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mem: Add comments

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Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
This commit is contained in:
Pavel Emelyanov
2013-05-16 00:38:26 +04:00
parent 1c9a91a723
commit bfe77ea725
1 changed files with 38 additions and 0 deletions
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38
mem.c
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@@ -211,6 +211,15 @@ static int page_in_parent(unsigned long vaddr, u64 map, struct mem_snap_ctx *sna
return 0; return 0;
} }
/*
* This routine finds out what memory regions to grab from the
* dumpee. The iovs generated are then fed into vmsplice to
* put the memory into the page-pipe's pipe.
*
* "Holes" in page-pipe are regions, that should be dumped, but
* the memory contents is present in the pagent image set.
*/
static int generate_iovs(struct vma_area *vma, int pagemap, struct page_pipe *pp, u64 *map, static int generate_iovs(struct vma_area *vma, int pagemap, struct page_pipe *pp, u64 *map,
struct mem_snap_ctx *snap) struct mem_snap_ctx *snap)
{ {
@@ -310,6 +319,10 @@ static int __parasite_dump_pages_seized(struct parasite_ctl *ctl,
pr_debug(" Private vmas %lu/%lu pages\n", pr_debug(" Private vmas %lu/%lu pages\n",
vma_area_list->longest, vma_area_list->priv_size); vma_area_list->longest, vma_area_list->priv_size);
/*
* Step 0 -- prepare
*/
snap = mem_snap_init(ctl); snap = mem_snap_init(ctl);
if (IS_ERR(snap)) if (IS_ERR(snap))
goto out; goto out;
@@ -333,6 +346,10 @@ static int __parasite_dump_pages_seized(struct parasite_ctl *ctl,
if (!pp) if (!pp)
goto out_close; goto out_close;
/*
* Step 1 -- generate the pagemap
*/
list_for_each_entry(vma_area, &vma_area_list->h, list) { list_for_each_entry(vma_area, &vma_area_list->h, list) {
if (!privately_dump_vma(vma_area)) if (!privately_dump_vma(vma_area))
continue; continue;
@@ -343,6 +360,10 @@ static int __parasite_dump_pages_seized(struct parasite_ctl *ctl,
} }
debug_show_page_pipe(pp); debug_show_page_pipe(pp);
/*
* Step 2 -- grab pages into page-pipe
*/
args->off = 0; args->off = 0;
list_for_each_entry(ppb, &pp->bufs, l) { list_for_each_entry(ppb, &pp->bufs, l) {
@@ -364,6 +385,11 @@ static int __parasite_dump_pages_seized(struct parasite_ctl *ctl,
timing_stop(TIME_MEMDUMP); timing_stop(TIME_MEMDUMP);
/*
* Step 3 -- write pages into image (or delay writing for
* pre-dump action (see pre_dump_one_task)
*/
if (pp_ret) if (pp_ret)
*pp_ret = pp; *pp_ret = pp;
else { else {
@@ -380,6 +406,10 @@ static int __parasite_dump_pages_seized(struct parasite_ctl *ctl,
timing_stop(TIME_MEMWRITE); timing_stop(TIME_MEMWRITE);
} }
/*
* Step 4 -- clean up
*/
task_reset_dirty_track(ctl->pid.real); task_reset_dirty_track(ctl->pid.real);
out_pp: out_pp:
if (ret || !pp_ret) if (ret || !pp_ret)
@@ -403,6 +433,14 @@ int parasite_dump_pages_seized(struct parasite_ctl *ctl,
pargs = prep_dump_pages_args(ctl, vma_area_list); pargs = prep_dump_pages_args(ctl, vma_area_list);
/*
* Add PROT_READ protection for all VMAs we're about to
* dump if they don't have one. Otherwise we'll not be
* able to read the memory contents.
*
* Afterwards -- reprotect memory back.
*/
pargs->add_prot = PROT_READ; pargs->add_prot = PROT_READ;
ret = parasite_execute(PARASITE_CMD_MPROTECT_VMAS, ctl); ret = parasite_execute(PARASITE_CMD_MPROTECT_VMAS, ctl);
if (ret) { if (ret) {