| Message ID | 20190402154600.32432-8-ebiggers@kernel.org |
|---|---|
| State | Not Applicable |
| Headers | show |
| Series | fscrypt: key management improvements | expand |
On Tue, Apr 02, 2019 at 08:45:50AM -0700, Eric Biggers wrote: > From: Eric Biggers <ebiggers@google.com> > > When a filesystem encryption key is removed, we need all files which had > been "unlocked" (had ->i_crypt_info set up) with it to appear "locked" > again. This is most easily done by evicting the inodes. This can > currently be done using 'echo 2 > /proc/sys/vm/drop_caches'; however, > that is overkill and not usable by non-root users. > > To evict just the needed inodes we also need the ability to evict those > inodes' dentries, since an inode is pinned by its dentries. Therefore, > add a function shrink_dcache_inode() which iterates through an inode's > dentries and evicts any unused ones as well as any unused descendants > (since there may be negative dentries pinning the inode's dentries). Huh? > + * Evict all unused aliases of the specified inode from the dcache. This is > + * intended to be used when trying to evict a specific inode, since inodes are > + * pinned by their dentries. We also have to descend to ->d_subdirs for each > + * alias, since aliases may be pinned by negative child dentries. > + */ > +void shrink_dcache_inode(struct inode *inode) > +{ > + for (;;) { > + struct select_data data; > + struct dentry *dentry; > + > + INIT_LIST_HEAD(&data.dispose); > + data.start = NULL; > + data.found = 0; > + > + spin_lock(&inode->i_lock); > + hlist_for_each_entry(dentry, &inode->i_dentry, d_u.d_alias) > + d_walk(dentry, &data, select_collect); > + spin_unlock(&inode->i_lock); > + > + if (!data.found) > + break; > + > + shrink_dentry_list(&data.dispose); > + cond_resched(); This is... odd. What's wrong with if (S_ISDIR(inode->i_mode)) { dentry = d_find_any_alias(inode); if (dentry) { shrink_dcache_parent(dentry); dput(dentry); } } d_prune_aliases(inode); instead of that thing?
On Wed, Apr 03, 2019 at 07:34:12PM +0100, Al Viro wrote: > On Tue, Apr 02, 2019 at 08:45:50AM -0700, Eric Biggers wrote: > > From: Eric Biggers <ebiggers@google.com> > > > > When a filesystem encryption key is removed, we need all files which had > > been "unlocked" (had ->i_crypt_info set up) with it to appear "locked" > > again. This is most easily done by evicting the inodes. This can > > currently be done using 'echo 2 > /proc/sys/vm/drop_caches'; however, > > that is overkill and not usable by non-root users. > > > > To evict just the needed inodes we also need the ability to evict those > > inodes' dentries, since an inode is pinned by its dentries. Therefore, > > add a function shrink_dcache_inode() which iterates through an inode's > > dentries and evicts any unused ones as well as any unused descendants > > (since there may be negative dentries pinning the inode's dentries). > > Huh? > > > + * Evict all unused aliases of the specified inode from the dcache. This is > > + * intended to be used when trying to evict a specific inode, since inodes are > > + * pinned by their dentries. We also have to descend to ->d_subdirs for each > > + * alias, since aliases may be pinned by negative child dentries. > > + */ > > +void shrink_dcache_inode(struct inode *inode) > > +{ > > + for (;;) { > > + struct select_data data; > > + struct dentry *dentry; > > + > > + INIT_LIST_HEAD(&data.dispose); > > + data.start = NULL; > > + data.found = 0; > > + > > + spin_lock(&inode->i_lock); > > + hlist_for_each_entry(dentry, &inode->i_dentry, d_u.d_alias) > > + d_walk(dentry, &data, select_collect); > > + spin_unlock(&inode->i_lock); > > + > > + if (!data.found) > > + break; > > + > > + shrink_dentry_list(&data.dispose); > > + cond_resched(); > > This is... odd. What's wrong with > if (S_ISDIR(inode->i_mode)) { > dentry = d_find_any_alias(inode); > if (dentry) { > shrink_dcache_parent(dentry); > dput(dentry); > } > } > d_prune_aliases(inode); > instead of that thing? That works, as far as I can tell, so I'll do that instead. I don't think I noticed that d_prune_aliases() existed when I wrote this. Thanks for the suggestion! - Eric
diff --git a/fs/dcache.c b/fs/dcache.c index aac41adf47433..1d940484c2d17 100644 --- a/fs/dcache.c +++ b/fs/dcache.c @@ -1507,6 +1507,38 @@ void shrink_dcache_parent(struct dentry *parent) } EXPORT_SYMBOL(shrink_dcache_parent); +/** + * shrink_dcache_inode - prune dcache for inode + * @inode: inode to prune + * + * Evict all unused aliases of the specified inode from the dcache. This is + * intended to be used when trying to evict a specific inode, since inodes are + * pinned by their dentries. We also have to descend to ->d_subdirs for each + * alias, since aliases may be pinned by negative child dentries. + */ +void shrink_dcache_inode(struct inode *inode) +{ + for (;;) { + struct select_data data; + struct dentry *dentry; + + INIT_LIST_HEAD(&data.dispose); + data.start = NULL; + data.found = 0; + + spin_lock(&inode->i_lock); + hlist_for_each_entry(dentry, &inode->i_dentry, d_u.d_alias) + d_walk(dentry, &data, select_collect); + spin_unlock(&inode->i_lock); + + if (!data.found) + break; + + shrink_dentry_list(&data.dispose); + cond_resched(); + } +} + static enum d_walk_ret umount_check(void *_data, struct dentry *dentry) { /* it has busy descendents; complain about those instead */ diff --git a/include/linux/dcache.h b/include/linux/dcache.h index 60996e64c5798..1b5f295dc1156 100644 --- a/include/linux/dcache.h +++ b/include/linux/dcache.h @@ -246,6 +246,7 @@ extern struct dentry * d_obtain_alias(struct inode *); extern struct dentry * d_obtain_root(struct inode *); extern void shrink_dcache_sb(struct super_block *); extern void shrink_dcache_parent(struct dentry *); +extern void shrink_dcache_inode(struct inode *); extern void shrink_dcache_for_umount(struct super_block *); extern void d_invalidate(struct dentry *);