From 0e40de0338d005f73d46898a21544cd26f01b4ce Mon Sep 17 00:00:00 2001 From: Matthew Wilcox Date: Fri, 16 Nov 2018 15:19:13 -0500 Subject: [PATCH] dax: Fix huge page faults Using xas_load() with a PMD-sized xa_state would work if either a PMD-sized entry was present or a PTE sized entry was present in the first 64 entries (of the 512 PTEs in a PMD on x86). If there was no PTE in the first 64 entries, grab_mapping_entry() would believe there were no entries present, allocate a PMD-sized entry and overwrite the PTE in the page cache. Use xas_find_conflict() instead which turns out to simplify both get_unlocked_entry() and grab_mapping_entry(). Also remove a WARN_ON_ONCE from grab_mapping_entry() as it will have already triggered in get_unlocked_entry(). Fixes: cfc93c6c6c96 ("dax: Convert dax_insert_pfn_mkwrite to XArray") Signed-off-by: Matthew Wilcox --- fs/dax.c | 12 ++++-------- 1 file changed, 4 insertions(+), 8 deletions(-) diff --git a/fs/dax.c b/fs/dax.c index 5426252..cf2394e 100644 --- a/fs/dax.c +++ b/fs/dax.c @@ -216,9 +216,8 @@ static void *get_unlocked_entry(struct xa_state *xas) ewait.wait.func = wake_exceptional_entry_func; for (;;) { - entry = xas_load(xas); - if (!entry || xa_is_internal(entry) || - WARN_ON_ONCE(!xa_is_value(entry)) || + entry = xas_find_conflict(xas); + if (!entry || WARN_ON_ONCE(!xa_is_value(entry)) || !dax_is_locked(entry)) return entry; @@ -458,11 +457,9 @@ static void *grab_mapping_entry(struct xa_state *xas, retry: xas_lock_irq(xas); entry = get_unlocked_entry(xas); - if (xa_is_internal(entry)) - goto fallback; if (entry) { - if (WARN_ON_ONCE(!xa_is_value(entry))) { + if (!xa_is_value(entry)) { xas_set_err(xas, EIO); goto out_unlock; } @@ -1641,8 +1638,7 @@ dax_insert_pfn_mkwrite(struct vm_fault *vmf, pfn_t pfn, unsigned int order) /* Did we race with someone splitting entry or so? */ if (!entry || (order == 0 && !dax_is_pte_entry(entry)) || - (order == PMD_ORDER && (xa_is_internal(entry) || - !dax_is_pmd_entry(entry)))) { + (order == PMD_ORDER && !dax_is_pmd_entry(entry))) { put_unlocked_entry(&xas, entry); xas_unlock_irq(&xas); trace_dax_insert_pfn_mkwrite_no_entry(mapping->host, vmf, -- 2.7.4