nilfs2: do not acquire rwsem in nilfs_bmap_write()

It is now clear that nilfs_bmap_write() is only used to finalize logs
written to disk.  Concurrent bmap modification operations are not
performed on bmaps in this context.  Additionally, this function does not
modify data used in read-only operations such as bmap lookups.

Therefore, there is no need to acquire bmap->b_sem in nilfs_bmap_write(),
so delete it.

Link: https://lkml.kernel.org/r/20240122140202.6950-10-konishi.ryusuke@gmail.comSigned-off-by: Ryusuke Konishi <konishi.ryusuke@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

fs/nilfs2/bmap.c

@@ -548,13 +548,10 @@ int nilfs_bmap_read(struct nilfs_bmap *bmap, struct nilfs_inode *raw_inode)
  */
 void nilfs_bmap_write(struct nilfs_bmap *bmap, struct nilfs_inode *raw_inode)
 {
-	down_write(&bmap->b_sem);
 	memcpy(raw_inode->i_bmap, bmap->b_u.u_data,
 	       NILFS_INODE_BMAP_SIZE * sizeof(__le64));
 	if (bmap->b_inode->i_ino == NILFS_DAT_INO)
 		bmap->b_last_allocated_ptr = NILFS_BMAP_NEW_PTR_INIT;
-
-	up_write(&bmap->b_sem);
 }
 
 void nilfs_bmap_init_gc(struct nilfs_bmap *bmap)