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XArray: add xas_split

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In order to use multi-index entries for huge pages in the page cache, we
need to be able to split a multi-index entry (eg if a file is truncated in
the middle of a huge page entry).  This version does not support splitting
more than one level of the tree at a time.  This is an acceptable
limitation for the page cache as we do not expect to support order-12
pages in the near future.

[akpm@linux-foundation.org: export xas_split_alloc() to modules]
[willy@infradead.org: fix xarray split]
  Link: https://lkml.kernel.org/r/20200910175450.GV6583@casper.infradead.org
[willy@infradead.org: fix xarray]
  Link: https://lkml.kernel.org/r/20201001233943.GW20115@casper.infradead.org

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: "Kirill A . Shutemov" <kirill@shutemov.name>
Cc: Qian Cai <cai@lca.pw>
Cc: Song Liu <songliubraving@fb.com>
Link: https://lkml.kernel.org/r/20200903183029.14930-3-willy@infradead.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Matthew Wilcox (Oracle)
2020-10-15 20:05:16 -07:00
committed by Linus Torvalds
parent 57417cebc9
commit 8fc75643c5
4 changed files with 224 additions and 15 deletions
Download Patch File Download Diff File Expand all files Collapse all files

44
lib/test_xarray.c
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@@ -1503,6 +1503,49 @@ static noinline void check_store_range(struct xarray *xa)
}
}
#ifdef CONFIG_XARRAY_MULTI
static void check_split_1(struct xarray *xa, unsigned long index,
unsigned int order)
{
XA_STATE(xas, xa, index);
void *entry;
unsigned int i = 0;
xa_store_order(xa, index, order, xa, GFP_KERNEL);
xas_split_alloc(&xas, xa, order, GFP_KERNEL);
xas_lock(&xas);
xas_split(&xas, xa, order);
xas_unlock(&xas);
xa_for_each(xa, index, entry) {
XA_BUG_ON(xa, entry != xa);
i++;
}
XA_BUG_ON(xa, i != 1 << order);
xa_set_mark(xa, index, XA_MARK_0);
XA_BUG_ON(xa, !xa_get_mark(xa, index, XA_MARK_0));
xa_destroy(xa);
}
static noinline void check_split(struct xarray *xa)
{
unsigned int order;
XA_BUG_ON(xa, !xa_empty(xa));
for (order = 1; order < 2 * XA_CHUNK_SHIFT; order++) {
check_split_1(xa, 0, order);
check_split_1(xa, 1UL << order, order);
check_split_1(xa, 3UL << order, order);
}
}
#else
static void check_split(struct xarray *xa) { }
#endif
static void check_align_1(struct xarray *xa, char *name)
{
int i;
@@ -1729,6 +1772,7 @@ static int xarray_checks(void)
check_store_range(&array);
check_store_iter(&array);
check_align(&xa0);
check_split(&array);
check_workingset(&array, 0);
check_workingset(&array, 64);