Re: [PATCH v12 10/12] namei: aggressively check for nd->root escape on ".." resolution
From: Al Viro <viro@zeniv.linux.org.uk>
Date: 2019-09-04 23:30:10
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linux-alpha, linux-arch, linux-arm-kernel, linux-fsdevel, linux-kselftest, linux-mips, linux-s390, linux-sh, linuxppc-dev, lkml, sparclinux
On Wed, Sep 04, 2019 at 03:38:20PM -0700, Linus Torvalds wrote:
On Wed, Sep 4, 2019 at 3:31 PM David Howells [off-list ref] wrote:quoted
It ought to be reasonably easy to make them per-sb at least, I think. We don't allow cross-super rename, right?Right now the sequence count handling very much depends on it being a global entity on the reader side, at least. And while the rename sequence count could (and probably should) be per-sb, the same is very much not true of the mount one.
Huh? That will cost us having to have a per-superblock dentry hash table; recall that lockless lockup can give false negatives if something gets moved from chain to chain, and rename_lock is first and foremost used to catch those and retry. If we split it on per-superblock basis, we can't have dentries from different superblocks in the same chain anymore...