On 3/2/20 10:03 PM, Chandan Rajendra wrote:
On Sunday, February 23, 2020 7:36 AM Allison Collins wrote:
This patch modifies the attr remove routines to be delay ready. This means they no
longer roll or commit transactions, but instead return -EAGAIN to have the calling
routine roll and refresh the transaction. In this series, xfs_attr_remove_args has
become xfs_attr_remove_iter, which uses a sort of state machine like switch to keep
track of where it was when EAGAIN was returned. xfs_attr_node_removename has also
been modified to use the switch, and a new version of xfs_attr_remove_args
consists of a simple loop to refresh the transaction until the operation is
completed.
This patch also adds a new struct xfs_delattr_context, which we will use to keep
track of the current state of an attribute operation. The new xfs_delattr_state
enum is used to track various operations that are in progress so that we know not
to repeat them, and resume where we left off before EAGAIN was returned to cycle
out the transaction. Other members take the place of local variables that need
to retain their values across multiple function recalls.
Below is a state machine diagram for attr remove operations. The XFS_DAS_* states
indicate places where the function would return -EAGAIN, and then immediately
resume from after being recalled by the calling function. States marked as a
"subroutine state" indicate that they belong to a subroutine, and so the calling
function needs to pass them back to that subroutine to allow it to finish where
it left off. But they otherwise do not have a role in the calling function other
than just passing through.
xfs_attr_remove_iter()
XFS_DAS_RM_SHRINK ─â”
(subroutine state) │
│
XFS_DAS_RMTVAL_REMOVE ─┤
(subroutine state) │
└─>xfs_attr_node_removename()
│
v
need to remove
┌─n── rmt blocks?
│ │
│ y
│ │
│ v
│ ┌─>XFS_DAS_RMTVAL_REMOVE
│ │ │
│ │ v
│ └──y── more blks
│ to remove?
│ │
│ n
│ │
│ v
│ need to
└─────> shrink tree? ─n─â”
│ │
y │
│ │
v │
XFS_DAS_RM_SHRINK │
│ │
v │
done <─────┘
Signed-off-by: Allison Collins <allison.henderson@xxxxxxxxxx>
---
fs/xfs/libxfs/xfs_attr.c | 114 +++++++++++++++++++++++++++++++++++++------
fs/xfs/libxfs/xfs_attr.h | 1 +
fs/xfs/libxfs/xfs_da_btree.h | 30 ++++++++++++
fs/xfs/scrub/common.c | 2 +
fs/xfs/xfs_acl.c | 2 +
fs/xfs/xfs_attr_list.c | 1 +
fs/xfs/xfs_ioctl.c | 2 +
fs/xfs/xfs_ioctl32.c | 2 +
fs/xfs/xfs_iops.c | 2 +
fs/xfs/xfs_xattr.c | 1 +
10 files changed, 141 insertions(+), 16 deletions(-)
diff --git a/fs/xfs/libxfs/xfs_attr.c b/fs/xfs/libxfs/xfs_attr.c
index 5d73bdf..cd3a3f7 100644
--- a/fs/xfs/libxfs/xfs_attr.c
+++ b/fs/xfs/libxfs/xfs_attr.c
@@ -368,11 +368,60 @@ xfs_has_attr(
*/
int
xfs_attr_remove_args(
+ struct xfs_da_args *args)
+{
+ int error = 0;
+ int err2 = 0;
+
+ do {
+ error = xfs_attr_remove_iter(args);
+ if (error && error != -EAGAIN)
+ goto out;
+
+ if (args->dac.flags & XFS_DAC_FINISH_TRANS) {
+ args->dac.flags &= ~XFS_DAC_FINISH_TRANS;
+
+ err2 = xfs_defer_finish(&args->trans);
+ if (err2) {
+ error = err2;
+ goto out;
+ }
+ }
+
+ err2 = xfs_trans_roll_inode(&args->trans, args->dp);
+ if (err2) {
+ error = err2;
+ goto out;
+ }
+
+ } while (error == -EAGAIN);
+out:
+ return error;
+}
+
+/*
+ * Remove the attribute specified in @args.
+ *
+ * This function may return -EAGAIN to signal that the transaction needs to be
+ * rolled. Callers should continue calling this function until they receive a
+ * return value other than -EAGAIN.
+ */
+int
+xfs_attr_remove_iter(
struct xfs_da_args *args)
{
struct xfs_inode *dp = args->dp;
int error;
+ /* State machine switch */
+ switch (args->dac.dela_state) {
+ case XFS_DAS_RM_SHRINK:
+ case XFS_DAS_RMTVAL_REMOVE:
+ goto node;
+ default:
+ break;
+ }
+
On the very first invocation of xfs_attr_remote_iter() from
xfs_attr_remove_args() (via a call from xfs_attr_remove()),
args->dac.dela_state is set to a value of 0. This happens because
xfs_attr_args_init() invokes memset() on args. A value of 0 for
args->dac.dela_state maps to XFS_DAS_RM_SHRINK.
If the xattr was stored in say local or leaf format we end up incorrectly
invoking xfs_attr_node_removename() right?
Hi Chandan,
Yes, this came up in one of the other reviews too. The indexing for the
XFS_DAS_* enum should start at 1, not zero. I had pulled it out of the
last version thinking it would be ok, but I should have kept the
indexing starting at 1, allowing the switch to fall through to default.
Allison
