From 3587679d93d0b0e4c31e5a2ad1dffdfcb77e8526 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Mon, 23 Oct 2017 14:07:24 -0700 Subject: locking/atomics, doc/filesystems: Convert ACCESS_ONCE() references For several reasons, it is desirable to use {READ,WRITE}_ONCE() in preference to ACCESS_ONCE(), and new code is expected to use one of the former. So far, there's been no reason to change most existing uses of ACCESS_ONCE(), as these aren't currently harmful. However, for some features it is necessary to instrument reads and writes separately, which is not possible with ACCESS_ONCE(). This distinction is critical to correct operation. It's possible to transform the bulk of kernel code using the Coccinelle script below. However, this doesn't handle documentation, leaving references to ACCESS_ONCE() instances which have been removed. As a preparatory step, this patch converts the filesystems documentation to use {READ,WRITE}_ONCE() consistently. ---- virtual patch @ depends on patch @ expression E1, E2; @@ - ACCESS_ONCE(E1) = E2 + WRITE_ONCE(E1, E2) @ depends on patch @ expression E; @@ - ACCESS_ONCE(E) + READ_ONCE(E) ---- Signed-off-by: Paul E. McKenney Acked-by: Will Deacon Acked-by: Mark Rutland Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: davem@davemloft.net Cc: linux-arch@vger.kernel.org Cc: mpe@ellerman.id.au Cc: shuah@kernel.org Cc: snitzer@redhat.com Cc: thor.thayer@linux.intel.com Cc: tj@kernel.org Cc: viro@zeniv.linux.org.uk Link: http://lkml.kernel.org/r/1508792849-3115-14-git-send-email-paulmck@linux.vnet.ibm.com Signed-off-by: Ingo Molnar --- Documentation/filesystems/path-lookup.md | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) (limited to 'Documentation/filesystems') diff --git a/Documentation/filesystems/path-lookup.md b/Documentation/filesystems/path-lookup.md index 1b39e084a2b2..1933ef734e63 100644 --- a/Documentation/filesystems/path-lookup.md +++ b/Documentation/filesystems/path-lookup.md @@ -826,9 +826,9 @@ If the filesystem may need to revalidate dcache entries, then *is* passed the dentry but does not have access to the `inode` or the `seq` number from the `nameidata`, so it needs to be extra careful when accessing fields in the dentry. This "extra care" typically -involves using `ACCESS_ONCE()` or the newer [`READ_ONCE()`] to access -fields, and verifying the result is not NULL before using it. This -pattern can be see in `nfs_lookup_revalidate()`. +involves using [`READ_ONCE()`] to access fields, and verifying the +result is not NULL before using it. This pattern can be seen in +`nfs_lookup_revalidate()`. A pair of patterns ------------------ -- cgit