side of the outer "if". There were
two problems here as well. The SIGSEGV needs to be forced, because a prior
sigaction() syscall might have set the associated disposition to SIG_IGN.
And the ENOEXEC should be changed to EINVAL as described above.
Signed-off-by: Chuck Ebbert <76306.1226@compuserve.com>
Signed-off-by: Ernie Petrides <petrides@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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This fixes a bug in fs/nfs which makes it impossible to build nfs
without having procfs enabled.
Signed-off-by: Dominik Hackl <dominik@hackl.dhs.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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jffs2_clear_acl() which releases acl caches allocated by kmalloc()
was defined but it was never called. Thus, we faced to the risk
of memory leaking.
This patch plugs jffs2_clear_acl() into jffs2_do_clear_inode().
It ensures to release acl cache when inode is cleared.
Signed-off-by: KaiGai Kohei <kaigai@ak.jp.nec.com>
Signed-off-by: David Woodhouse <dwmw2@infradead.org>
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Reiserfs does not update ctime and mtime on expanding truncate via
truncate(). This patch fixes it.
Signed-off-by: Vladimir Saveliev <vs@namesys.com>
Cc: Hans Reiser <reiser@namesys.com>
Cc: Michael Kerrisk <mtk-manpages@gmx.net>
Cc: Chris Mason <mason@suse.com>
Cc: Jeff Mahoney <jeffm@suse.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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This patch fixes buggy behaviour of UFS
in such kind of scenario:
open(, O_TRUNC...)
ftruncate(, 1024)
ftruncate(, 0)
Such a scenario causes ufs_panic and remount read-only. This happen
because of according to specification UFS should always allocate block for
last byte, and many parts of our implementation rely on this, but
`ufs_truncate' doesn't care about this.
To make possible return error code and to know about old size, this patch
removes `truncate' from ufs inode_operations and uses `setattr' method to
call ufs_truncate.
Signed-off-by: Evgeniy Dushistov <dushistov@mail.ru>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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* git://git.kernel.org/pub/scm/linux/kernel/git/bunk/trivial:
Remove obsolete #include <linux/config.h>
remove obsolete swsusp_encrypt
arch/arm26/Kconfig typos
Documentation/IPMI typos
Kconfig: Typos in net/sched/Kconfig
v9fs: do not include linux/version.h
Documentation/DocBook/mtdnand.tmpl: typo fixes
typo fixes: specfic -> specific
typo fixes in Documentation/networking/pktgen.txt
typo fixes: occuring -> occurring
typo fixes: infomation -> information
typo fixes: disadvantadge -> disadvantage
typo fixes: aquire -> acquire
typo fixes: mecanism -> mechanism
typo fixes: bandwith -> bandwidth
fix a typo in the RTC_CLASS help text
smb is no longer maintained
Manually merged trivial conflict in arch/um/kernel/vmlinux.lds.S
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Add a rq_sendfile_ok flag to svc_rqst which will be cleared in the privacy
case so that the wrapping code will get copies of the read data instead of
real page cache pages. This makes life simpler when we encrypt the response.
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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Since nfsv4 actually keeps around the file descriptors it gets from open
(instead of just using them for a single read or write operation), we need to
make sure that we can do RDWR opens and not just RDONLY/WRONLY.
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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These tests always returned true; clearly that wasn't what was intended.
In keeping with kernel style, make them functions instead of macros while
we're at it.
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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In the event that lookup_one_len() fails in nfsd_link(), fh_unlock() is
skipped and locks are held overlong.
Patch was tested on 2.6.17-rc2 by causing lookup_one_len() to fail and
verifying that fh_unlock() gets called appropriately.
Signed-off-by: David M. Richter <richterd@citi.umich.edu>
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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We're checking nfs_in_grace here a few times when there isn't really any
reason to--bad_stateid is probably the more sensible return value anyway.
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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permissions problem
In the typical v2/v3 case the only new filehandles used as arguments to
operations are filehandles taken directly off the wire, which don't get
dentries until fh_verify() is called.
But in v4 the filehandles that are arguments to operations were often created
by previous operations (putrootfh, lookup, etc.) using fh_compose, which sets
the dentry in the filehandle without calling nfsd_setuser().
This also means that, for example, if filesystem B is mounted on filesystem A,
and filesystem A is exported without root-squashing, then a client can bypass
the rootsquashing on B using a compound that starts at a filehandle in A,
crosses into B using lookups, and then does stuff in B.
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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Fix an improper unlock in an error path.
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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nfsd tries to return to a client the same sort of filehandle as was used by
the client. This removes some filehandle aliasing issues and means that a
server upgrade followed by a downgrade will not confused clients not restarted
during that time.
However when crossing a mountpoint, the filehandle used for one filesystem
doesn't provide any useful information on what sort of filehandle should be
used on the other, and can provide misleading information. So if the
reference filehandle is on a different filesystem to the one being generated,
ignore it.
Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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There is a perfectly valid situation where fh_update gets called on an already
uptodate filehandle - in nfsd_create_v3 where a CREATE_UNCHECKED finds an
existing file and wants to just set the size.
We could possible optimise out the call in that case, but the only harm
involved is that fh_update prints a warning, so it is easier to remove the
warning.
Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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Type '3' is used for the fsid in filehandles when the device number of the
device holding the filesystem has more than 8 bits in either major or minor.
Unfortunately expkey_parse doesn't recognise type 3. Fix this.
(Slighty modified from Frank's original)
Signed-off-by: Frank Filz <ffilzlnx@us.ibm.com>
Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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Just testing the i_sb isn't really enough, at least the vfsmnt must be the
same. Thanks Al.
Cc: Al Viro <viro@ftp.linux.org.uk>
Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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Add a new security hook definition for the sys_ioprio_get operation. At
present, the SELinux hook function implementation for this hook is
identical to the getscheduler implementation but a separate hook is
introduced to allow this check to be specialized in the future if
necessary.
This patch also creates a helper function get_task_ioprio which handles the
access check in addition to retrieving the ioprio value for the task.
Signed-off-by: David Quigley <dpquigl@tycho.nsa.gov>
Acked-by: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: James Morris <jmorris@namei.org>
Cc: Jens Axboe <axboe@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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The remaining counters in page_state after the zoned VM counter patches
have been applied are all just for show in /proc/vmstat. They have no
essential function for the VM.
We use a simple increment of per cpu variables. In order to avoid the most
severe races we disable preempt. Preempt does not prevent the race between
an increment and an interrupt handler incrementing the same statistics
counter. However, that race is exceedingly rare, we may only loose one
increment or so and there is no requirement (at least not in kernel) that
the vm event counters have to be accurate.
In the non preempt case this results in a simple increment for each
counter. For many architectures this will be reduced by the compiler to a
single instruction. This single instruction is atomic for i386 and x86_64.
And therefore even the rare race condition in an interrupt is avoided for
both architectures in most cases.
The patchset also adds an off switch for embedded systems that allows a
building of linux kernels without these counters.
The implementation of these counters is through inline code that hopefully
results in only a single instruction increment instruction being emitted
(i386, x86_64) or in the increment being hidden though instruction
concurrency (EPIC architectures such as ia64 can get that done).
Benefits:
- VM event counter operations usually reduce to a single inline instruction
on i386 and x86_64.
- No interrupt disable, only preempt disable for the preempt case.
Preempt disable can also be avoided by moving the counter into a spinlock.
- Handling is similar to zoned VM counters.
- Simple and easily extendable.
- Can be omitted to reduce memory use for embedded use.
References:
RFC http://marc.theaimsgroup.com/?l=linux-kernel&m=113512330605497&w=2
RFC http://marc.theaimsgroup.com/?l=linux-kernel&m=114988082814934&w=2
local_t http://marc.theaimsgroup.com/?l=linux-kernel&m=114991748606690&w=2
V2 http://marc.theaimsgroup.com/?t=115014808400007&r=1&w=2
V3 http://marc.theaimsgroup.com/?l=linux-kernel&m=115024767022346&w=2
V4 http://marc.theaimsgroup.com/?l=linux-kernel&m=115047968808926&w=2
Signed-off-by: Christoph Lameter <clameter@sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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