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posixshm: switch to OBJT_SWAP in advance of other changes

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Future changes to posixshm will start tracking writeable mappings in order
to support file sealing. Tracking writeable mappings for an OBJT_DEFAULT
object is complicated as it may be swapped out and converted to an
OBJT_SWAP. One may generically add this tracking for vm_object, but this is
difficult to do without increasing memory footprint of vm_object and blowing
up memory usage by a significant amount.

On the other hand, the swap pager can be expanded to track writeable
mappings without increasing vm_object size. This change is currently in
D21456. Switch over to OBJT_SWAP in advance of the other changes to the
swap pager and posixshm.
This commit is contained in:
kevans 2019-09-01 00:33:16 +00:00
parent 8a4d833254
commit c72c92d361
1 changed files with 1 additions and 1 deletions
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2
sys/kern/uipc_shm.c
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@ -549,7 +549,7 @@ shm_alloc(struct ucred *ucred, mode_t mode)
shmfd->shm_uid = ucred->cr_uid;
shmfd->shm_gid = ucred->cr_gid;
shmfd->shm_mode = mode;
shmfd->shm_object = vm_pager_allocate(OBJT_DEFAULT, NULL,
shmfd->shm_object = vm_pager_allocate(OBJT_SWAP, NULL,
shmfd->shm_size, VM_PROT_DEFAULT, 0, ucred);
KASSERT(shmfd->shm_object != NULL, ("shm_create: vm_pager_allocate"));
shmfd->shm_object->pg_color = 0;