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fd: make the common case in filecaps_copy work lockless

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The filedesc lock is only needed if ioctls caps are present, which is a
rare situation. This is a step towards reducing the scope of the filedesc
lock.
This commit is contained in:
Mateusz Guzik 2015-09-07 20:02:56 +00:00
parent 40ea8e710e
commit d7832811a7
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=287539
3 changed files with 27 additions and 16 deletions
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38
sys/kern/kern_descrip.c
View File

@ -911,7 +911,7 @@ kern_dup(struct thread *td, u_int mode, int flags, int old, int new)
#endif
filecaps_free(&newfde->fde_caps);
memcpy(newfde, oldfde, fde_change_size);
filecaps_copy(&oldfde->fde_caps, &newfde->fde_caps);
filecaps_copy(&oldfde->fde_caps, &newfde->fde_caps, true);
if ((flags & FDDUP_FLAG_CLOEXEC) != 0)
newfde->fde_flags = oldfde->fde_flags | UF_EXCLOSE;
else
@ -1433,21 +1433,31 @@ filecaps_init(struct filecaps *fcaps)
/*
* Copy filecaps structure allocating memory for ioctls array if needed.
*
* The last parameter indicates whether the fdtable is locked. If it is not and
* ioctls are encountered, copying fails and the caller must lock the table.
*
* Note that if the table was not locked, the caller has to check the relevant
* sequence counter to determine whether the operation was successful.
*/
void
filecaps_copy(const struct filecaps *src, struct filecaps *dst)
int
filecaps_copy(const struct filecaps *src, struct filecaps *dst, bool locked)
{
size_t size;
*dst = *src;
if (src->fc_ioctls != NULL) {
KASSERT(src->fc_nioctls > 0,
("fc_ioctls != NULL, but fc_nioctls=%hd", src->fc_nioctls));
if (src->fc_ioctls == NULL)
return (0);
if (!locked)
return (1);
size = sizeof(src->fc_ioctls[0]) * src->fc_nioctls;
dst->fc_ioctls = malloc(size, M_FILECAPS, M_WAITOK);
bcopy(src->fc_ioctls, dst->fc_ioctls, size);
}
KASSERT(src->fc_nioctls > 0,
("fc_ioctls != NULL, but fc_nioctls=%hd", src->fc_nioctls));
size = sizeof(src->fc_ioctls[0]) * src->fc_nioctls;
dst->fc_ioctls = malloc(size, M_FILECAPS, M_WAITOK);
bcopy(src->fc_ioctls, dst->fc_ioctls, size);
return (0);
}
/*
@ -1956,7 +1966,7 @@ fdcopy(struct filedesc *fdp)
}
nfde = &newfdp->fd_ofiles[i];
*nfde = *ofde;
filecaps_copy(&ofde->fde_caps, &nfde->fde_caps);
filecaps_copy(&ofde->fde_caps, &nfde->fde_caps, true);
fhold(nfde->fde_file);
fdused_init(newfdp, i);
newfdp->fd_lastfile = i;
@ -2012,7 +2022,7 @@ fdcopy_remapped(struct filedesc *fdp, const int *fds, size_t nfds,
}
nfde = &newfdp->fd_ofiles[i];
*nfde = *ofde;
filecaps_copy(&ofde->fde_caps, &nfde->fde_caps);
filecaps_copy(&ofde->fde_caps, &nfde->fde_caps, true);
fhold(nfde->fde_file);
fdused_init(newfdp, i);
newfdp->fd_lastfile = i;
@ -2723,7 +2733,7 @@ fgetvp_rights(struct thread *td, int fd, cap_rights_t *needrightsp,
*vpp = fp->f_vnode;
vref(*vpp);
filecaps_copy(&fdp->fd_ofiles[fd].fde_caps, havecaps);
filecaps_copy(&fdp->fd_ofiles[fd].fde_caps, havecaps, true);
return (0);
}
@ -2938,7 +2948,7 @@ dupfdopen(struct thread *td, struct filedesc *fdp, int dfd, int mode,
seq_write_begin(&newfde->fde_seq);
#endif
memcpy(newfde, oldfde, fde_change_size);
filecaps_copy(&oldfde->fde_caps, &newfde->fde_caps);
filecaps_copy(&oldfde->fde_caps, &newfde->fde_caps, true);
#ifdef CAPABILITIES
seq_write_end(&newfde->fde_seq);
#endif

2
sys/kern/uipc_usrreq.c
View File

@ -1972,7 +1972,7 @@ unp_internalize(struct mbuf **controlp, struct thread *td)
fdep[i] = fdev;
fdep[i]->fde_file = fde->fde_file;
filecaps_copy(&fde->fde_caps,
&fdep[i]->fde_caps);
&fdep[i]->fde_caps, true);
unp_internalize_fp(fdep[i]->fde_file);
}
FILEDESC_SUNLOCK(fdesc);

3
sys/sys/filedesc.h
View File

@ -153,7 +153,8 @@ enum {
struct thread;
void filecaps_init(struct filecaps *fcaps);
void filecaps_copy(const struct filecaps *src, struct filecaps *dst);
int filecaps_copy(const struct filecaps *src, struct filecaps *dst,
bool locked);
void filecaps_move(struct filecaps *src, struct filecaps *dst);
void filecaps_free(struct filecaps *fcaps);