| Message ID | 20170321031635.22123-5-famz@redhat.com |
|---|---|
| State | New |
| Headers | show |
On Tue, Mar 21, 2017 at 11:16:23AM +0800, Fam Zheng wrote: > @@ -1713,21 +1714,22 @@ void bdrv_format_default_perms(BlockDriverState *bs, BdrvChild *c, > perm |= BLK_PERM_CONSISTENT_READ; > shared &= ~(BLK_PERM_WRITE | BLK_PERM_RESIZE); > } else { > - /* We want consistent read from backing files if the parent needs it. > + /* We want consistent read and aio context change from backing files if > + * the parent needs it. > * No other operations are performed on backing files. */ > - perm &= BLK_PERM_CONSISTENT_READ; > + perm &= BLK_PERM_CONSISTENT_READ | BLK_PERM_AIO_CONTEXT_CHANGE; > > - /* If the parent can deal with changing data, we're okay with a > + /* If the parent can deal with changing aio context, we're okay too; > + * If the parent can deal with changing data, we're okay with a > * writable and resizable backing file. */ > /* TODO Require !(perm & BLK_PERM_CONSISTENT_READ), too? */ > + shared &= BLK_PERM_AIO_CONTEXT_CHANGE | BLK_PERM_WRITE; > if (shared & BLK_PERM_WRITE) { > - shared = BLK_PERM_WRITE | BLK_PERM_RESIZE; > - } else { > - shared = 0; > + shared |= BLK_PERM_WRITE | BLK_PERM_RESIZE; We already have BLK_PERM_WRITE so we're just adding BLK_PERM_RESIZE. The following is clearer: shared |= BLK_PERM_RESIZE; > } > > shared |= BLK_PERM_CONSISTENT_READ | BLK_PERM_GRAPH_MOD | > - BLK_PERM_WRITE_UNCHANGED; > + BLK_PERM_WRITE_UNCHANGED | BLK_PERM_AIO_CONTEXT_CHANGE; Why was shared &= BLK_PERM_AIO_CONTEXT_CHANGE necessary above if we unconditionally OR it here?
On Mon, 04/10 09:57, Stefan Hajnoczi wrote: > On Tue, Mar 21, 2017 at 11:16:23AM +0800, Fam Zheng wrote: > > @@ -1713,21 +1714,22 @@ void bdrv_format_default_perms(BlockDriverState *bs, BdrvChild *c, > > perm |= BLK_PERM_CONSISTENT_READ; > > shared &= ~(BLK_PERM_WRITE | BLK_PERM_RESIZE); > > } else { > > - /* We want consistent read from backing files if the parent needs it. > > + /* We want consistent read and aio context change from backing files if > > + * the parent needs it. > > * No other operations are performed on backing files. */ > > - perm &= BLK_PERM_CONSISTENT_READ; > > + perm &= BLK_PERM_CONSISTENT_READ | BLK_PERM_AIO_CONTEXT_CHANGE; > > > > - /* If the parent can deal with changing data, we're okay with a > > + /* If the parent can deal with changing aio context, we're okay too; > > + * If the parent can deal with changing data, we're okay with a > > * writable and resizable backing file. */ > > /* TODO Require !(perm & BLK_PERM_CONSISTENT_READ), too? */ > > + shared &= BLK_PERM_AIO_CONTEXT_CHANGE | BLK_PERM_WRITE; > > if (shared & BLK_PERM_WRITE) { > > - shared = BLK_PERM_WRITE | BLK_PERM_RESIZE; > > - } else { > > - shared = 0; > > + shared |= BLK_PERM_WRITE | BLK_PERM_RESIZE; > > We already have BLK_PERM_WRITE so we're just adding BLK_PERM_RESIZE. > The following is clearer: > > shared |= BLK_PERM_RESIZE; > > > } > > > > shared |= BLK_PERM_CONSISTENT_READ | BLK_PERM_GRAPH_MOD | > > - BLK_PERM_WRITE_UNCHANGED; > > + BLK_PERM_WRITE_UNCHANGED | BLK_PERM_AIO_CONTEXT_CHANGE; > > Why was shared &= BLK_PERM_AIO_CONTEXT_CHANGE necessary above if we > unconditionally OR it here? It's redundant. Will fix both. Fam
diff --git a/block.c b/block.c index ae9327b..0190087 100644 --- a/block.c +++ b/block.c @@ -1670,7 +1670,8 @@ int bdrv_child_try_set_perm(BdrvChild *c, uint64_t perm, uint64_t shared, #define DEFAULT_PERM_PASSTHROUGH (BLK_PERM_CONSISTENT_READ \ | BLK_PERM_WRITE \ | BLK_PERM_WRITE_UNCHANGED \ - | BLK_PERM_RESIZE) + | BLK_PERM_RESIZE \ + | BLK_PERM_AIO_CONTEXT_CHANGE) #define DEFAULT_PERM_UNCHANGED (BLK_PERM_ALL & ~DEFAULT_PERM_PASSTHROUGH) void bdrv_filter_default_perms(BlockDriverState *bs, BdrvChild *c, @@ -1713,21 +1714,22 @@ void bdrv_format_default_perms(BlockDriverState *bs, BdrvChild *c, perm |= BLK_PERM_CONSISTENT_READ; shared &= ~(BLK_PERM_WRITE | BLK_PERM_RESIZE); } else { - /* We want consistent read from backing files if the parent needs it. + /* We want consistent read and aio context change from backing files if + * the parent needs it. * No other operations are performed on backing files. */ - perm &= BLK_PERM_CONSISTENT_READ; + perm &= BLK_PERM_CONSISTENT_READ | BLK_PERM_AIO_CONTEXT_CHANGE; - /* If the parent can deal with changing data, we're okay with a + /* If the parent can deal with changing aio context, we're okay too; + * If the parent can deal with changing data, we're okay with a * writable and resizable backing file. */ /* TODO Require !(perm & BLK_PERM_CONSISTENT_READ), too? */ + shared &= BLK_PERM_AIO_CONTEXT_CHANGE | BLK_PERM_WRITE; if (shared & BLK_PERM_WRITE) { - shared = BLK_PERM_WRITE | BLK_PERM_RESIZE; - } else { - shared = 0; + shared |= BLK_PERM_WRITE | BLK_PERM_RESIZE; } shared |= BLK_PERM_CONSISTENT_READ | BLK_PERM_GRAPH_MOD | - BLK_PERM_WRITE_UNCHANGED; + BLK_PERM_WRITE_UNCHANGED | BLK_PERM_AIO_CONTEXT_CHANGE; } *nperm = perm; diff --git a/block/vvfat.c b/block/vvfat.c index af5153d..70ce452 100644 --- a/block/vvfat.c +++ b/block/vvfat.c @@ -3080,7 +3080,7 @@ static void vvfat_child_perm(BlockDriverState *bs, BdrvChild *c, if (c == s->qcow) { /* This is a private node, nobody should try to attach to it */ *nperm = BLK_PERM_CONSISTENT_READ | BLK_PERM_WRITE; - *nshared = BLK_PERM_WRITE_UNCHANGED; + *nshared = BLK_PERM_WRITE_UNCHANGED | BLK_PERM_AIO_CONTEXT_CHANGE; } else { /* The backing file is there so 'commit' can use it. vvfat doesn't * access it in any way. */
bdrv_set_aio_context can take care of children recursively, so it is okay to pass down the perm. Signed-off-by: Fam Zheng <famz@redhat.com> --- block.c | 18 ++++++++++-------- block/vvfat.c | 2 +- 2 files changed, 11 insertions(+), 9 deletions(-)