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* Fix inotify watch removal/umount racesAl Viro2008-11-15
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Inotify watch removals suck violently. To kick the watch out we need (in this order) inode->inotify_mutex and ih->mutex. That's fine if we have a hold on inode; however, for all other cases we need to make damn sure we don't race with umount. We can *NOT* just grab a reference to a watch - inotify_unmount_inodes() will happily sail past it and we'll end with reference to inode potentially outliving its superblock. Ideally we just want to grab an active reference to superblock if we can; that will make sure we won't go into inotify_umount_inodes() until we are done. Cleanup is just deactivate_super(). However, that leaves a messy case - what if we *are* racing with umount() and active references to superblock can't be acquired anymore? We can bump ->s_count, grab ->s_umount, which will almost certainly wait until the superblock is shut down and the watch in question is pining for fjords. That's fine, but there is a problem - we might have hit the window between ->s_active getting to 0 / ->s_count - below S_BIAS (i.e. the moment when superblock is past the point of no return and is heading for shutdown) and the moment when deactivate_super() acquires ->s_umount. We could just do drop_super() yield() and retry, but that's rather antisocial and this stuff is luser-triggerable. OTOH, having grabbed ->s_umount and having found that we'd got there first (i.e. that ->s_root is non-NULL) we know that we won't race with inotify_umount_inodes(). So we could grab a reference to watch and do the rest as above, just with drop_super() instead of deactivate_super(), right? Wrong. We had to drop ih->mutex before we could grab ->s_umount. So the watch could've been gone already. That still can be dealt with - we need to save watch->wd, do idr_find() and compare its result with our pointer. If they match, we either have the damn thing still alive or we'd lost not one but two races at once, the watch had been killed and a new one got created with the same ->wd at the same address. That couldn't have happened in inotify_destroy(), but inotify_rm_wd() could run into that. Still, "new one got created" is not a problem - we have every right to kill it or leave it alone, whatever's more convenient. So we can use idr_find(...) == watch && watch->inode->i_sb == sb as "grab it and kill it" check. If it's been our original watch, we are fine, if it's a newcomer - nevermind, just pretend that we'd won the race and kill the fscker anyway; we are safe since we know that its superblock won't be going away. And yes, this is far beyond mere "not very pretty"; so's the entire concept of inotify to start with. Signed-off-by: Al Viro <viro@zeniv.linux.org.uk> Acked-by: Greg KH <greg@kroah.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* flag parameters: NONBLOCK in inotify_initUlrich Drepper2008-07-24
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | This patch adds non-blocking support for inotify_init1. The additional changes needed are minimal. The following test must be adjusted for architectures other than x86 and x86-64 and in case the syscall numbers changed. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ #include <fcntl.h> #include <stdio.h> #include <unistd.h> #include <sys/syscall.h> #ifndef __NR_inotify_init1 # ifdef __x86_64__ # define __NR_inotify_init1 294 # elif defined __i386__ # define __NR_inotify_init1 332 # else # error "need __NR_inotify_init1" # endif #endif #define IN_NONBLOCK O_NONBLOCK int main (void) { int fd = syscall (__NR_inotify_init1, 0); if (fd == -1) { puts ("inotify_init1(0) failed"); return 1; } int fl = fcntl (fd, F_GETFL); if (fl == -1) { puts ("fcntl failed"); return 1; } if (fl & O_NONBLOCK) { puts ("inotify_init1(0) set non-blocking mode"); return 1; } close (fd); fd = syscall (__NR_inotify_init1, IN_NONBLOCK); if (fd == -1) { puts ("inotify_init1(IN_NONBLOCK) failed"); return 1; } fl = fcntl (fd, F_GETFL); if (fl == -1) { puts ("fcntl failed"); return 1; } if ((fl & O_NONBLOCK) == 0) { puts ("inotify_init1(IN_NONBLOCK) set non-blocking mode"); return 1; } close (fd); puts ("OK"); return 0; } ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Signed-off-by: Ulrich Drepper <drepper@redhat.com> Acked-by: Davide Libenzi <davidel@xmailserver.org> Cc: Michael Kerrisk <mtk.manpages@googlemail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* flag parameters: inotify_initUlrich Drepper2008-07-24
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | This patch introduces the new syscall inotify_init1 (note: the 1 stands for the one parameter the syscall takes, as opposed to no parameter before). The values accepted for this parameter are function-specific and defined in the inotify.h header. Here the values must match the O_* flags, though. In this patch CLOEXEC support is introduced. The following test must be adjusted for architectures other than x86 and x86-64 and in case the syscall numbers changed. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ #include <fcntl.h> #include <stdio.h> #include <unistd.h> #include <sys/syscall.h> #ifndef __NR_inotify_init1 # ifdef __x86_64__ # define __NR_inotify_init1 294 # elif defined __i386__ # define __NR_inotify_init1 332 # else # error "need __NR_inotify_init1" # endif #endif #define IN_CLOEXEC O_CLOEXEC int main (void) { int fd; fd = syscall (__NR_inotify_init1, 0); if (fd == -1) { puts ("inotify_init1(0) failed"); return 1; } int coe = fcntl (fd, F_GETFD); if (coe == -1) { puts ("fcntl failed"); return 1; } if (coe & FD_CLOEXEC) { puts ("inotify_init1(0) set close-on-exit"); return 1; } close (fd); fd = syscall (__NR_inotify_init1, IN_CLOEXEC); if (fd == -1) { puts ("inotify_init1(IN_CLOEXEC) failed"); return 1; } coe = fcntl (fd, F_GETFD); if (coe == -1) { puts ("fcntl failed"); return 1; } if ((coe & FD_CLOEXEC) == 0) { puts ("inotify_init1(O_CLOEXEC) does not set close-on-exit"); return 1; } close (fd); puts ("OK"); return 0; } ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ [akpm@linux-foundation.org: add sys_ni stub] Signed-off-by: Ulrich Drepper <drepper@redhat.com> Acked-by: Davide Libenzi <davidel@xmailserver.org> Cc: Michael Kerrisk <mtk.manpages@googlemail.com> Cc: <linux-arch@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* [PATCH] new helper - inotify_evict_watch()Al Viro2007-10-21
| | | | | | Kicks the watch out without dropping it. Called under ->inotify_mutex Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* [PATCH] new helper - inotify_clone_watch()Al Viro2007-10-21
| | | | Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* [PATCH] inotify (4/5): allow watch removal from event handlerAmy Griffis2006-06-20
| | | | | | | | | | | | Allow callers to remove watches from their event handler via inotify_remove_watch_locked(). This functionality can be used to achieve IN_ONESHOT-like functionality for a subset of events in the mask. Signed-off-by: Amy Griffis <amy.griffis@hp.com> Acked-by: Robert Love <rml@novell.com> Acked-by: John McCutchan <john@johnmccutchan.com> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* [PATCH] inotify (3/5): add interfaces to kernel APIAmy Griffis2006-06-20
| | | | | | | | | | | | | | | | | Add inotify_init_watch() so caller can use inotify_watch refcounts before calling inotify_add_watch(). Add inotify_find_watch() to find an existing watch for an (ih,inode) pair. This is similar to inotify_find_update_watch(), but does not update the watch's mask if one is found. Add inotify_rm_watch() to remove a watch via the watch pointer instead of the watch descriptor. Signed-off-by: Amy Griffis <amy.griffis@hp.com> Acked-by: Robert Love <rml@novell.com> Acked-by: John McCutchan <john@johnmccutchan.com> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* [PATCH] inotify (2/5): add name's inode to event handlerAmy Griffis2006-06-20
| | | | | | | | | | When an inotify event includes a dentry name, also include the inode associated with that name. Signed-off-by: Amy Griffis <amy.griffis@hp.com> Acked-by: Robert Love <rml@novell.com> Acked-by: John McCutchan <john@johnmccutchan.com> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* [PATCH] inotify (1/5): split kernel API from userspace supportAmy Griffis2006-06-20
| | | | | | | | | | | | | | | | The following series of patches introduces a kernel API for inotify, making it possible for kernel modules to benefit from inotify's mechanism for watching inodes. With these patches, inotify will maintain for each caller a list of watches (via an embedded struct inotify_watch), where each inotify_watch is associated with a corresponding struct inode. The caller registers an event handler and specifies for which filesystem events their event handler should be called per inotify_watch. Signed-off-by: Amy Griffis <amy.griffis@hp.com> Acked-by: Robert Love <rml@novell.com> Acked-by: John McCutchan <john@johnmccutchan.com> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* [PATCH] remove config.h from inotify.hAl Viro2006-06-20
| | | | Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* [PATCH] inotify: lock avoidance with parent watch status in dentryNick Piggin2006-03-25
| | | | | | | | | | | | | | | | | | | | | | Previous inotify work avoidance is good when inotify is completely unused, but it breaks down if even a single watch is in place anywhere in the system. Robin Holt notices that udev is one such culprit - it slows down a 512-thread application on a 512 CPU system from 6 seconds to 22 minutes. Solve this by adding a flag in the dentry that tells inotify whether or not its parent inode has a watch on it. Event queueing to parent will skip taking locks if this flag is cleared. Setting and clearing of this flag on all child dentries versus event delivery: this is no in terms of race cases, and that was shown to be equivalent to always performing the check. The essential behaviour is that activity occuring _after_ a watch has been added and _before_ it has been removed, will generate events. Signed-off-by: Nick Piggin <npiggin@suse.de> Cc: Robert Love <rml@novell.com> Cc: John McCutchan <ttb@tentacle.dhs.org> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] inotify: add two inotify_add_watch flagsJohn McCutchan2005-12-12
| | | | | | | | | | | | | | | | | | | | | The below patch lets userspace have more control over the inodes that inotify will watch. It introduces two new flags. IN_ONLYDIR -- only watch the inode if it is a directory. This is needed to avoid the race that can occur when we want to be sure that we are watching a directory. IN_DONT_FOLLOW -- don't follow a symlink. In combination with IN_ONLYDIR we can make sure that we don't watch the target of symlinks. The issues the flags fix came up when writing the gnome-vfs inotify backend. Default behaviour is unchanged. Signed-off-by: John McCutchan <ttb@tentacle.dhs.org> Acked-by: Robert Love <rml@novell.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] inotify: fix event loss on hardlinked filesJohn McCutchan2005-09-07
| | | | | | | | | | | | | | | | People have run into a problem when they do this: watch (file1, all_events); watch (file2, some_events); if file2 is a hard link to file1, some events will be missed because by default we replace the mask. The patch below adds a flag IN_MASK_ADD which will cause inotify to add to the existing mask if present. Signed-off-by: John McCutchan <ttb@tentacle.dhs.org> Signed-off-by: Robert Love <rml@novell.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] inotify: add MOVE_SELF eventJohn McCutchan2005-08-15
| | | | | | | | | | | | | | | | | | | | | This adds a MOVE_SELF event to inotify. It is sent whenever the inode you are watching is moved. We need this event so that we can catch something like this: - app1: watch /etc/mtab - app2: cp /etc/mtab /tmp/mtab-work mv /etc/mtab /etc/mtab~ mv /tmp/mtab-work /etc/mtab app1 still thinks it's watching /etc/mtab but it's actually watching /etc/mtab~. Signed-off-by: John McCutchan <ttb@tentacle.dhs.org> Signed-off-by: Robert Love <rml@novell.com> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
* [PATCH] inotifyRobert Love2005-07-12
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>