Author: mjg
Date: Mon Sep 7 20:02:56 2015
New Revision: 287539
URL: https://svnweb.freebsd.org/changeset/base/287539
Log:
fd: make the common case in filecaps_copy work lockless
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.
Modified:
head/sys/kern/kern_descrip.c
head/sys/kern/uipc_usrreq.c
head/sys/sys/filedesc.h
Modified: head/sys/kern/kern_descrip.c
==============================================================================
--- head/sys/kern/kern_descrip.c Mon Sep 7 17:56:49 2015
(r287538)
+++ head/sys/kern/kern_descrip.c Mon Sep 7 20:02:56 2015
(r287539)
@@ -911,7 +911,7 @@ kern_dup(struct thread *td, u_int mode,
#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));
-
- 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);
- }
+ if (src->fc_ioctls == NULL)
+ return (0);
+ if (!locked)
+ return (1);
+
+ 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, co
}
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,
*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 file
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
Modified: head/sys/kern/uipc_usrreq.c
==============================================================================
--- head/sys/kern/uipc_usrreq.c Mon Sep 7 17:56:49 2015 (r287538)
+++ head/sys/kern/uipc_usrreq.c Mon Sep 7 20:02:56 2015 (r287539)
@@ -1972,7 +1972,7 @@ unp_internalize(struct mbuf **controlp,
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);
Modified: head/sys/sys/filedesc.h
==============================================================================
--- head/sys/sys/filedesc.h Mon Sep 7 17:56:49 2015 (r287538)
+++ head/sys/sys/filedesc.h Mon Sep 7 20:02:56 2015 (r287539)
@@ -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);
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