md-cache: Invalidate cache entry for open() with O_TRUNC

When a file is opened with O_TRUNC flag set, its size gets
set to '0'. This case needs to be handled in md-cache to
avoid sending incorrect cached stat.

This is backport of below mainline patch -
http://review.gluster.org/#/c/15618/

> Change-Id: I95d1f8a6634734898883ede010c3e7b0b7eb97d9
> BUG: 1382266
> Signed-off-by: Soumya Koduri <skoduri@redhat.com>
> Reviewed-on: http://review.gluster.org/15618
> Smoke: Gluster Build System <jenkins@build.gluster.org>
> Reviewed-by: jiffin tony Thottan <jthottan@redhat.com>
> Tested-by: jiffin tony Thottan <jthottan@redhat.com>
> NetBSD-regression: NetBSD Build System <jenkins@build.gluster.org>
> CentOS-regression: Gluster Build System <jenkins@build.gluster.org>
> Reviewed-by: Kaleb KEITHLEY <kkeithle@redhat.com>
> (cherry picked from commit 6ca5d6382f03685b31b12accb095093cf1486603)

Change-Id: I92349f5b48aef07f3790db7aae25bfa2ddb5947e
BUG: 1391450
Signed-off-by: Soumya Koduri <skoduri@redhat.com>
Reviewed-on: http://review.gluster.org/15771
Smoke: Gluster Build System <jenkins@build.gluster.org>
NetBSD-regression: NetBSD Build System <jenkins@build.gluster.org>
CentOS-regression: Gluster Build System <jenkins@build.gluster.org>
Reviewed-by: Kaleb KEITHLEY <kkeithle@redhat.com>

1 files changed, 48 insertions, 0 deletions

diff --git a/xlators/performance/md-cache/src/md-cache.c b/xlators/performance/md-cache/src/md-cache.c
index 31bc8d8187d..30443761c56 100644
--- a/xlators/performance/md-cache/src/md-cache.c
+++ b/xlators/performance/md-cache/src/md-cache.c
@@ -1506,6 +1506,53 @@ mdc_create (call_frame_t *frame, xlator_t *this, loc_t *loc, int flags,
 }
 
 
+static int
+mdc_open_cbk (call_frame_t *frame, void *cookie, xlator_t *this,
+                int32_t op_ret, int32_t op_errno, fd_t *fd,
+                dict_t *xdata)
+{
+        mdc_local_t *local = NULL;
+
+        local = frame->local;
+
+        if (op_ret || !local)
+                goto out;
+
+        if (local->fd->flags & O_TRUNC) {
+                /* O_TRUNC modifies file size. Hence invalidate the
+                 * cache entry to fetch latest attributes. */
+                mdc_inode_iatt_invalidate (this, local->fd->inode);
+        }
+
+out:
+        MDC_STACK_UNWIND (open, frame, op_ret, op_errno, fd, xdata);
+        return 0;
+}
+
+
+static int
+mdc_open (call_frame_t *frame, xlator_t *this, loc_t *loc, int flags,
+          fd_t *fd, dict_t *xdata)
+{
+        mdc_local_t  *local = NULL;
+
+        if (!fd || !IA_ISREG(fd->inode->ia_type) ||
+            !(fd->flags & O_TRUNC)) {
+                goto out;
+        }
+
+        local = mdc_local_get (frame);
+
+        local->fd = fd_ref (fd);
+
+out:
+        STACK_WIND (frame, mdc_open_cbk,
+                    FIRST_CHILD(this), FIRST_CHILD(this)->fops->open,
+                    loc, flags, fd, xdata);
+        return 0;
+}
+
+
 int
 mdc_readv_cbk (call_frame_t *frame, void *cookie, xlator_t *this,
                int32_t op_ret, int32_t op_errno,
@@ -2385,6 +2432,7 @@ struct xlator_fops fops = {
         .rename      = mdc_rename,
         .link        = mdc_link,
         .create      = mdc_create,
+        .open        = mdc_open,
         .readv       = mdc_readv,
         .writev      = mdc_writev,
         .setattr     = mdc_setattr,