Messages in this thread Patch in this message | | | From | Valerie Aurora <> | Subject | [PATCH 09/34] union-mount: Add two superblock fields for union mounts | Date | Thu, 16 Sep 2010 15:12:00 -0700 |
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Add two fields to struct super_block to support union mounts. s_union_lower_mnts is a pointer to a cloned vfsmount tree of all the lower (read-only) mounts unioned with the topmost (read-write) vfsmount. These mounts may have submounts which will also be unioned; hence we copy the entire vfsmount tree, not just the root vfsmounts. s_union_count is the number of lower mounts unioned at the root of the file system. This count is the maximum number of directories that will ever be unioned with a single directory. We use it to allocate a union stack of the correct size for each directory.
Signed-off-by: Valerie Aurora <vaurora@redhat.com> --- include/linux/fs.h | 12 ++++++++++++ 1 files changed, 12 insertions(+), 0 deletions(-)
diff --git a/include/linux/fs.h b/include/linux/fs.h index 2e3d745..5e35b03 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -1397,6 +1397,18 @@ struct super_block { * Decremented by free_vfsmnt() if MNT_HARD_READONLY is set. */ int s_hard_readonly_users; + + /* + * Root of the private cloned vfsmount tree of the read-only + * mounts in this union (set in topmost vfsmount only) + */ + struct vfsmount *s_union_lower_mnts; + + /* + * Number of layers in this union, not counting the topmost or + * submounts. + */ + unsigned int s_union_count; }; extern struct timespec current_fs_time(struct super_block *sb); -- 1.6.3.3
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