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XArray: Fix xa_find_after with multi-index entries

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If the entry is of an order which is a multiple of XA_CHUNK_SIZE,
the current detection of sibling entries does not work.  Factor out
an xas_sibling() function to make xa_find_after() a little more
understandable, and write a new implementation that doesn't suffer from
the same bug.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: stable@vger.kernel.org
This commit is contained in:
Matthew Wilcox (Oracle) 2020-01-17 22:00:41 -05:00
parent 430f24f94c
commit 19c30f4dd0
2 changed files with 32 additions and 20 deletions
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20
lib/xarray.c
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@ -1826,6 +1826,17 @@ void *xa_find(struct xarray *xa, unsigned long *indexp,
}
EXPORT_SYMBOL(xa_find);
static bool xas_sibling(struct xa_state *xas)
{
struct xa_node *node = xas->xa_node;
unsigned long mask;
if (!node)
return false;
mask = (XA_CHUNK_SIZE << node->shift) - 1;
return (xas->xa_index & mask) > (xas->xa_offset << node->shift);
}
/**
* xa_find_after() - Search the XArray for a present entry.
* @xa: XArray.
@ -1860,13 +1871,8 @@ void *xa_find_after(struct xarray *xa, unsigned long *indexp,
entry = xas_find(&xas, max);
if (xas.xa_node == XAS_BOUNDS)
break;
if (xas.xa_shift) {
if (xas.xa_index & ((1UL << xas.xa_shift) - 1))
continue;
} else {
if (xas.xa_offset < (xas.xa_index & XA_CHUNK_MASK))
continue;
}
if (xas_sibling(&xas))
continue;
if (!xas_retry(&xas, entry))
break;
}