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 <paulmck@xxxxxxxxxxxxxxxxxx>
Acked-by: Will Deacon <will.deacon@xxxxxxx>
Acked-by: Mark Rutland <mark.rutland@xxxxxxx>
---
Documentation/filesystems/path-lookup.md | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
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
------------------
--
2.5.2
