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>
The situation: VFS inode X on a mounted ntfs volume is dirty. For
same inode X, the ntfs_inode is dirty and thus corresponding on-disk
inode, i.e. mft record, which is in a dirty PAGE_CACHE_PAGE belonging
to the table of inodes, i.e. $MFT, inode 0.
What happens:
Process 1: sys_sync()/umount()/whatever... calls
__sync_single_inode() for $MFT -> do_writepages() -> write_page for
the dirty page containing the on-disk inode X, the page is now locked
-> ntfs_write_mst_block() which clears PageUptodate() on the page to
prevent anyone else getting hold of it whilst it does the write out.
This is necessary as the on-disk inode needs "fixups" applied before
the write to disk which are removed again after the write and
PageUptodate is then set again. It then analyses the page looking
for dirty on-disk inodes and when it finds one it calls
ntfs_may_write_mft_record() to see if it is safe to write this
on-disk inode. This then calls ilookup5() to check if the
corresponding VFS inode is in icache(). This in turn calls ifind()
which waits on the inode lock via wait_on_inode whilst holding the
global inode_lock.
Process 2: pdflush results in a call to __sync_single_inode for the
same VFS inode X on the ntfs volume. This locks the inode (I_LOCK)
then calls write-inode -> ntfs_write_inode -> map_mft_record() ->
read_cache_page() for the page (in page cache of table of inodes
$MFT, inode 0) containing the on-disk inode. This page has
PageUptodate() clear because of Process 1 (see above) so
read_cache_page() blocks when it tries to take the page lock for the
page so it can call ntfs_read_page().
Thus Process 1 is holding the page lock on the page containing the
on-disk inode X and it is waiting on the inode X to be unlocked in
ifind() so it can write the page out and then unlock the page.
And Process 2 is holding the inode lock on inode X and is waiting for
the page to be unlocked so it can call ntfs_readpage() or discover
that Process 1 set PageUptodate() again and use the page.
Thus we have a deadlock due to ifind() waiting on the inode lock.
The solution: The fix is to use the newly introduced
ilookup5_nowait() which does not wait on the inode's lock and hence
avoids the deadlock. This is safe as we do not care about the VFS
inode and only use the fact that it is in the VFS inode cache and the
fact that the vfs and ntfs inodes are one struct in memory to find
the ntfs inode in memory if present. Also, the ntfs inode has its
own locking so it does not matter if the vfs inode is locked.
Signed-off-by: Anton Altaparmakov <aia21@cantab.net>
The current isofs treatment of hidden files is flawed in two ways. First,
it does not provide sufficient granularity; it hides both 'hidden' files
and 'associated' files (resource fork for Mac files). Second, the default
behavior to completely strip hidden files, while an admirable
implementation of the spec, is a poor choice given the real world use of
hidden files as a poor mans copy protection scheme for MSDOS and Windows
based systems. A longer description of this is available here:
http://www.uwsg.iu.edu/hypermail/linux/kernel/0205.3/0267.html
This patch was originally built after a few private conversations with Alan
Cox; I shamefully failed to persist in seeing it go forward, I hope to make
amends now.
This patch introduces granularity by allowing explicit control for both
hidden and associated files. It also reverses the default so that by
default, hidden files are treated as regular files on the iso9660 file
system.
This allow Wine to process Windows CDs, including those that are hybrid
Mac/Windows CDs properly and completely, without our having to go muck up
peoples fstabs as we do now. (I have tested this with such a hybrid +
hidden CD and have verified that this patch works as claimed).
Signed-off-by: Jeremy White <jwhite@codeweavers.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
To improve shmem scalability, we allowed tmpfs instances which don't need
their blocks or inodes limited not to count them, and not to allocate any
sbinfo. Which was okay when the only use for the sbinfo was accounting
blocks and inodes; but since then a couple of unrelated projects extending
tmpfs want to store other data in the sbinfo. Whether either extension
reaches mainline is beside the point: I'm guilty of a bad design decision,
and should restore sbinfo to make any such future extensions easier.
So, once again allocate a shmem_sb_info for every shmem/tmpfs instance, and
now let max_blocks 0 indicate unlimited blocks, and max_inodes 0 unlimited
inodes. Brent Casavant verified (many months ago) that this does not
perceptibly impact the scalability (since the unlimited sbinfo cacheline is
repeatedly accessed but only once dirtied).
And merge shmem_set_size into its sole caller shmem_remount_fs.
Signed-off-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
The driver model has a "detach_state" mechanism that:
- Has never been used by any in-kernel drive;
- Is superfluous, since driver remove() methods can do the same thing;
- Became buggy when the suspend() parameter changed semantics and type;
- Could self-deadlock when called from certain suspend contexts;
- Is effectively wasted documentation, object code, and headspace.
This removes that "detach_state" mechanism; net code shrink, as well
as a per-device saving in the driver model and sysfs.
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
enable bit which is set appropriately and a per inode sparse disable
bit which is preset on some system file inodes as appropriate.
- Enforce that sparse support is disabled on NTFS volumes pre 3.0.
Signed-off-by: Anton Altaparmakov <aia21@cantab.net>
The patch updates the documentation for /proc. super-nr and super-max have
been dropped from the kernel since 2.4.9 due to minor numbering issues.
This change was not documented in the documentation.
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.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!
