| Message ID | 20170216121140.9061-3-pasic@linux.vnet.ibm.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
* Halil Pasic (pasic@linux.vnet.ibm.com) wrote: > Currently vmstate_base_addr does several things: it pinpoints the field > within the struct, possibly allocates memory and possibly does the first > pointer dereference. Obviously allocation is needed only for load. > > Let us split up the functionality in vmstate_base_addr and move the > address manipulations (that is everything but the allocation logic) to > load and save so it becomes more obvious what is actually going on. Like > this all the address calculations (and the handling of the flags > controlling these) is in one place and the sequence is more obvious. > > The newly introduced function vmstate_handle_alloc also fixes the > allocation for the unused VMS_VBUFFER| VMS_MULTIPLY scenario and is > substantially simpler than the original vmstate_base_addr. Note that VMSTATE_VBUFFER_MULTIPLY does use VMS_VBUFFER|VMS_MULTIPLY - but not with alloc (and I started using VMSTATE_VBUFFER_MULTIPLY in a recent patch that went in). I'm not sure I see what the error is that you fixed. However, I'm ok with it: Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com> > In load and save some asserts are added so it's easier to debug > situations where we would end up with a null pointer dereference. > > Signed-off-by: Halil Pasic <pasic@linux.vnet.ibm.com> > --- > migration/vmstate.c | 39 +++++++++++++++++---------------------- > 1 file changed, 17 insertions(+), 22 deletions(-) > > diff --git a/migration/vmstate.c b/migration/vmstate.c > index 36efa80..836a7a4 100644 > --- a/migration/vmstate.c > +++ b/migration/vmstate.c > @@ -52,29 +52,15 @@ static int vmstate_size(void *opaque, VMStateField *field) > return size; > } > > -static void *vmstate_base_addr(void *opaque, VMStateField *field, bool alloc) > +static void vmstate_handle_alloc(void *ptr, VMStateField *field, void *opaque) > { > - void *base_addr = opaque + field->offset; > - > - if (field->flags & VMS_POINTER) { > - if (alloc && (field->flags & VMS_ALLOC)) { > - gsize size = 0; > - if (field->flags & VMS_VBUFFER) { > - size = vmstate_size(opaque, field); > - } else { > - int n_elems = vmstate_n_elems(opaque, field); > - if (n_elems) { > - size = n_elems * field->size; > - } > - } > - if (size) { > - *(void **)base_addr = g_malloc(size); > - } > + if (field->flags & VMS_POINTER && field->flags & VMS_ALLOC) { > + gsize size = vmstate_size(opaque, field); > + size *= vmstate_n_elems(opaque, field); > + if (size) { > + *(void **)ptr = g_malloc(size); > } > - base_addr = *(void **)base_addr; > } > - > - return base_addr; > } > > int vmstate_load_state(QEMUFile *f, const VMStateDescription *vmsd, > @@ -116,10 +102,15 @@ int vmstate_load_state(QEMUFile *f, const VMStateDescription *vmsd, > field->field_exists(opaque, version_id)) || > (!field->field_exists && > field->version_id <= version_id)) { > - void *first_elem = vmstate_base_addr(opaque, field, true); > + void *first_elem = opaque + field->offset; > int i, n_elems = vmstate_n_elems(opaque, field); > int size = vmstate_size(opaque, field); > > + vmstate_handle_alloc(first_elem, field, opaque); > + if (field->flags & VMS_POINTER) { > + first_elem = *(void **)first_elem; > + assert(first_elem || !n_elems); > + } > for (i = 0; i < n_elems; i++) { > void *curr_elem = first_elem + size * i; > > @@ -321,13 +312,17 @@ void vmstate_save_state(QEMUFile *f, const VMStateDescription *vmsd, > while (field->name) { > if (!field->field_exists || > field->field_exists(opaque, vmsd->version_id)) { > - void *first_elem = vmstate_base_addr(opaque, field, false); > + void *first_elem = opaque + field->offset; > int i, n_elems = vmstate_n_elems(opaque, field); > int size = vmstate_size(opaque, field); > int64_t old_offset, written_bytes; > QJSON *vmdesc_loop = vmdesc; > > trace_vmstate_save_state_loop(vmsd->name, field->name, n_elems); > + if (field->flags & VMS_POINTER) { > + first_elem = *(void **)first_elem; > + assert(first_elem || !n_elems); > + } > for (i = 0; i < n_elems; i++) { > void *curr_elem = first_elem + size * i; > > -- > 2.8.4 > -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK
On 02/21/2017 01:07 PM, Dr. David Alan Gilbert wrote: > * Halil Pasic (pasic@linux.vnet.ibm.com) wrote: >> Currently vmstate_base_addr does several things: it pinpoints the field >> within the struct, possibly allocates memory and possibly does the first >> pointer dereference. Obviously allocation is needed only for load. >> >> Let us split up the functionality in vmstate_base_addr and move the >> address manipulations (that is everything but the allocation logic) to >> load and save so it becomes more obvious what is actually going on. Like >> this all the address calculations (and the handling of the flags >> controlling these) is in one place and the sequence is more obvious. >> >> The newly introduced function vmstate_handle_alloc also fixes the >> allocation for the unused VMS_VBUFFER| VMS_MULTIPLY scenario and is s/VMS_VBUFFER| VMS_MULTIPLY/VMS_VBUFFER|VMS_MULTIPLY|VMS_ALLOC/ >> substantially simpler than the original vmstate_base_addr. > > Note that VMSTATE_VBUFFER_MULTIPLY does use VMS_VBUFFER|VMS_MULTIPLY - but > not with alloc (and I started using VMSTATE_VBUFFER_MULTIPLY in a recent > patch that went in). Adding |VMS_ALLOC to avoid confusion. I was hoping it's clear form the context that we are talking about scenarios where allocation is relevant. > I'm not sure I see what the error is that you fixed. I'm referring to number of bytes allocated. It was vmstate_n_elems(opaque, field) * field->size and became vmstate_n_elems(opaque, field) * vmstate_size(opaque, field) vmstate_size does extra handling for VMS_VBUFFER and VMS_MULTIPLY. > > However, I'm ok with it: > > Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com> > Cheers, Halil >> In load and save some asserts are added so it's easier to debug >> situations where we would end up with a null pointer dereference. >> >> Signed-off-by: Halil Pasic <pasic@linux.vnet.ibm.com> >> --- >> migration/vmstate.c | 39 +++++++++++++++++---------------------- >> 1 file changed, 17 insertions(+), 22 deletions(-) >> >> diff --git a/migration/vmstate.c b/migration/vmstate.c >> index 36efa80..836a7a4 100644 >> --- a/migration/vmstate.c >> +++ b/migration/vmstate.c >> @@ -52,29 +52,15 @@ static int vmstate_size(void *opaque, VMStateField *field) >> return size; >> } >> >> -static void *vmstate_base_addr(void *opaque, VMStateField *field, bool alloc) >> +static void vmstate_handle_alloc(void *ptr, VMStateField *field, void *opaque) > >> { >> - void *base_addr = opaque + field->offset; >> - >> - if (field->flags & VMS_POINTER) { >> - if (alloc && (field->flags & VMS_ALLOC)) { >> - gsize size = 0; >> - if (field->flags & VMS_VBUFFER) { >> - size = vmstate_size(opaque, field); >> - } else { >> - int n_elems = vmstate_n_elems(opaque, field); >> - if (n_elems) { >> - size = n_elems * field->size; >> - } >> - } >> - if (size) { >> - *(void **)base_addr = g_malloc(size); >> - } >> + if (field->flags & VMS_POINTER && field->flags & VMS_ALLOC) { >> + gsize size = vmstate_size(opaque, field); >> + size *= vmstate_n_elems(opaque, field); >> + if (size) { >> + *(void **)ptr = g_malloc(size); >> } >> - base_addr = *(void **)base_addr; >> } >> - >> - return base_addr; >> } >> >> int vmstate_load_state(QEMUFile *f, const VMStateDescription *vmsd, >> @@ -116,10 +102,15 @@ int vmstate_load_state(QEMUFile *f, const VMStateDescription *vmsd, >> field->field_exists(opaque, version_id)) || >> (!field->field_exists && >> field->version_id <= version_id)) { >> - void *first_elem = vmstate_base_addr(opaque, field, true); >> + void *first_elem = opaque + field->offset; >> int i, n_elems = vmstate_n_elems(opaque, field); >> int size = vmstate_size(opaque, field); >> >> + vmstate_handle_alloc(first_elem, field, opaque); >> + if (field->flags & VMS_POINTER) { >> + first_elem = *(void **)first_elem; >> + assert(first_elem || !n_elems); >> + } >> for (i = 0; i < n_elems; i++) { >> void *curr_elem = first_elem + size * i; >> >> @@ -321,13 +312,17 @@ void vmstate_save_state(QEMUFile *f, const VMStateDescription *vmsd, >> while (field->name) { >> if (!field->field_exists || >> field->field_exists(opaque, vmsd->version_id)) { >> - void *first_elem = vmstate_base_addr(opaque, field, false); >> + void *first_elem = opaque + field->offset; >> int i, n_elems = vmstate_n_elems(opaque, field); >> int size = vmstate_size(opaque, field); >> int64_t old_offset, written_bytes; >> QJSON *vmdesc_loop = vmdesc; >> >> trace_vmstate_save_state_loop(vmsd->name, field->name, n_elems); >> + if (field->flags & VMS_POINTER) { >> + first_elem = *(void **)first_elem; >> + assert(first_elem || !n_elems); >> + } >> for (i = 0; i < n_elems; i++) { >> void *curr_elem = first_elem + size * i; >> >> -- >> 2.8.4 >> > -- > Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK >
diff --git a/migration/vmstate.c b/migration/vmstate.c index 36efa80..836a7a4 100644 --- a/migration/vmstate.c +++ b/migration/vmstate.c @@ -52,29 +52,15 @@ static int vmstate_size(void *opaque, VMStateField *field) return size; } -static void *vmstate_base_addr(void *opaque, VMStateField *field, bool alloc) +static void vmstate_handle_alloc(void *ptr, VMStateField *field, void *opaque) { - void *base_addr = opaque + field->offset; - - if (field->flags & VMS_POINTER) { - if (alloc && (field->flags & VMS_ALLOC)) { - gsize size = 0; - if (field->flags & VMS_VBUFFER) { - size = vmstate_size(opaque, field); - } else { - int n_elems = vmstate_n_elems(opaque, field); - if (n_elems) { - size = n_elems * field->size; - } - } - if (size) { - *(void **)base_addr = g_malloc(size); - } + if (field->flags & VMS_POINTER && field->flags & VMS_ALLOC) { + gsize size = vmstate_size(opaque, field); + size *= vmstate_n_elems(opaque, field); + if (size) { + *(void **)ptr = g_malloc(size); } - base_addr = *(void **)base_addr; } - - return base_addr; } int vmstate_load_state(QEMUFile *f, const VMStateDescription *vmsd, @@ -116,10 +102,15 @@ int vmstate_load_state(QEMUFile *f, const VMStateDescription *vmsd, field->field_exists(opaque, version_id)) || (!field->field_exists && field->version_id <= version_id)) { - void *first_elem = vmstate_base_addr(opaque, field, true); + void *first_elem = opaque + field->offset; int i, n_elems = vmstate_n_elems(opaque, field); int size = vmstate_size(opaque, field); + vmstate_handle_alloc(first_elem, field, opaque); + if (field->flags & VMS_POINTER) { + first_elem = *(void **)first_elem; + assert(first_elem || !n_elems); + } for (i = 0; i < n_elems; i++) { void *curr_elem = first_elem + size * i; @@ -321,13 +312,17 @@ void vmstate_save_state(QEMUFile *f, const VMStateDescription *vmsd, while (field->name) { if (!field->field_exists || field->field_exists(opaque, vmsd->version_id)) { - void *first_elem = vmstate_base_addr(opaque, field, false); + void *first_elem = opaque + field->offset; int i, n_elems = vmstate_n_elems(opaque, field); int size = vmstate_size(opaque, field); int64_t old_offset, written_bytes; QJSON *vmdesc_loop = vmdesc; trace_vmstate_save_state_loop(vmsd->name, field->name, n_elems); + if (field->flags & VMS_POINTER) { + first_elem = *(void **)first_elem; + assert(first_elem || !n_elems); + } for (i = 0; i < n_elems; i++) { void *curr_elem = first_elem + size * i;
Currently vmstate_base_addr does several things: it pinpoints the field within the struct, possibly allocates memory and possibly does the first pointer dereference. Obviously allocation is needed only for load. Let us split up the functionality in vmstate_base_addr and move the address manipulations (that is everything but the allocation logic) to load and save so it becomes more obvious what is actually going on. Like this all the address calculations (and the handling of the flags controlling these) is in one place and the sequence is more obvious. The newly introduced function vmstate_handle_alloc also fixes the allocation for the unused VMS_VBUFFER| VMS_MULTIPLY scenario and is substantially simpler than the original vmstate_base_addr. In load and save some asserts are added so it's easier to debug situations where we would end up with a null pointer dereference. Signed-off-by: Halil Pasic <pasic@linux.vnet.ibm.com> --- migration/vmstate.c | 39 +++++++++++++++++---------------------- 1 file changed, 17 insertions(+), 22 deletions(-)