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authorMatthew Wilcox (Oracle) <willy@infradead.org>2020-10-15 20:05:13 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2020-10-16 11:11:15 -0700
commit57417cebc96b57122a2207fc84a6077d20c84b4b (patch)
tree4a15c75bcc56f0c5392393a2d0672e4acc539a9e /include/linux/xarray.h
parentf14312e1ed1e40dfed38bb70eb9a71d97a6b60f4 (diff)
XArray: add xa_get_order
Patch series "Fix read-only THP for non-tmpfs filesystems". As described more verbosely in the [3/3] changelog, we can inadvertently put an order-0 page in the page cache which occupies 512 consecutive entries. Users are running into this if they enable the READ_ONLY_THP_FOR_FS config option; see https://bugzilla.kernel.org/show_bug.cgi?id=206569 and Qian Cai has also reported it here: https://lore.kernel.org/lkml/20200616013309.GB815@lca.pw/ This is a rather intrusive way of fixing the problem, but has the advantage that I've actually been testing it with the THP patches, which means that it sees far more use than it does upstream -- indeed, Song has been entirely unable to reproduce it. It also has the advantage that it removes a few patches from my gargantuan backlog of THP patches. This patch (of 3): This function returns the order of the entry at the index. We need this because there isn't space in the shadow entry to encode its order. [akpm@linux-foundation.org: export xa_get_order to modules] 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/20200903183029.14930-1-willy@infradead.org Link: https://lkml.kernel.org/r/20200903183029.14930-2-willy@infradead.org Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include/linux/xarray.h')
-rw-r--r--include/linux/xarray.h9
1 files changed, 9 insertions, 0 deletions
diff --git a/include/linux/xarray.h b/include/linux/xarray.h
index b4d70e7568b2..5b7f4ebcf4ff 100644
--- a/include/linux/xarray.h
+++ b/include/linux/xarray.h
@@ -1505,6 +1505,15 @@ void xas_pause(struct xa_state *);
void xas_create_range(struct xa_state *);
+#ifdef CONFIG_XARRAY_MULTI
+int xa_get_order(struct xarray *, unsigned long index);
+#else
+static inline int xa_get_order(struct xarray *xa, unsigned long index)
+{
+ return 0;
+}
+#endif
+
/**
* xas_reload() - Refetch an entry from the xarray.
* @xas: XArray operation state.