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Message-ID: <20240131004724.GC2020@sol.localdomain> Date: Tue, 30 Jan 2024 16:47:24 -0800 From: Eric Biggers <ebiggers@...nel.org> To: Gabriel Krisman Bertazi <krisman@...e.de> Cc: viro@...iv.linux.org.uk, jaegeuk@...nel.org, tytso@....edu, amir73il@...il.com, linux-ext4@...r.kernel.org, linux-f2fs-devel@...ts.sourceforge.net, linux-fsdevel@...r.kernel.org Subject: Re: [PATCH v5 04/12] fscrypt: Drop d_revalidate for valid dentries during lookup On Mon, Jan 29, 2024 at 05:43:22PM -0300, Gabriel Krisman Bertazi wrote: > Unencrypted and encrypted-dentries where the key is available don't need > to be revalidated with regards to fscrypt, since they don't go stale > from under VFS and the key cannot be removed for the encrypted case > without evicting the dentry. Mark them with d_set_always_valid, to "d_set_always_valid" doesn't appear in the diff itself. > diff --git a/include/linux/fscrypt.h b/include/linux/fscrypt.h > index 4aaf847955c0..a22997b9f35c 100644 > --- a/include/linux/fscrypt.h > +++ b/include/linux/fscrypt.h > @@ -942,11 +942,22 @@ static inline int fscrypt_prepare_rename(struct inode *old_dir, > static inline void fscrypt_prepare_lookup_dentry(struct dentry *dentry, > bool is_nokey_name) > { > - if (is_nokey_name) { > - spin_lock(&dentry->d_lock); > + spin_lock(&dentry->d_lock); > + > + if (is_nokey_name) > dentry->d_flags |= DCACHE_NOKEY_NAME; > - spin_unlock(&dentry->d_lock); > + else if (dentry->d_flags & DCACHE_OP_REVALIDATE && > + dentry->d_op->d_revalidate == fscrypt_d_revalidate) { > + /* > + * Unencrypted dentries and encrypted dentries where the > + * key is available are always valid from fscrypt > + * perspective. Avoid the cost of calling > + * fscrypt_d_revalidate unnecessarily. > + */ > + dentry->d_flags &= ~DCACHE_OP_REVALIDATE; > } > + > + spin_unlock(&dentry->d_lock); This makes lookups in unencrypted directories start doing the spin_lock/spin_unlock pair. Is that really necessary? These changes also make the inline function fscrypt_prepare_lookup() very long (when including the fscrypt_prepare_lookup_dentry() that's inlined into it). The rule that I'm trying to follow is that to the extent that the fscrypt helper functions are inlined, the inline part should be a fast path for unencrypted directories. Encrypted directories should be handled out-of-line. So looking at the original fscrypt_prepare_lookup(): static inline int fscrypt_prepare_lookup(struct inode *dir, struct dentry *dentry, struct fscrypt_name *fname) { if (IS_ENCRYPTED(dir)) return __fscrypt_prepare_lookup(dir, dentry, fname); memset(fname, 0, sizeof(*fname)); fname->usr_fname = &dentry->d_name; fname->disk_name.name = (unsigned char *)dentry->d_name.name; fname->disk_name.len = dentry->d_name.len; return 0; } If you could just add the DCACHE_OP_REVALIDATE clearing for dentries in unencrypted directories just before the "return 0;", hopefully without the spinlock, that would be good. Yes, that does mean that __fscrypt_prepare_lookup() will have to handle it too, for the case of dentries in encrypted directories, but that seems okay. - Eric
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