Re: [PATCH] prune_icache_sb

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Russell Cattelan wrote:
Wendy Cheng wrote:

Linux kernel, particularly the VFS layer, is starting to show signs of inadequacy as the software components built upon it keep growing. I have doubts that it can keep up and handle this complexity with a development policy like you just described (filesystem is a dumb layer ?). Aren't these DIO_xxx_LOCKING flags inside __blockdev_direct_IO() a perfect example why trying to do too many things inside vfs layer for so many filesystems is a bad idea ? By the way, since we're on this subject, could we discuss a little bit about vfs rename call (or I can start another new discussion thread) ?

Note that linux do_rename() starts with the usual lookup logic, followed by "lock_rename", then a final round of dentry lookup, and finally comes to filesystem's i_op->rename call. Since lock_rename() only calls for vfs layer locks that are local to this particular machine, for a cluster filesystem, there exists a huge window between the final lookup and filesystem's i_op->rename calls such that the file could get deleted from another node before fs can do anything about it. Is it possible that we could get a new function pointer (lock_rename) in inode_operations structure so a cluster filesystem can do proper locking ?

It looks like the ocfs2 guys have the similar problem?

http://ftp.kernel.org/pub/linux/kernel/people/mfasheh/ocfs2/ocfs2_git_patches/ocfs2-upstream-linus-20060924/0009-PATCH-Allow-file-systems-to-manually-d_move-inside-of-rename.txt



Thanks for the pointer. Same as ocfs2, under current VFS code, both GFS1/2 also need FS_ODD_RENAME flag for the rename problem - got an ugly ~200 line draft patch ready for GFS1 (and am looking into GFS2 at this moment). The issue here is, for GFS, if vfs lock_rename() can call us, this complication can be greatly reduced. Will start another thread to see whether the wish can be granted.

-- Wendy

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