From 36b0bd86321436a951f225fcf2e921390ed8dc33 Mon Sep 17 00:00:00 2001

From: Michael Adam <obnox@samba.org>

Date: Thu, 20 Jun 2019 13:09:37 +0200

Subject: [PATCH 223/255] change get_real_filename implementation to use

 ENOATTR instead of ENOENT

get_real_filename is implemented as a virtual extended attribute to help

Samba implement the case-insensitive but case preserving SMB protocol

more efficiently. It is implemented as a getxattr call on the parent directory

with the virtual key of "get_real_filename:<entryname>" by looking for a

spelling with different case for the provided file/dir name (<entryname>)

and returning this correct spelling as a result if the entry is found.

Originally (05aaec645a6262d431486eb5ac7cd702646cfcfb), the

implementation used the ENOENT errno to return the authoritative answer

that <entryname> does not exist in any case folding.

Now this implementation is actually a violation or misuse of the defined

API for the getxattr call which returns ENOENT for the case that the dir

that the call is made against does not exist and ENOATTR (or the synonym

ENODATA) for the case that the xattr does not exist.

This was not a problem until the gluster fuse-bridge was changed

to do map ENOENT to ESTALE in 59629f1da9dca670d5dcc6425f7f89b3e96b46bf,

after which we the getxattr call for get_real_filename returned an

ESTALE instead of ENOENT breaking the expectation in Samba.

It is an independent problem that ESTALE should not leak out to user

space but is intended to trigger retries between fuse and gluster.

But nevertheless, the semantics seem to be incorrect here and should

be changed.

This patch changes the implementation of the get_real_filename virtual

xattr to correctly return ENOATTR instead of ENOENT if the file/directory

being looked up is not found.

The Samba glusterfs_fuse vfs module which takes advantage of the

get_real_filename over a fuse mount will receive a corresponding change

to map ENOATTR to ENOENT. Without this change, it will still work

correctly, but the performance optimization for nonexisting files is

lost. On the other hand side, this change removes the distinction

between the old not-implemented case and the implemented case.

So Samba changed to treat ENOATTR like ENOENT will not work correctly

any more against old servers that don't implement get_real_filename.

I.e. existing files will be reported as non-existing

Backport of https://review.gluster.org/c/glusterfs/+/22925

Change-Id: I971b427ab8410636d5d201157d9af70e0d075b67

fixes: bz#1724089

Signed-off-by: Michael Adam <obnox@samba.org>

Reviewed-on: https://code.engineering.redhat.com/gerrit/175012

Tested-by: RHGS Build Bot <nigelb@redhat.com>

Reviewed-by: Atin Mukherjee <amukherj@redhat.com>

---

 xlators/cluster/dht/src/dht-common.c           | 8 ++++----

 xlators/storage/posix/src/posix-inode-fd-ops.c | 4 ++--

 2 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/xlators/cluster/dht/src/dht-common.c b/xlators/cluster/dht/src/dht-common.c

index 9a6ea5b..219b072 100644

--- a/xlators/cluster/dht/src/dht-common.c

+++ b/xlators/cluster/dht/src/dht-common.c

@@ -4618,7 +4618,7 @@ dht_getxattr_get_real_filename_cbk(call_frame_t *frame, void *cookie,

     LOCK(&frame->lock);

     {

-        if (local->op_errno == ENODATA || local->op_errno == EOPNOTSUPP) {

+        if (local->op_errno == EOPNOTSUPP) {

             /* Nothing to do here, we have already found

              * a subvol which does not have the get_real_filename

              * optimization. If condition is for simple logic.

@@ -4627,7 +4627,7 @@ dht_getxattr_get_real_filename_cbk(call_frame_t *frame, void *cookie,

         }

         if (op_ret == -1) {

-            if (op_errno == ENODATA || op_errno == EOPNOTSUPP) {

+            if (op_errno == EOPNOTSUPP) {

                 /* This subvol does not have the optimization.

                  * Better let the user know we don't support it.

                  * Remove previous results if any.

@@ -4655,7 +4655,7 @@ dht_getxattr_get_real_filename_cbk(call_frame_t *frame, void *cookie,

                 goto post_unlock;

             }

-            if (op_errno == ENOENT) {

+            if (op_errno == ENOATTR) {

                 /* Do nothing, our defaults are set to this.

                  */

                 goto unlock;

@@ -4723,7 +4723,7 @@ dht_getxattr_get_real_filename(call_frame_t *frame, xlator_t *this, loc_t *loc,

     cnt = local->call_cnt = layout->cnt;

     local->op_ret = -1;

-    local->op_errno = ENOENT;

+    local->op_errno = ENOATTR;

     for (i = 0; i < cnt; i++) {

         subvol = layout->list[i].xlator;

diff --git a/xlators/storage/posix/src/posix-inode-fd-ops.c b/xlators/storage/posix/src/posix-inode-fd-ops.c

index c949f68..ea3b69c 100644

--- a/xlators/storage/posix/src/posix-inode-fd-ops.c

+++ b/xlators/storage/posix/src/posix-inode-fd-ops.c

@@ -2954,7 +2954,7 @@ posix_xattr_get_real_filename(call_frame_t *frame, xlator_t *this, loc_t *loc,

     (void)sys_closedir(fd);

     if (!found)

-        return -ENOENT;

+        return -ENOATTR;

     ret = dict_set_dynstr(dict, (char *)key, found);

     if (ret) {

@@ -3422,7 +3422,7 @@ posix_getxattr(call_frame_t *frame, xlator_t *this, loc_t *loc,

         if (ret < 0) {

             op_ret = -1;

             op_errno = -ret;

-            if (op_errno == ENOENT) {

+            if (op_errno == ENOATTR) {

                 gf_msg_debug(this->name, 0,

                              "Failed to get "

                              "real filename (%s, %s)",

-- 

1.8.3.1