[PATCH] pci: Repair pci_save/restore_state so we can restore one save many times.

Because we do not reserve space for the pci-x and pci-e state in struct
pci dev we need to dynamically allocate it. However because we need
to support restore being called multiple times after a single save
it is never safe to free the buffers we have allocated to hold the
state.

So this patch modifies the save routines to first check to see
if we have already allocated a state buffer before allocating
a new one. Then the restore routines are modified to not free
the state after restoring it. Simple and it fixes some subtle
error path handling bugs, that are hard to test for.

Signed-off-by: Eric W. Biederman <[e-mail]>
Signed-off-by: Greg Kroah-Hartman <[e-mail]>
Acked-by: Auke Kok <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

drivers/pci/pci.c

···
 	if (pos <= 0)
 		return 0;
 
-	save_state = kzalloc(sizeof(*save_state) + sizeof(u16) * 4, GFP_KERNEL);
+	save_state = pci_find_saved_cap(dev, PCI_CAP_ID_EXP);
+	if (!save_state)
+		save_state = kzalloc(sizeof(*save_state) + sizeof(u16) * 4, GFP_KERNEL);
 	if (!save_state) {
 		dev_err(&dev->dev, "Out of memory in pci_save_pcie_state\n");
 		return -ENOMEM;
···
 	pci_write_config_word(dev, pos + PCI_EXP_LNKCTL, cap[i++]);
 	pci_write_config_word(dev, pos + PCI_EXP_SLTCTL, cap[i++]);
 	pci_write_config_word(dev, pos + PCI_EXP_RTCTL, cap[i++]);
-	pci_remove_saved_cap(save_state);
-	kfree(save_state);
 }
 
 
···
 	if (pos <= 0)
 		return 0;
 
-	save_state = kzalloc(sizeof(*save_state) + sizeof(u16), GFP_KERNEL);
+	save_state = pci_find_saved_cap(dev, PCI_CAP_ID_EXP);
+	if (!save_state)
+		save_state = kzalloc(sizeof(*save_state) + sizeof(u16), GFP_KERNEL);
 	if (!save_state) {
 		dev_err(&dev->dev, "Out of memory in pci_save_pcie_state\n");
 		return -ENOMEM;
···
 	cap = (u16 *)&save_state->data[0];
 
 	pci_write_config_word(dev, pos + PCI_X_CMD, cap[i++]);
-	pci_remove_saved_cap(save_state);
-	kfree(save_state);
 }
 
 

include/linux/pci.h

···
 	hlist_add_head(&new_cap->next, &pci_dev->saved_cap_space);
 }
 
-static inline void pci_remove_saved_cap(struct pci_cap_saved_state *cap)
-{
-	hlist_del(&cap->next);
-}
-
 /*
  *  For PCI devices, the region numbers are assigned this way:
  *