From c5bc1b3ff35ae321d018d0c4ba66b062e4fb1e05 Mon Sep 17 00:00:00 2001 From: Jeff Layton Date: Fri, 16 Sep 2022 09:37:51 -0400 Subject: fs: uninline inode_query_iversion Reviewed-by: NeilBrown Reviewed-by: Jan Kara Reviewed-by: Christian Brauner Signed-off-by: Jeff Layton --- fs/libfs.c | 36 ++++++++++++++++++++++++++++++++++++ 1 file changed, 36 insertions(+) (limited to 'fs/libfs.c') diff --git a/fs/libfs.c b/fs/libfs.c index aada4e7c8713..17ecc47696e1 100644 --- a/fs/libfs.c +++ b/fs/libfs.c @@ -1582,3 +1582,39 @@ bool inode_maybe_inc_iversion(struct inode *inode, bool force) return true; } EXPORT_SYMBOL(inode_maybe_inc_iversion); + +/** + * inode_query_iversion - read i_version for later use + * @inode: inode from which i_version should be read + * + * Read the inode i_version counter. This should be used by callers that wish + * to store the returned i_version for later comparison. This will guarantee + * that a later query of the i_version will result in a different value if + * anything has changed. + * + * In this implementation, we fetch the current value, set the QUERIED flag and + * then try to swap it into place with a cmpxchg, if it wasn't already set. If + * that fails, we try again with the newly fetched value from the cmpxchg. + */ +u64 inode_query_iversion(struct inode *inode) +{ + u64 cur, new; + + cur = inode_peek_iversion_raw(inode); + do { + /* If flag is already set, then no need to swap */ + if (cur & I_VERSION_QUERIED) { + /* + * This barrier (and the implicit barrier in the + * cmpxchg below) pairs with the barrier in + * inode_maybe_inc_iversion(). + */ + smp_mb(); + break; + } + + new = cur | I_VERSION_QUERIED; + } while (!atomic64_try_cmpxchg(&inode->i_version, &cur, new)); + return cur >> I_VERSION_QUERIED_SHIFT; +} +EXPORT_SYMBOL(inode_query_iversion); -- cgit v1.2.3