From ee549d8b1c8cd482bb84d49e7535e174fd89b9ea Mon Sep 17 00:00:00 2001

From: Kevin Wolf <kwolf@redhat.com>

Date: Fri, 15 Mar 2019 18:10:10 +0100

Subject: [PATCH 014/163] file-posix: Make auto-read-only dynamic

RH-Author: Kevin Wolf <kwolf@redhat.com>

Message-id: <20190315181010.14964-15-kwolf@redhat.com>

Patchwork-id: 84891

O-Subject: [RHEL-7.7 qemu-kvm-rhev PATCH 14/14] file-posix: Make auto-read-only dynamic

Bugzilla: 1685989

RH-Acked-by: John Snow <jsnow@redhat.com>

RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com>

RH-Acked-by: Miroslav Rezanina <mrezanin@redhat.com>

Until now, with auto-read-only=on we tried to open the file read-write

first and if that failed, read-only was tried. This is actually not good

enough for libvirt, which gives QEMU SELinux permissions for read-write

only as soon as it actually intends to write to the image. So we need to

be able to switch between read-only and read-write at runtime.

This patch makes auto-read-only dynamic, i.e. the file is opened

read-only as long as no user of the node has requested write

permissions, but it is automatically reopened read-write as soon as the

first writer is attached. Conversely, if the last writer goes away, the

file is reopened read-only again.

bs->read_only is no longer set for auto-read-only=on files even if the

file descriptor is opened read-only because it will be transparently

upgraded as soon as a writer is attached. This changes the output of

qemu-iotests 232.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>

(cherry picked from commit 23dece19da41724349809873923e20a48b619cb7)

Signed-off-by: Kevin Wolf <kwolf@redhat.com>

Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>

---

 block/file-posix.c         | 36 +++++++++++++++++-------------------

 tests/qemu-iotests/232.out | 12 ++++++------

 2 files changed, 23 insertions(+), 25 deletions(-)

diff --git a/block/file-posix.c b/block/file-posix.c

index f0f8eaf..0cf7261 100644

--- a/block/file-posix.c

+++ b/block/file-posix.c

@@ -382,13 +382,21 @@ static void raw_probe_alignment(BlockDriverState *bs, int fd, Error **errp)

     }

 }

-static void raw_parse_flags(int bdrv_flags, int *open_flags)

+static void raw_parse_flags(int bdrv_flags, int *open_flags, bool has_writers)

 {

+    bool read_write = false;

     assert(open_flags != NULL);

     *open_flags |= O_BINARY;

     *open_flags &= ~O_ACCMODE;

-    if (bdrv_flags & BDRV_O_RDWR) {

+

+    if (bdrv_flags & BDRV_O_AUTO_RDONLY) {

+        read_write = has_writers;

+    } else if (bdrv_flags & BDRV_O_RDWR) {

+        read_write = true;

+    }

+

+    if (read_write) {

         *open_flags |= O_RDWR;

     } else {

         *open_flags |= O_RDONLY;

@@ -516,24 +524,12 @@ static int raw_open_common(BlockDriverState *bs, QDict *options,

     }

     s->open_flags = open_flags;

-    raw_parse_flags(bdrv_flags, &s->open_flags);

+    raw_parse_flags(bdrv_flags, &s->open_flags, false);

     s->fd = -1;

     fd = qemu_open(filename, s->open_flags, 0644);

     ret = fd < 0 ? -errno : 0;

-    if (ret == -EACCES || ret == -EROFS) {

-        /* Try to degrade to read-only, but if it doesn't work, still use the

-         * normal error message. */

-        if (bdrv_apply_auto_read_only(bs, NULL, NULL) == 0) {

-            bdrv_flags &= ~BDRV_O_RDWR;

-            raw_parse_flags(bdrv_flags, &s->open_flags);

-            assert(!(s->open_flags & O_CREAT));

-            fd = qemu_open(filename, s->open_flags);

-            ret = fd < 0 ? -errno : 0;

-        }

-    }

-

     if (ret < 0) {

         error_setg_errno(errp, -ret, "Could not open '%s'", filename);

         if (ret == -EROFS) {

@@ -838,12 +834,14 @@ static int raw_handle_perm_lock(BlockDriverState *bs,

 }

 static int raw_reconfigure_getfd(BlockDriverState *bs, int flags,

-                                 int *open_flags, bool force_dup,

+                                 int *open_flags, uint64_t perm, bool force_dup,

                                  Error **errp)

 {

     BDRVRawState *s = bs->opaque;

     int fd = -1;

     int ret;

+    bool has_writers = perm &

+        (BLK_PERM_WRITE | BLK_PERM_WRITE_UNCHANGED | BLK_PERM_RESIZE);

     int fcntl_flags = O_APPEND | O_NONBLOCK;

 #ifdef O_NOATIME

     fcntl_flags |= O_NOATIME;

@@ -854,7 +852,7 @@ static int raw_reconfigure_getfd(BlockDriverState *bs, int flags,

         *open_flags |= O_NONBLOCK;

     }

-    raw_parse_flags(flags, open_flags);

+    raw_parse_flags(flags, open_flags, has_writers);

 #ifdef O_ASYNC

     /* Not all operating systems have O_ASYNC, and those that don't

@@ -916,7 +914,7 @@ static int raw_reopen_prepare(BDRVReopenState *state,

     rs = state->opaque;

     rs->fd = raw_reconfigure_getfd(state->bs, state->flags, &rs->open_flags,

-                                   true, &local_err);

+                                   state->perm, true, &local_err);

     if (local_err) {

         error_propagate(errp, local_err);

         ret = -1;

@@ -2548,7 +2546,7 @@ static int raw_check_perm(BlockDriverState *bs, uint64_t perm, uint64_t shared,

         s->perm_change_fd = rs->fd;

     } else {

         /* We may need a new fd if auto-read-only switches the mode */

-        ret = raw_reconfigure_getfd(bs, bs->open_flags, &open_flags,

+        ret = raw_reconfigure_getfd(bs, bs->open_flags, &open_flags, perm,

                                     false, errp);

         if (ret < 0) {

             return ret;

diff --git a/tests/qemu-iotests/232.out b/tests/qemu-iotests/232.out

index dcb683a..3bd1a92 100644

--- a/tests/qemu-iotests/232.out

+++ b/tests/qemu-iotests/232.out

@@ -22,12 +22,12 @@ NODE_NAME: TEST_DIR/t.IMGFMT (file, read-only)

 NODE_NAME: TEST_DIR/t.IMGFMT (file, read-only)

 QEMU_PROG: -drive driver=file,file=TEST_DIR/t.IMGFMT,if=none,read-only=off,auto-read-only=off: Could not open 'TEST_DIR/t.IMGFMT': Permission denied

-NODE_NAME: TEST_DIR/t.IMGFMT (file, read-only)

-NODE_NAME: TEST_DIR/t.IMGFMT (file, read-only)

+NODE_NAME: TEST_DIR/t.IMGFMT (file)

+NODE_NAME: TEST_DIR/t.IMGFMT (file)

 QEMU_PROG: -drive driver=file,file=TEST_DIR/t.IMGFMT,if=none,auto-read-only=off: Could not open 'TEST_DIR/t.IMGFMT': Permission denied

-NODE_NAME: TEST_DIR/t.IMGFMT (file, read-only)

-NODE_NAME: TEST_DIR/t.IMGFMT (file, read-only)

+NODE_NAME: TEST_DIR/t.IMGFMT (file)

+NODE_NAME: TEST_DIR/t.IMGFMT (file)

 === -blockdev with read-write image: read-only/auto-read-only combinations ===

@@ -50,10 +50,10 @@ node0: TEST_DIR/t.IMGFMT (file, read-only)

 node0: TEST_DIR/t.IMGFMT (file, read-only)

 QEMU_PROG: -blockdev driver=file,filename=TEST_DIR/t.IMGFMT,node-name=node0,read-only=off,auto-read-only=off: Could not open 'TEST_DIR/t.IMGFMT': Permission denied

-node0: TEST_DIR/t.IMGFMT (file, read-only)

+node0: TEST_DIR/t.IMGFMT (file)

 QEMU_PROG: -blockdev driver=file,filename=TEST_DIR/t.IMGFMT,node-name=node0,read-only=off: Could not open 'TEST_DIR/t.IMGFMT': Permission denied

 QEMU_PROG: -blockdev driver=file,filename=TEST_DIR/t.IMGFMT,node-name=node0,auto-read-only=off: Could not open 'TEST_DIR/t.IMGFMT': Permission denied

-node0: TEST_DIR/t.IMGFMT (file, read-only)

+node0: TEST_DIR/t.IMGFMT (file)

 QEMU_PROG: -blockdev driver=file,filename=TEST_DIR/t.IMGFMT,node-name=node0: Could not open 'TEST_DIR/t.IMGFMT': Permission denied

 *** done

-- 

1.8.3.1