Messages in this thread Patch in this message | | | Date | Mon, 20 Nov 2006 13:18:38 -0500 | From | Mathieu Desnoyers <> | Subject | Debugfs : inotify, multiple calls to debugfs_create_file, remove |
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Hi Greg,
I just had to add inotify support to my LTTng consumer so I could inform it of the presence of new CPUs (for CPU hotplug). I noticed that no notification event was being sent when a debugfs file is created from within the kernel through debugfs_create. There are probably other notifications missing, but here is the patch adding the one I care about. Should it be added in libfs or in debugfs ?
A second problem I noticed is when a caller calls debugfs_create_file more than once : the result is that the debugfs_remove will fail. I guess the second call to debugfs_create_file increments the reference counts (there is not fix for this issue in my patch).
Third problem : a failing call to debugfs_remove keeps the filesystem pinned. (fixed by calling simple_release_fs in the error path).
The third problem : When a process is in a directory, the call to simple_rmdir will fail. Debugfs does not use its return value. I noticed that calling simple_unlink on a directory when simple_rmdir fails removes the directory that would otherwise be left there. I am not sure if this approach is correct through.
This patch is against Linux 2.6.18.
Regards,
Mathieu
diff --git a/fs/debugfs/inode.c b/fs/debugfs/inode.c index e8ae304..d88203f 100644 --- a/fs/debugfs/inode.c +++ b/fs/debugfs/inode.c @@ -23,6 +23,7 @@ #include <linux/pagemap.h> #include <linux/init.h> #include <linux/namei.h> #include <linux/debugfs.h> +#include <linux/fsnotify.h> #define DEBUGFS_MAGIC 0x64626720 @@ -156,7 +157,8 @@ static int debugfs_create_by_name(const } else error = PTR_ERR(dentry); mutex_unlock(&parent->d_inode->i_mutex); - + if (!error) + fsnotify_create(parent->d_inode, *dentry); return error; } @@ -204,7 +206,10 @@ struct dentry *debugfs_create_file(const error = debugfs_create_by_name(name, mode, parent, &dentry); if (error) { + /* FIXME : a failing call to debugfs_create_file leaves a + * stalled entry after a remove. */ dentry = NULL; + simple_release_fs(&debugfs_mount, &debugfs_mount_count); goto exit; } @@ -265,6 +270,7 @@ EXPORT_SYMBOL_GPL(debugfs_create_dir); void debugfs_remove(struct dentry *dentry) { struct dentry *parent; + int ret = 0; if (!dentry) return; @@ -277,8 +283,12 @@ void debugfs_remove(struct dentry *dentr if (debugfs_positive(dentry)) { if (dentry->d_inode) { if (S_ISDIR(dentry->d_inode->i_mode)) - simple_rmdir(parent->d_inode, dentry); + ret = simple_rmdir(parent->d_inode, dentry); else + ret = simple_unlink(parent->d_inode, dentry); + /* simple_rmdir failed because the directory + * is used. Force deletion. */ + if (ret) simple_unlink(parent->d_inode, dentry); dput(dentry); } OpenPGP public key: http://krystal.dyndns.org:8080/key/compudj.gpg Key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68 - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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