On 2018-04-24 17:08, Alberto Garcia wrote: > On Sat 21 Apr 2018 03:29:21 PM CEST, Max Reitz wrote: >> This adds a simple copy-on-read filter driver. It relies on the already >> existing COR functionality in the central block layer code, which may be >> moved here once we no longer need it there. >> >> Signed-off-by: Max Reitz <mre...@redhat.com> > > >> +#define PERM_PASSTHROUGH (BLK_PERM_CONSISTENT_READ \ >> + | BLK_PERM_WRITE \ >> + | BLK_PERM_RESIZE) >> +#define PERM_UNCHANGED (BLK_PERM_ALL & ~PERM_PASSTHROUGH) >> + >> +static void cor_child_perm(BlockDriverState *bs, BdrvChild *c, >> + const BdrvChildRole *role, >> + BlockReopenQueue *reopen_queue, >> + uint64_t perm, uint64_t shared, >> + uint64_t *nperm, uint64_t *nshared) >> +{ >> + if (c == NULL) { >> + *nperm = (perm & PERM_PASSTHROUGH) | BLK_PERM_WRITE_UNCHANGED; >> + *nshared = (shared & PERM_PASSTHROUGH) | PERM_UNCHANGED; >> + return; >> + } >> + >> + *nperm = (perm & PERM_PASSTHROUGH) | >> + (c->perm & PERM_UNCHANGED); > > I admit I'm not completely familiar with this, but don't you need to add > BLK_PERM_WRITE_UNCHANGED to *nperm ?
As long as it's requested in when the child is attached (which it is in the "c == NULL" case), it should be part of c->perm then. (And since PERM_PASSTHROUGH does not contain WRITE_UNCHANGED, it is part of PERM_UNCHANGED.) Max >> + *nshared = (shared & PERM_PASSTHROUGH) | >> + (c->shared_perm & PERM_UNCHANGED); >> +} > > Berto >
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