tmakin/ack-tegra
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

XArray: Do not return sibling entries from xa_load()

Browse Source 
It is possible for xa_load() to observe a sibling entry pointing to
another sibling entry.  An example:

Thread A:		Thread B:
			xa_store_range(xa, entry, 188, 191, gfp);
xa_load(xa, 191);
entry = xa_entry(xa, node, 63);
[entry is a sibling of 188]
			xa_store_range(xa, entry, 184, 191, gfp);
if (xa_is_sibling(entry))
offset = xa_to_sibling(entry);
entry = xa_entry(xas->xa, node, offset);
[entry is now a sibling of 184]

It is sufficient to go around this loop until we hit a non-sibling entry.
Sibling entries always point earlier in the node, so we are guaranteed
to terminate this search.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Fixes: 6b24ca4a1a ("mm: Use multi-index entries in the page cache")
Cc: stable@vger.kernel.org
This commit is contained in:
Matthew Wilcox (Oracle)
2023-07-26 22:58:17 -04:00
parent f837f0a3c9
commit cbc0285433
2 changed files with 67 additions and 3 deletions
Download Patch File Download Diff File Expand all files Collapse all files
lib/xarray.c
+1 -1
View File
@@ -206,7 +206,7 @@ static void *xas_descend(struct xa_state *xas, struct xa_node *node)
void *entry = xa_entry(xas->xa, node, offset);
xas->xa_node = node;
if (xa_is_sibling(entry)) {
while (xa_is_sibling(entry)) {
offset = xa_to_sibling(entry);
entry = xa_entry(xas->xa, node, offset);
if (node->shift && xa_is_node(entry))