inotify is intended to correct the deficiencies of dnotify, particularly
its inability to scale and its terrible user interface:
* dnotify requires the opening of one fd per each directory
that you intend to watch. This quickly results in too many
open files and pins removable media, preventing unmount.
* dnotify is directory-based. You only learn about changes to
directories. Sure, a change to a file in a directory affects
the directory, but you are then forced to keep a cache of
stat structures.
* dnotify's interface to user-space is awful. Signals?
inotify provides a more usable, simple, powerful solution to file change
notification:
* inotify's interface is a system call that returns a fd, not SIGIO.
You get a single fd, which is select()-able.
* inotify has an event that says "the filesystem that the item
you were watching is on was unmounted."
* inotify can watch directories or files.
Inotify is currently used by Beagle (a desktop search infrastructure),
Gamin (a FAM replacement), and other projects.
See Documentation/filesystems/inotify.txt.
Signed-off-by: Robert Love <rml@novell.com>
Cc: John McCutchan <ttb@tentacle.dhs.org>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This patch renames _mntput() to something a little more descriptive:
mntput_no_expire().
Signed-off-by: Miklos Szeredi <miklos@szeredi.hu>
Acked-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
In a duplicate of lookup_create in the af_unix code Al commented what's
going on nicely, so let's bring that over to lookup_create before the copy
is going away (I'll send a patch soon)
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
__do_follow_link() passes potentially worng vfsmount to touch_atime(). It
matters only in (currently impossible) case of symlink mounted on something,
but it's trivial to fix and that actually makes more sense.
Signed-off-by: Al Viro <viro@parcelfarce.linux.theplanet.co.uk>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Conditional mntput() moved into __do_follow_link(). There it collapses with
unconditional mntget() on the same sucker, closing another too-early-mntput()
race.
Signed-off-by: Al Viro <viro@parcelfarce.linux.theplanet.co.uk>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Getting rid of sloppy logics:
a) in do_follow_link() we have the wrong vfsmount dropped if our symlink
had been mounted on something. Currently it worls only because we never
get such situation (modulo filesystem playing dirty tricks on us). And
it obfuscates already convoluted logics...
b) same goes for open_namei().
c) in __link_path_walk() we have another "it should never happen" sloppiness -
out_dput: there does double-free on underlying vfsmount and leaks the covering
one if we hit it just after crossing a mountpoint. Again, wrong vfsmount
getting dropped.
d) another too-early-mntput() race - in do_follow_mount() we need to postpone
conditional mntput(path->mnt) until after dput(path->dentry). Again, this one
happens only in it-currently-never-happens-unless-some-fs-plays-dirty
scenario...
Signed-off-by: Al Viro <viro@parcelfarce.linux.theplanet.co.uk>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
shifted conditional mntput() into do_follow_link() - all callers were doing
the same thing.
Obviously equivalent transformation.
Signed-off-by: Al Viro <viro@parcelfarce.linux.theplanet.co.uk>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
In open_namei() exit_dput: we have mntput() done in the wrong order -
if nd->mnt != path.mnt we end up doing
mntput(nd->mnt);
nd->mnt = path.mnt;
dput(nd->dentry);
mntput(nd->mnt);
which drops nd->dentry too late. Fixed by having path.mnt go first.
That allows to switch O_NOFOLLOW under if (__follow_mount(...)) back
to exit_dput, while we are at it.
Fix for early-mntput() race + equivalent transformation.
Signed-off-by: Al Viro <viro@parcelfarce.linux.theplanet.co.uk>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
In open_namei() we take mntput(nd->mnt);nd->mnt=path.mnt; out of the if
(__follow_mount(...)), making it conditional on nd->mnt != path.mnt instead.
Then we shift the result downstream.
Equivalent transformations.
Signed-off-by: Al Viro <viro@parcelfarce.linux.theplanet.co.uk>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
In open_namei(), __follow_down() loop turned into __follow_mount().
Instead of
if we are on a mountpoint dentry
if O_NOFOLLOW checks fail
drop path.dentry
drop nd
return
do equivalent of follow_mount(&path.mnt, &path.dentry)
nd->mnt = path.mnt
we do
if __follow_mount(path) had, indeed, traversed mountpoint
/* now both nd->mnt and path.mnt are pinned down */
if O_NOFOLLOW checks fail
drop path.dentry
drop path.mnt
drop nd
return
mntput(nd->mnt)
nd->mnt = path.mnt
Now __follow_down() can be folded into follow_down() - no other callers left.
We need to reorder dput()/mntput() there - same problem as in follow_mount().
Equivalent transformation + fix for a bug in O_NOFOLLOW handling - we used to
get -ELOOP if we had the same fs mounted on /foo and /bar, had something bound
on /bar/baz and tried to open /foo/baz with O_NOFOLLOW. And fix of
too-early-mntput() race in follow_down()
Signed-off-by: Al Viro <viro@parcelfarce.linux.theplanet.co.uk>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
New helper: __follow_mount(struct path *path). Same as follow_mount(), except
that we do *not* do mntput() after the first lookup_mnt().
IOW, original path->mnt stays pinned down. We also take care to do dput()
before mntput() in the loop body (follow_mount() also needs that reordering,
but that will be done later in the series).
The following are equivalent, assuming that path.mnt == x:
(1)
follow_mount(&path.mnt, &path.dentry)
(2)
__follow_mount(&path);
if (path->mnt != x)
mntput(x);
(3)
if (__follow_mount(&path))
mntput(x);
Callers of follow_mount() in __link_path_walk() converted to (2).
Equivalent transformation + fix for too-late-mntput() race in __follow_mount()
loop.
Signed-off-by: Al Viro <viro@parcelfarce.linux.theplanet.co.uk>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
In open_namei() we never use path.mnt or path.dentry after exit: or ok:.
Assignment of path.dentry in case of LAST_BIND is dead code and only
obfuscates already convoluted function; assignment of path.mnt after
__do_follow_link() can be moved down to the place where we set path.dentry.
Obviously equivalent transformations, just to clean the air a bit in that
region.
Signed-off-by: Al Viro <viro@parcelfarce.linux.theplanet.co.uk>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
The first argument of __do_follow_link() switched to struct path *
(__do_follow_link(path->dentry, ...) -> __do_follow_link(path, ...)).
All callers have the same calls of mntget() right before and dput()/mntput()
right after __do_follow_link(); these calls have been moved inside.
Obviously equivalent transformations.
Signed-off-by: Al Viro <viro@parcelfarce.linux.theplanet.co.uk>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
mntget(path->mnt) in do_follow_link() moved down to right before the
__do_follow_link() call and rigth after loop: resp.
dput()+mntput() on non-ELOOP branch moved up to right after __do_follow_link()
call.
resulting
loop:
mntget(path->mnt);
path_release(nd);
dput(path->mnt);
mntput(path->mnt);
replaced with equivalent
dput(path->mnt);
path_release(nd);
Equivalent transformations - the reason why we have that mntget() is that
__do_follow_link() can drop a reference to nd->mnt and that's what holds
path->mnt. So that call can happen at any point prior to __do_follow_link()
touching nd->mnt. The rest is obvious.
NOTE: current tree relies on symlinks *never* being mounted on anything. It's
not hard to get rid of that assumption (actually, that will come for free
later in the series). For now we are just not making the situation worse than
it is.
Signed-off-by: Al Viro <viro@parcelfarce.linux.theplanet.co.uk>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
fix for too early mntput() in open_namei() - we pin path.mnt down for the
duration of __do_follow_link(). Otherwise we could get the fs where our
symlink lived unmounted while we were in __do_follow_link(). That would end
up with dentry of symlink staying pinned down through the fs shutdown.
Signed-off-by: Al Viro <viro@parcelfarce.linux.theplanet.co.uk>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
path.mnt in open_namei() set to mirror nd->mnt.
nd->mnt is set in 3 places in that function - path_lookup() in the beginning,
__follow_down() loop after do_last: and __do_follow_link() call after
do_link:.
We set path.mnt to nd->mnt after path_lookup() and __do_follow_link(). In
__follow_down() loop we use &path.mnt instead of &nd->mnt and set nd->mnt to
path.mnt immediately after that loop.
Obviously equivalent transformation.
Signed-off-by: Al Viro <viro@parcelfarce.linux.theplanet.co.uk>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Replaced struct dentry *dentry in namei with struct path path. All uses of
dentry replaced with path.dentry there.
Obviously equivalent transformation.
Signed-off-by: Al Viro <viro@parcelfarce.linux.theplanet.co.uk>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
All callers of do_follow_link() do mntget() right before it and
dput()+mntput() right after. These calls are moved inside do_follow_link()
now.
Obviously equivalent transformation.
Signed-off-by: Al Viro <viro@parcelfarce.linux.theplanet.co.uk>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
OK, here comes a patch series that hopefully should close all
too-early-mntput() races in fs/namei.c. Entire area is convoluted as hell, so
I'm splitting that series into _very_ small chunks.
Patches alread in the tree close only (very wide) races in following symlinks
(see "busy inodes after umount" thread some time ago). Unfortunately, quite a
few narrower races of the same nature were not closed. Hopefully this should
take care of all of them.
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
currently it opencodes it, but that's in the way of chaning the
lookup_hash interface.
I'd prefer to disallow modular af_unix over exporting lookup_create,
but I'll leave that to you.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: David S. Miller <davem@davemloft.net>
This patch makes some needlessly global identifiers static.
Signed-off-by: Adrian Bunk <bunk@stusta.de>
Acked-by: Arjan van de Ven <arjanv@infradead.org>
Acked-by: Trond Myklebust <trond.myklebust@fys.uio.no>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Main change is in path_lookup: added a goto to do audit_inode
instead of return statement, when emul_lookup_dentry for root
is successful.The existing code does audit_inode only when
lookup is done in normal root or cwd.
Other changes: Some lookup routines are returning zero on success,
and some are returning zero on failure. I documented the related
function signatures in this code path, so that one can glance over
abstract functions without understanding the entire code.
Signed-off-by: Prasanna Meda <pmeda@akamai.com>
Signed-off-by: David Woodhouse <dwmw2@infradead.org>
Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.
Let it rip!
Robert Love