If a dax buffer from a device that does not map pages is passed to read(2) or write(2) as a target for direct-I/O it triggers SIGBUS. If gdb attempts to examine the contents of a dax buffer from a device that does not map pages it triggers SIGBUS. If fork(2) is called on a process with a dax mapping from a device that does not map pages it triggers SIGBUS. 'struct page' is required otherwise several kernel code paths break in surprising ways. Disable filesystem-dax on devices that do not map pages.
Cc: Jan Kara <[email protected]> Cc: Jeff Moyer <[email protected]> Cc: Christoph Hellwig <[email protected]> Cc: Ross Zwisler <[email protected]> Signed-off-by: Dan Williams <[email protected]> --- drivers/dax/super.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/drivers/dax/super.c b/drivers/dax/super.c index b0cc8117eebe..491d4859c644 100644 --- a/drivers/dax/super.c +++ b/drivers/dax/super.c @@ -15,6 +15,7 @@ #include <linux/mount.h> #include <linux/magic.h> #include <linux/genhd.h> +#include <linux/pfn_t.h> #include <linux/cdev.h> #include <linux/hash.h> #include <linux/slab.h> @@ -123,6 +124,12 @@ int __bdev_dax_supported(struct super_block *sb, int blocksize) return len < 0 ? len : -EIO; } + if (!pfn_t_has_page(pfn)) { + pr_debug("VFS (%s): error: dax support not enabled\n", + sb->s_id); + return -EOPNOTSUPP; + } + return 0; } EXPORT_SYMBOL_GPL(__bdev_dax_supported); _______________________________________________ Linux-nvdimm mailing list [email protected] https://lists.01.org/mailman/listinfo/linux-nvdimm
