Re: [bug] userspace hitting sporadic SIGBUS on xfs (Power9, ppc64le), v4.19 and later

[Christoph Hellwig]

Please try the patch below:

diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
index 512856a88106..340c15400423 100644
--- a/fs/iomap/buffered-io.c
+++ b/fs/iomap/buffered-io.c
@@ -28,6 +28,7 @@
 struct iomap_page {
        atomic_t                read_count;
        atomic_t                write_count;
+       spinlock_t              uptodate_lock;
        DECLARE_BITMAP(uptodate, PAGE_SIZE / 512);
 };
 
@@ -51,6 +52,7 @@ iomap_page_create(struct inode *inode, struct page *page)
        iop = kmalloc(sizeof(*iop), GFP_NOFS | __GFP_NOFAIL);
        atomic_set(&iop->read_count, 0);
        atomic_set(&iop->write_count, 0);
+       spin_lock_init(&iop->uptodate_lock);
        bitmap_zero(iop->uptodate, PAGE_SIZE / SECTOR_SIZE);
 
        /*
@@ -139,25 +141,38 @@ iomap_adjust_read_range(struct inode *inode, struct 
iomap_page *iop,
 }
 
 static void
-iomap_set_range_uptodate(struct page *page, unsigned off, unsigned len)
+iomap_iop_set_range_uptodate(struct page *page, unsigned off, unsigned len)
 {
        struct iomap_page *iop = to_iomap_page(page);
        struct inode *inode = page->mapping->host;
        unsigned first = off >> inode->i_blkbits;
        unsigned last = (off + len - 1) >> inode->i_blkbits;
-       unsigned int i;
        bool uptodate = true;
+       unsigned long flags;
+       unsigned int i;
 
-       if (iop) {
-               for (i = 0; i < PAGE_SIZE / i_blocksize(inode); i++) {
-                       if (i >= first && i <= last)
-                               set_bit(i, iop->uptodate);
-                       else if (!test_bit(i, iop->uptodate))
-                               uptodate = false;
-               }
+       spin_lock_irqsave(&iop->uptodate_lock, flags);
+       for (i = 0; i < PAGE_SIZE / i_blocksize(inode); i++) {
+               if (i >= first && i <= last)
+                       set_bit(i, iop->uptodate);
+               else if (!test_bit(i, iop->uptodate))
+                       uptodate = false;
        }
 
-       if (uptodate && !PageError(page))
+       if (uptodate)
+               SetPageUptodate(page);
+       spin_unlock_irqrestore(&iop->uptodate_lock, flags);
+}
+
+static void
+iomap_set_range_uptodate(struct page *page, unsigned off, unsigned len)
+{
+       if (PageError(page))
+               return;
+
+       if (page_has_private(page))
+               iomap_iop_set_range_uptodate(page, off, len);
+       else
                SetPageUptodate(page);
 }