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| author | Eric W. Biederman <ebiederm@xmission.com> | 2015-08-15 13:36:41 -0500 |
|---|---|---|
| committer | Al Viro <viro@zeniv.linux.org.uk> | 2015-08-21 02:34:37 -0400 |
| commit | a03e283bf5c3d4851b4998122196ce9f849e6dfb (patch) | |
| tree | 993a15c5162722fa702a490540e8ee374cead082 /fs/dcache.c | |
| parent | cde93be45a8a90d8c264c776fab63487b5038a65 (diff) | |
| download | lwn-a03e283bf5c3d4851b4998122196ce9f849e6dfb.tar.gz lwn-a03e283bf5c3d4851b4998122196ce9f849e6dfb.zip | |
dcache: Reduce the scope of i_lock in d_splice_alias
i_lock is only needed until __d_find_any_alias calls dget on the alias
dentry. After that the reference to new ensures that dentry_kill and
d_delete will not remove the inode from the dentry, and remove the
dentry from the inode->d_entry list.
The inode i_lock came to be held over the the __d_move calls in
d_splice_alias through a series of introduction of locks with
increasing smaller scope. First it was the dcache_lock, then
it was the dcache_inode_lock, and finally inode->i_lock.
Furthermore inode->i_lock is not held over any other calls
to d_move or __d_move so it can not provide any meaningful
rename protection.
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Diffstat (limited to 'fs/dcache.c')
| -rw-r--r-- | fs/dcache.c | 7 |
1 files changed, 3 insertions, 4 deletions
diff --git a/fs/dcache.c b/fs/dcache.c index e3b44ca75a1b..5c33aeb0f68f 100644 --- a/fs/dcache.c +++ b/fs/dcache.c @@ -2718,7 +2718,7 @@ struct dentry *d_ancestor(struct dentry *p1, struct dentry *p2) * This helper attempts to cope with remotely renamed directories * * It assumes that the caller is already holding - * dentry->d_parent->d_inode->i_mutex, inode->i_lock and rename_lock + * dentry->d_parent->d_inode->i_mutex, and rename_lock * * Note: If ever the locking in lock_rename() changes, then please * remember to update this too... @@ -2744,7 +2744,6 @@ out_unalias: __d_move(alias, dentry, false); ret = 0; out_err: - spin_unlock(&inode->i_lock); if (m2) mutex_unlock(m2); if (m1) @@ -2790,10 +2789,11 @@ struct dentry *d_splice_alias(struct inode *inode, struct dentry *dentry) if (S_ISDIR(inode->i_mode)) { struct dentry *new = __d_find_any_alias(inode); if (unlikely(new)) { + /* The reference to new ensures it remains an alias */ + spin_unlock(&inode->i_lock); write_seqlock(&rename_lock); if (unlikely(d_ancestor(new, dentry))) { write_sequnlock(&rename_lock); - spin_unlock(&inode->i_lock); dput(new); new = ERR_PTR(-ELOOP); pr_warn_ratelimited( @@ -2812,7 +2812,6 @@ struct dentry *d_splice_alias(struct inode *inode, struct dentry *dentry) } else { __d_move(new, dentry, false); write_sequnlock(&rename_lock); - spin_unlock(&inode->i_lock); security_d_instantiate(new, inode); } iput(inode); |