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authorEric Biggers <ebiggers@google.com>2019-04-10 13:21:14 -0700
committerTheodore Ts'o <tytso@mit.edu>2019-04-17 12:43:14 -0400
commit4c4f7c19b3c721aed418bc97907b411608c5c6a0 (patch)
treef277f0ab8ee56d45ad6ae93950645c405ac7f49c /fs/namei.c
parentb01531db6cec2aa330dbc91bfbfaaef4a0d387a4 (diff)
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vfs: use READ_ONCE() to access ->i_link
Use 'READ_ONCE(inode->i_link)' to explicitly support filesystems caching the symlink target in ->i_link later if it was unavailable at iget() time, or wasn't easily available. I'll be doing this in fscrypt, to improve the performance of encrypted symlinks on ext4, f2fs, and ubifs. ->i_link will start NULL and may later be set to a non-NULL value by a smp_store_release() or cmpxchg_release(). READ_ONCE() is needed on the read side. smp_load_acquire() is unnecessary because only a data dependency barrier is required. (Thanks to Al for pointing this out.) Acked-by: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: Eric Biggers <ebiggers@google.com> Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Diffstat (limited to 'fs/namei.c')
-rw-r--r--fs/namei.c4
1 files changed, 2 insertions, 2 deletions
diff --git a/fs/namei.c b/fs/namei.c
index dede0147b3f6..2855de004c1a 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -1066,7 +1066,7 @@ const char *get_link(struct nameidata *nd)
return ERR_PTR(error);
nd->last_type = LAST_BIND;
- res = inode->i_link;
+ res = READ_ONCE(inode->i_link);
if (!res) {
const char * (*get)(struct dentry *, struct inode *,
struct delayed_call *);
@@ -4729,7 +4729,7 @@ int vfs_readlink(struct dentry *dentry, char __user *buffer, int buflen)
spin_unlock(&inode->i_lock);
}
- link = inode->i_link;
+ link = READ_ONCE(inode->i_link);
if (!link) {
link = inode->i_op->get_link(dentry, inode, &done);
if (IS_ERR(link))