From: Mikulas Patocka mpatocka@redhat.com
commit b17164e258e3888d376a7434415013175d637377 upstream.
When running in a dax mode, if the user maps a page with MAP_PRIVATE and PROT_WRITE, the xfs filesystem would incorrectly update ctime and mtime when the user hits a COW fault.
This breaks building of the Linux kernel. How to reproduce:
1. extract the Linux kernel tree on dax-mounted xfs filesystem 2. run make clean 3. run make -j12 4. run make -j12
at step 4, make would incorrectly rebuild the whole kernel (although it was already built in step 3).
The reason for the breakage is that almost all object files depend on objtool. When we run objtool, it takes COW page fault on its .data section, and these faults will incorrectly update the timestamp of the objtool binary. The updated timestamp causes make to rebuild the whole tree.
Signed-off-by: Mikulas Patocka mpatocka@redhat.com Cc: stable@vger.kernel.org Signed-off-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- fs/xfs/xfs_file.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-)
--- a/fs/xfs/xfs_file.c +++ b/fs/xfs/xfs_file.c @@ -1220,6 +1220,14 @@ __xfs_filemap_fault( return ret; }
+static inline bool +xfs_is_write_fault( + struct vm_fault *vmf) +{ + return (vmf->flags & FAULT_FLAG_WRITE) && + (vmf->vma->vm_flags & VM_SHARED); +} + static vm_fault_t xfs_filemap_fault( struct vm_fault *vmf) @@ -1227,7 +1235,7 @@ xfs_filemap_fault( /* DAX can shortcut the normal fault path on write faults! */ return __xfs_filemap_fault(vmf, PE_SIZE_PTE, IS_DAX(file_inode(vmf->vma->vm_file)) && - (vmf->flags & FAULT_FLAG_WRITE)); + xfs_is_write_fault(vmf)); }
static vm_fault_t @@ -1240,7 +1248,7 @@ xfs_filemap_huge_fault(
/* DAX can shortcut the normal fault path on write faults! */ return __xfs_filemap_fault(vmf, pe_size, - (vmf->flags & FAULT_FLAG_WRITE)); + xfs_is_write_fault(vmf)); }
static vm_fault_t