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    Subject[PATCH 02/25] rearrange may_open() to be r/o friendly
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    may_open() calls vfs_permission() before it does checks for
    IS_RDONLY(inode). It checks _again_ inside of vfs_permission().

    The check inside of vfs_permission() is going away eventually.
    With the mnt_want/drop_write() functions, all of the r/o
    checks (except for this one) are consistently done before
    calling permission(). Because of this, I'd like to use
    permission() to hold a debugging check to make sure that
    the mnt_want/drop_write() calls are actually being made.

    So, to do this:
    1. remove the IS_RDONLY() check from permission()
    2. enforce that you must mnt_want_write() before
    even calling permission()
    3. actually add the debugging check to permission()

    We need to rearrange may_open() to do r/o checks
    before calling permission(). Here's the patch.

    Signed-off-by: Dave Hansen <haveblue@us.ibm.com>
    ---

    lxc-dave/fs/namei.c | 8 ++++----
    1 file changed, 4 insertions(+), 4 deletions(-)

    diff -puN fs/namei.c~rearrange-permission-and-ro-checks-in-may_open fs/namei.c
    --- lxc/fs/namei.c~rearrange-permission-and-ro-checks-in-may_open 2007-09-20 12:16:09.000000000 -0700
    +++ lxc-dave/fs/namei.c 2007-09-20 12:16:09.000000000 -0700
    @@ -1579,10 +1579,6 @@ int may_open(struct nameidata *nd, int a
    if (S_ISDIR(inode->i_mode) && (flag & FMODE_WRITE))
    return -EISDIR;

    - error = vfs_permission(nd, acc_mode);
    - if (error)
    - return error;
    -
    /*
    * FIFO's, sockets and device files are special: they don't
    * actually live on the filesystem itself, and as such you
    @@ -1597,6 +1593,10 @@ int may_open(struct nameidata *nd, int a
    flag &= ~O_TRUNC;
    } else if (IS_RDONLY(inode) && (flag & FMODE_WRITE))
    return -EROFS;
    +
    + error = vfs_permission(nd, acc_mode);
    + if (error)
    + return error;
    /*
    * An append-only file must be opened in append mode for writing.
    */
    _
    -
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