The branch, master has been updated
via 3b2d8bd vfs_glusterfs: Add comments to the pipe(2) code.
from fba69f4 selftest: Run krb5.kdc test against users with a UPN
https://git.samba.org/?p=samba.git;a=shortlog;h=master
- Log -----------------------------------------------------------------
commit 3b2d8bdbb1851961536241d3aaaf6ac936964517
Author: Ira Cooper <[email protected]>
Date: Thu Jan 22 17:14:31 2015 -0500
vfs_glusterfs: Add comments to the pipe(2) code.
The guarantees around read(2) and write(2) and pipes are critical
to understanding this code. Hopefully these comments will help.
Signed-off-by: Ira Cooper <[email protected]>
Reviewed-by: Jeremy Allison <[email protected]>
Autobuild-User(master): Jeremy Allison <[email protected]>
Autobuild-Date(master): Fri Jan 23 20:58:51 CET 2015 on sn-devel-104
-----------------------------------------------------------------------
Summary of changes:
source3/modules/vfs_glusterfs.c | 17 +++++++++++++++++
1 file changed, 17 insertions(+)
Changeset truncated at 500 lines:
diff --git a/source3/modules/vfs_glusterfs.c b/source3/modules/vfs_glusterfs.c
index 04314f2..e0cc85c 100644
--- a/source3/modules/vfs_glusterfs.c
+++ b/source3/modules/vfs_glusterfs.c
@@ -521,6 +521,13 @@ static void aio_glusterfs_done(glfs_fd_t *fd, ssize_t ret,
void *data)
* be called here, as it is not designed to be executed
* in the multithread environment, tevent_req_done() must be
* executed from the smbd main thread.
+ *
+ * write(2) on pipes with sizes under _POSIX_PIPE_BUF
+ * in size is atomic, without this, the use op pipes in this
+ * code would not work.
+ *
+ * sys_write is a thin enough wrapper around write(2)
+ * that we can trust it here.
*/
sts = sys_write(write_fd, &req, sizeof(struct tevent_req *));
@@ -541,6 +548,16 @@ static void aio_tevent_fd_done(struct tevent_context
*event_ctx,
struct tevent_req *req = NULL;
int sts = 0;
+ /*
+ * read(2) on pipes is atomic if the needed data is available
+ * in the pipe, per SUS and POSIX. Because we always write
+ * to the pipe in sizeof(struct tevent_req *) chunks, we can
+ * always read in those chunks, atomically.
+ *
+ * sys_read is a thin enough wrapper around read(2) that we
+ * can trust it here.
+ */
+
sts = sys_read(read_fd, &req, sizeof(struct tevent_req *));
if (sts < 0) {
DEBUG(0,("\nRead from pipe failed (%s)", strerror(errno)));
--
Samba Shared Repository
