1 files changed, 34 insertions, 6 deletions

diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index ca46a529d56b..361535c71c0f 100644
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -1106,6 +1106,25 @@ void btrfs_check_nocow_unlock(struct btrfs_inode *inode)
 	btrfs_drew_write_unlock(&inode->root->snapshot_lock);
 }
 
+static void update_time_for_write(struct inode *inode)
+{
+	struct timespec64 now, ctime;
+
+	if (IS_NOCMTIME(inode))
+		return;
+
+	now = current_time(inode);
+	if (!timespec64_equal(&inode->i_mtime, &now))
+		inode->i_mtime = now;
+
+	ctime = inode_get_ctime(inode);
+	if (!timespec64_equal(&ctime, &now))
+		inode_set_ctime_to_ts(inode, now);
+
+	if (IS_I_VERSION(inode))
+		inode_inc_iversion(inode);
+}
+
 static int btrfs_write_check(struct kiocb *iocb, struct iov_iter *from,
 			     size_t count)
 {
@@ -1137,10 +1156,7 @@ static int btrfs_write_check(struct kiocb *iocb, struct iov_iter *from,
 	 * need to start yet another transaction to update the inode as we will
 	 * update the inode when we finish writing whatever data we write.
 	 */
-	if (!IS_NOCMTIME(inode)) {
-		inode->i_mtime = inode_set_ctime_current(inode);
-		inode_inc_iversion(inode);
-	}
+	update_time_for_write(inode);
 
 	start_pos = round_down(pos, fs_info->sectorsize);
 	oldsize = i_size_read(inode);
@@ -1451,8 +1467,13 @@ static ssize_t btrfs_direct_write(struct kiocb *iocb, struct iov_iter *from)
 	if (iocb->ki_flags & IOCB_NOWAIT)
 		ilock_flags |= BTRFS_ILOCK_TRY;
 
-	/* If the write DIO is within EOF, use a shared lock */
-	if (iocb->ki_pos + iov_iter_count(from) <= i_size_read(inode))
+	/*
+	 * If the write DIO is within EOF, use a shared lock and also only if
+	 * security bits will likely not be dropped by file_remove_privs() called
+	 * from btrfs_write_check(). Either will need to be rechecked after the
+	 * lock was acquired.
+	 */
+	if (iocb->ki_pos + iov_iter_count(from) <= i_size_read(inode) && IS_NOSEC(inode))
 		ilock_flags |= BTRFS_ILOCK_SHARED;
 
 relock:
@@ -1460,6 +1481,13 @@ relock:
 	if (err < 0)
 		return err;
 
+	/* Shared lock cannot be used with security bits set. */
+	if ((ilock_flags & BTRFS_ILOCK_SHARED) && !IS_NOSEC(inode)) {
+		btrfs_inode_unlock(BTRFS_I(inode), ilock_flags);
+		ilock_flags &= ~BTRFS_ILOCK_SHARED;
+		goto relock;
+	}
+
 	err = generic_write_checks(iocb, from);
 	if (err <= 0) {
 		btrfs_inode_unlock(BTRFS_I(inode), ilock_flags);