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vfs: introduce FMODE_NONOTIFY

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This is a new f_mode which can only be set by the kernel.  It indicates
that the fd was opened by fanotify and should not cause future fanotify
events.  This is needed to prevent fanotify livelock.  An example of
obvious livelock is from fanotify close events.

Process A closes file1
This creates a close event for file1.
fanotify opens file1 for Listener X
Listener X deals with the event and closes its fd for file1.
This creates a close event for file1.
fanotify opens file1 for Listener X
Listener X deals with the event and closes its fd for file1.
This creates a close event for file1.
fanotify opens file1 for Listener X
Listener X deals with the event and closes its fd for file1.
notice a pattern?

The fix is to add the FMODE_NONOTIFY bit to the open filp done by the kernel
for fanotify.  Thus when that file is used it will not generate future
events.

This patch simply defines the bit.

Signed-off-by: Eric Paris <eparis@redhat.com>
This commit is contained in:
Eric Paris 2009-12-17 21:24:25 -05:00
parent 3556608709
commit ecf081d1a7
3 changed files with 29 additions and 9 deletions
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24
include/linux/fsnotify.h
View file

@ -165,8 +165,10 @@ static inline void fsnotify_access(struct file *file)
if (S_ISDIR(inode->i_mode))
mask |= FS_IN_ISDIR;
fsnotify_parent(path, NULL, mask);
fsnotify(inode, mask, path, FSNOTIFY_EVENT_PATH, NULL, 0);
if (!(file->f_mode & FMODE_NONOTIFY)) {
fsnotify_parent(path, NULL, mask);
fsnotify(inode, mask, path, FSNOTIFY_EVENT_PATH, NULL, 0);
}
}
/*
@ -181,8 +183,10 @@ static inline void fsnotify_modify(struct file *file)
if (S_ISDIR(inode->i_mode))
mask |= FS_IN_ISDIR;
fsnotify_parent(path, NULL, mask);
fsnotify(inode, mask, path, FSNOTIFY_EVENT_PATH, NULL, 0);
if (!(file->f_mode & FMODE_NONOTIFY)) {
fsnotify_parent(path, NULL, mask);
fsnotify(inode, mask, path, FSNOTIFY_EVENT_PATH, NULL, 0);
}
}
/*
@ -197,8 +201,10 @@ static inline void fsnotify_open(struct file *file)
if (S_ISDIR(inode->i_mode))
mask |= FS_IN_ISDIR;
fsnotify_parent(path, NULL, mask);
fsnotify(inode, mask, path, FSNOTIFY_EVENT_PATH, NULL, 0);
if (!(file->f_mode & FMODE_NONOTIFY)) {
fsnotify_parent(path, NULL, mask);
fsnotify(inode, mask, path, FSNOTIFY_EVENT_PATH, NULL, 0);
}
}
/*
@ -214,8 +220,10 @@ static inline void fsnotify_close(struct file *file)
if (S_ISDIR(inode->i_mode))
mask |= FS_IN_ISDIR;
fsnotify_parent(path, NULL, mask);
fsnotify(inode, mask, path, FSNOTIFY_EVENT_PATH, NULL, 0);
if (!(file->f_mode & FMODE_NONOTIFY)) {
fsnotify_parent(path, NULL, mask);
fsnotify(inode, mask, path, FSNOTIFY_EVENT_PATH, NULL, 0);
}
}
/*