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mm/khugepaged: refactor collapse_file control flow

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Add a rollback label to deal with failure, instead of continuously
checking for RESULT_SUCCESS, to make it easier to add more failure cases. 
The refactoring also allows the collapse_file tracepoint to include hpage
on success (instead of NULL).

Link: https://lkml.kernel.org/r/20230404120117.2562166-3-stevensd@google.com
Signed-off-by: David Stevens <stevensd@chromium.org>
Acked-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Yang Shi <shy828301@gmail.com>
Acked-by: Hugh Dickins <hughd@google.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Jiaqi Yan <jiaqiyan@google.com>
Cc: "Kirill A. Shutemov" <kirill@shutemov.name>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
David Stevens 2023-04-04 21:01:15 +09:00 • committed by Andrew Morton
parent efa3d814fa
commit cae106dd67
1 changed files with 119 additions and 123 deletions
Download patch file Download diff file Expand all files Collapse all files

40
mm/khugepaged.c
View file

@ -1894,6 +1894,12 @@ static int collapse_file(struct mm_struct *mm, unsigned long addr,
if (result != SCAN_SUCCEED)
goto out;
__SetPageLocked(hpage);
if (is_shmem)
__SetPageSwapBacked(hpage);
hpage->index = start;
hpage->mapping = mapping;
/*
* Ensure we have slots for all the pages in the range. This is
* almost certainly a no-op because most of the pages must be present
@ -1906,16 +1912,10 @@ static int collapse_file(struct mm_struct *mm, unsigned long addr,
xas_unlock_irq(&xas);
if (!xas_nomem(&xas, GFP_KERNEL)) {
result = SCAN_FAIL;
goto out;
goto rollback;
}
} while (1);
__SetPageLocked(hpage);
if (is_shmem)
__SetPageSwapBacked(hpage);
hpage->index = start;
hpage->mapping = mapping;
/*
* At this point the hpage is locked and not up-to-date.
* It's safe to insert it into the page cache, because nobody would
@ -2152,7 +2152,9 @@ xa_unlocked:
*/
try_to_unmap_flush();
if (result == SCAN_SUCCEED) {
if (result != SCAN_SUCCEED)
goto rollback;
/*
* Replacing old pages with new one has succeeded, now we
* attempt to copy the contents.
@ -2163,21 +2165,17 @@ xa_unlocked:
clear_highpage(hpage + (index % HPAGE_PMD_NR));
index++;
}
if (copy_mc_highpage(hpage + (page->index % HPAGE_PMD_NR),
page) > 0) {
if (copy_mc_highpage(hpage + (page->index % HPAGE_PMD_NR), page) > 0) {
result = SCAN_COPY_MC;
break;
goto rollback;
}
index++;
}
while (result == SCAN_SUCCEED && index < end) {
while (index < end) {
clear_highpage(hpage + (index % HPAGE_PMD_NR));
index++;
}
}
nr = thp_nr_pages(hpage);
if (result == SCAN_SUCCEED) {
/*
* Copying old pages to huge one has succeeded, now we
* need to free the old pages.
@ -2192,6 +2190,7 @@ xa_unlocked:
put_page(page);
}
nr = thp_nr_pages(hpage);
xas_lock_irq(&xas);
if (is_shmem)
__mod_lruvec_page_state(hpage, NR_SHMEM_THPS, nr);
@ -2222,8 +2221,9 @@ xa_unlocked:
result = retract_page_tables(mapping, start, mm, addr, hpage,
cc);
unlock_page(hpage);
hpage = NULL;
} else {
goto out;
rollback:
/* Something went wrong: roll back page cache changes */
xas_lock_irq(&xas);
if (nr_none) {
@ -2274,15 +2274,11 @@ xa_unlocked:
xas_unlock_irq(&xas);
hpage->mapping = NULL;
}
if (hpage)
unlock_page(hpage);
put_page(hpage);
out:
VM_BUG_ON(!list_empty(&pagelist));
if (hpage)
put_page(hpage);
trace_mm_khugepaged_collapse_file(mm, hpage, index, is_shmem, addr, file, nr, result);
return result;
}