Merge tag 'ext4_for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4

Pull ext4 updates from Ted Ts'o:
 "Scalability improvements when allocating inodes, and some
  miscellaneous bug fixes and cleanups"

* tag 'ext4_for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4:
  ext4: avoid Y2038 overflow in recently_deleted()
  ext4: fix fault handling when mounted with -o dax,ro
  ext4: fix quota inconsistency during orphan cleanup for read-only mounts
  ext4: fix incorrect quotaoff if the quota feature is enabled
  ext4: remove useless test and assignment in strtohash functions
  ext4: backward compatibility support for Lustre ea_inode implementation
  ext4: remove timebomb in ext4_decode_extra_time()
  ext4: use sizeof(*ptr)
  ext4: in ext4_seek_{hole,data}, return -ENXIO for negative offsets
  ext4: reduce lock contention in __ext4_new_inode
  ext4: cleanup goto next group
  ext4: do not unnecessarily allocate buffer in recently_deleted()

1 files changed, 16 insertions, 3 deletions

diff --git a/fs/ext4/file.c b/fs/ext4/file.c
index 0d7cf0cc9b87..197653ea6041 100644
--- a/fs/ext4/file.c
+++ b/fs/ext4/file.c
@@ -279,7 +279,20 @@ static int ext4_dax_huge_fault(struct vm_fault *vmf,
 	handle_t *handle = NULL;
 	struct inode *inode = file_inode(vmf->vma->vm_file);
 	struct super_block *sb = inode->i_sb;
-	bool write = vmf->flags & FAULT_FLAG_WRITE;
+
+	/*
+	 * We have to distinguish real writes from writes which will result in a
+	 * COW page; COW writes should *not* poke the journal (the file will not
+	 * be changed). Doing so would cause unintended failures when mounted
+	 * read-only.
+	 *
+	 * We check for VM_SHARED rather than vmf->cow_page since the latter is
+	 * unset for pe_size != PE_SIZE_PTE (i.e. only in do_cow_fault); for
+	 * other sizes, dax_iomap_fault will handle splitting / fallback so that
+	 * we eventually come back with a COW page.
+	 */
+	bool write = (vmf->flags & FAULT_FLAG_WRITE) &&
+		(vmf->vma->vm_flags & VM_SHARED);
 
 	if (write) {
 		sb_start_pagefault(sb);
@@ -595,7 +608,7 @@ static loff_t ext4_seek_data(struct file *file, loff_t offset, loff_t maxsize)
 	inode_lock(inode);
 
 	isize = i_size_read(inode);
-	if (offset >= isize) {
+	if (offset < 0 || offset >= isize) {
 		inode_unlock(inode);
 		return -ENXIO;
 	}
@@ -658,7 +671,7 @@ static loff_t ext4_seek_hole(struct file *file, loff_t offset, loff_t maxsize)
 	inode_lock(inode);
 
 	isize = i_size_read(inode);
-	if (offset >= isize) {
+	if (offset < 0 || offset >= isize) {
 		inode_unlock(inode);
 		return -ENXIO;
 	}