Getattr and lookup operations can be running in parallel to attribute changing
operations, such as write and setattr.

This means, that if for example getattr was slower than a write, the cached
size attribute could be set to a stale value.

To prevent this race, introduce a per-filesystem attribute version counter.
This counter is incremented whenever cached attributes are modified, and the
incremented value stored in the inode.

Before storing new attributes in the cache, getattr and lookup check, using
the version number, whether the attributes have been modified during the
request's lifetime.  If so, the returned attributes are not cached, because
they might be stale.

Thanks to Jakub Bogusz for the bug report and test program.

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: NMiklos Szeredi <mszeredi@suse.cz>
Cc: Jakub Bogusz <jakub.bogusz@gemius.pl>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

The following operation didn't check if sending the request was allowed:

  setattr
  listxattr
  statfs

Some other operations don't explicitly do the check, but VFS calls
->permission() which checks this.
Signed-off-by: NMiklos Szeredi <mszeredi@suse.cz>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Define a new function fuse_refresh_attributes() that conditionally refreshes
the attributes based on the validity timeout.

In fuse_permission() only refresh the attributes for checking the execute bits
if necessary.
Signed-off-by: NMiklos Szeredi <mszeredi@suse.cz>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

The VFS checks sticky bits on the parent directory even if the filesystem
defines it's own ->permission().  In some situations (sshfs, mountlo, etc) the
user does have permission to delete a file even if the attribute based
checking would not allow it.

So work around this by storing the permission bits separately and returning
them in stat(), but cutting the permission bits off from inode->i_mode.

This is slightly hackish, but it's probably not worth it to add new
infrastructure in VFS and a slight performance penalty for all filesystems,
just for the sake of fuse.

[Jan Engelhardt] cosmetic fixes
Signed-off-by: NMiklos Szeredi <mszeredi@suse.cz>
Cc: Jan Engelhardt <jengelh@linux01.gwdg.de>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

fuse_permission() didn't refresh inode attributes before using them, even if
the validity has already expired.

Thanks to Junjiro Okajima for spotting this.

Also remove some old code to unconditionally refresh the attributes on the
root inode.
Signed-off-by: NMiklos Szeredi <mszeredi@suse.cz>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Memory mappings were only truncated on an explicit truncate, but not when the
file size was changed externally.

Fix this by moving the truncation code from fuse_setattr to
fuse_change_attributes.

Yes, there are races between write and and external truncation, but we can't
really do anything about them.
Signed-off-by: NMiklos Szeredi <mszeredi@suse.cz>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Make lifetime of 'struct fuse_file' independent from 'struct file' by adding a
reference counter and destructor.

This will enable asynchronous page writeback, where it cannot be guaranteed,
that the file is not released while a request with this file handle is being
served.

The actual RELEASE request is only sent when there are no more references to
the fuse_file.
Signed-off-by: NMiklos Szeredi <mszeredi@suse.cz>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

The wrong lookup flag was tested in ->create() causing havoc (error or
Oops) when a regular file was created with mknod() in a fuse filesystem.

Thanks to J. Cameijo Cerdeira for the report.

Kernels 2.6.18 onward are affected.  Please apply to -stable as well.
Signed-off-by: NMiklos Szeredi <mszeredi@suse.cz>
Cc: <stable@kernel.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

If rootmode isn't valid, we hit the BUG() in fuse_init_inode.  Now
EINVAL is returned.
Signed-off-by: NTimo Savola <tsavola@movial.fi>
Signed-off-by: NMiklos Szeredi <mszeredi@suse.cz>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Many struct inode_operations in the kernel can be "const".  Marking them const
moves these to the .rodata section, which avoids false sharing with potential
dirty data.  In addition it'll catch accidental writes at compile time to
these shared resources.
Signed-off-by: NArjan van de Ven <arjan@linux.intel.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Signed-off-by: NJosef Sipek <jsipek@fsl.cs.sunysb.edu>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Add support for the BMAP operation for block device based filesystems.  This
is needed to support swap-files and lilo.
Signed-off-by: NMiklos Szeredi <miklos@szeredi.hu>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Remove unneeded code from fuse_dentry_revalidate().  This made some sense
while the validity time could wrap around, but now it's a very obvious no-op.
Signed-off-by: NMiklos Szeredi <miklos@szeredi.hu>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Fix bug in certain error paths of lookup routines.  The request object was
reused for sending FORGET, which is illegal.  This bug could cause an Oops
in 2.6.18.  In earlier versions it might silently corrupt memory, but this
is very unlikely.

These error paths are never triggered by libfuse, so this wasn't noticed
even with the 2.6.18 kernel, only with a filesystem using the raw kernel
interface.

Thanks to Russ Cox for the bug report and test filesystem.
Signed-off-by: NMiklos Szeredi <miklos@szeredi.hu>
Cc: <stable@kernel.org>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

There's no locking for ->d_revalidate, so fuse_dentry_revalidate() should use
dget_parent() instead of simply dereferencing ->d_parent.

Due to topology changes in the directory tree the parent could become negative
or be destroyed while being used.  There hasn't been any reports about this
yet.
Signed-off-by: NMiklos Szeredi <miklos@szeredi.hu>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Fuse considered it an error (EIO) if lookup returned a directory inode, to
which a dentry already refered.  This is because directory aliases are not
allowed.

But in a network filesystem this could happen legitimately, if a directory is
moved on a remote client.  This patch attempts to relax the restriction by
trying to first evict the offending alias from the cache.  If this fails, it
still returns an error (EBUSY).

A rarer situation is if an mkdir races with an indenpendent lookup, which
finds the newly created directory already moved.  In this situation the mkdir
should return success, but that would be incorrect, since the dentry cannot be
instantiated, so return EBUSY.

Previously checking for a directory alias and instantiation of the dentry
weren't done atomically in lookup/mkdir, hence two such calls racing with each
other could create aliased directories.  To prevent this introduce a new
per-connection mutex: fuse_conn->inst_mutex, which is taken for instantiations
with a directory inode.
Signed-off-by: NMiklos Szeredi <miklos@szeredi.hu>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

An inode could be returned by independent parallel lookups, in this case an
update of the lookup counter could be lost resulting in a memory leak in
userspace.
Signed-off-by: NMiklos Szeredi <miklos@szeredi.hu>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Fuse didn't always call i_size_write() with i_mutex held which caused rare
hangs on SMP/32bit.  This bug has been present since fuse-2.2, well before
being merged into mainline.

The simplest solution is to protect i_size_write() with the per-connection
spinlock.  Using i_mutex for this purpose would require some restructuring of
the code and I'm not even sure it's always safe to acquire i_mutex in all
places i_size needs to be set.

Since most of vmtruncate is already duplicated for other reasons, duplicate
the remaining part as well, making all i_size_write() calls internal to fuse.

Using i_size_write() was unnecessary in fuse_init_inode(), since this function
is only called on a newly created locked inode.

Reported by a few people over the years, but special thanks to Dana Henriksen
who was persistent enough in helping me debug it.
Signed-off-by: NMiklos Szeredi <miklos@szeredi.hu>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Some filesystems, instead of simply decrementing i_nlink, simply zero it
during an unlink operation.  We need to catch these in addition to the
decrement operations.
Signed-off-by: NDave Hansen <haveblue@us.ibm.com>
Acked-by: NChristoph Hellwig <hch@lst.de>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

In the "operation does permission checking" model used by fuse, chdir
permission is not checked, since there's no chdir method.

For this case set a lookup flag, which will be passed to ->permission(), so
fuse can distinguish it from permission checks for other operations.
Signed-off-by: NMiklos Szeredi <miklos@szeredi.hu>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

It is entirely possible (though rare) that jiffies half-wraps around, while a
dentry/inode remains in the cache.  This could mean that the dentry/inode is
not invalidated for another half wraparound-time.

To get around this problem, use 64-bit jiffies.  The only problem with this is
that dentry->d_time is 32 bits on 32-bit archs.  So use d_fsdata as the high
32 bits.  This is an ugly hack, but far simpler, than having to allocate
private data just for this purpose.

Since 64-bit jiffies can be assumed never to wrap around, simple comparison
can be used, and a zero time value can represent "invalid".
Signed-off-by: NMiklos Szeredi <miklos@szeredi.hu>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

An attribute and entry timeout of zero should mean, that the entity is
invalidated immediately after the operation.  Previously invalidation only
happened at the next clock tick.

Reported and tested by Craig Davies.
Signed-off-by: NMiklos Szeredi <miklos@szeredi.hu>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Don't put requests into the background when a fatal interrupt occurs while the
request is in userspace.  This removes a major wart from the implementation.

Backgrounding of requests was introduced to allow breaking of deadlocks.
However now the same can be achieved by aborting the filesystem through the
'abort' sysfs attribute.

This is a change in the interface, but should not cause problems, since these
kinds of deadlocks never happen during normal operation.
Signed-off-by: NMiklos Szeredi <miklos@szeredi.hu>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

FUSE allocated most requests from a fixed size pool filled at mount time.
However in some cases (release/forget) non-pool requests were used.  File
locking operations aren't well served by the request pool, since they may
block indefinetly thus exhausting the pool.

This patch removes the request pool and always allocates requests on demand.
Signed-off-by: NMiklos Szeredi <miklos@szeredi.hu>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

This is a conversion to make the various file_operations structs in fs/
const.  Basically a regexp job, with a few manual fixups

The goal is both to increase correctness (harder to accidentally write to
shared datastructures) and reducing the false sharing of cachelines with
things that get dirty in .data (while .rodata is nicely read only and thus
cache clean)
Signed-off-by: NArjan van de Ven <arjan@infradead.org>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

If negative entries (nodeid == 0) were sent in reply to LOOKUP requests,
two bugs could be triggered:

- looking up a negative entry would return -EIO,

- revaildate on an entry which turned negative would send a FORGET
  request with zero nodeid, which would cause an abort() in the
  library.

The above would only happen if the 'negative_timeout=N' option was used,
otherwise lookups reply -ENOENT, which worked correctly.
Signed-off-by: NMiklos Szeredi <miklos@szeredi.hu>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Add a separate function for filling in the READ request.  This will make it
possible to send asynchronous READ requests as well as synchronous ones.
Signed-off-by: NMiklos Szeredi <miklos@szeredi.hu>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Inline keyword is unnecessary in most cases.  Clean them up.
Signed-off-by: NMiklos Szeredi <miklos@szeredi.hu>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Previously invalid types were quietly changed to regular files, but at
revalidation the inode was changed to bad.  This was rather inconsistent
behavior.

Now check if the type is valid on initial lookup, and return -EIO if not.
Signed-off-by: NMiklos Szeredi <miklos@szeredi.hu>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Change the way a too large request is handled.  Until now in this case the
device read returned -EINVAL and the operation returned -EIO.

Make it more flexibible by not returning -EINVAL from the read, but restarting
it instead.

Also remove the fixed limit on setxattr data and let the filesystem provide as
large a read buffer as it needs to handle the extended attribute data.

The symbolic link length is already checked by VFS to be less than PATH_MAX,
so the extra check against FUSE_SYMLINK_MAX is not needed.

The check in fuse_create_open() against FUSE_NAME_MAX is not needed, since the
dentry has already been looked up, and hence the name already checked.
Signed-off-by: NMiklos Szeredi <miklos@szeredi.hu>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Make file operations on a bad inode fail.  This just makes things a
bit more consistent.
Signed-off-by: NMiklos Szeredi <miklos@szeredi.hu>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Document some not-so-trivial functions.
Signed-off-by: NMiklos Szeredi <miklos@szeredi.hu>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Add support for caching negative dentries.

Up till now, ->d_revalidate() always forced a new lookup on these.  Now let
the lookup method return a zero node ID (not used for anything else) meaning a
negative entry, but with a positive cache timeout.  The old way of signaling
negative entry (replying ENOENT) still works.

Userspace should check the ABI minor version to see whether sending a zero ID
is allowed by the kernel or not.
Signed-off-by: NMiklos Szeredi <miklos@szeredi.hu>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Simplify fuse_lookup() and related functions.
Signed-off-by: NMiklos Szeredi <miklos@szeredi.hu>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Check for invalid node ID values in the new atomic create+open method.
Signed-off-by: NMiklos Szeredi <miklos@szeredi.hu>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Check the created directory inode for aliases in the mkdir() method.
Signed-off-by: NMiklos Szeredi <miklos@szeredi.hu>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

This patch passes the file handle supplied in iattr to userspace, in case the
->setattr() was invoked from sys_ftruncate().  This solves the permission
checking (or lack thereof) in ftruncate() for the class of filesystems served
by an unprivileged userspace process.
Signed-off-by: NMiklos Szeredi <miklos@szeredi.hu>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

This patch adds an atomic create+open operation.  This does not yet work if
the file type changes between lookup and create+open, but solves the
permission checking problems for the separte create and open methods.
Signed-off-by: NMiklos Szeredi <miklos@szeredi.hu>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Add a new access call, which will only be called if ->permission is invoked
from sys_access().  In all other cases permission checking is delayed until
the actual filesystem operation.
Signed-off-by: NMiklos Szeredi <miklos@szeredi.hu>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

The -EROFS check has moved up to permission() in the VFS a while ago.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Acked-by: NMiklos Szeredi <miklos@szeredi.hu>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>