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NAME

     VOP_RENAME - rename a file

SYNOPSIS

     #include <sys/param.h>
     #include <sys/vnode.h>

     int
     VOP_RENAME(struct vnode *fdvp, struct vnode *fvp,
             struct componentname *fcnp, struct vnode *tdvp,
             struct vnode *tvp, struct componentname *tcnp);

DESCRIPTION

     This renames a file and possibly changes its parent directory.  If the
     destination object exists, it will be removed first.

     Its arguments are:

     fdvp  The vnode of the old parent directory.

     fvp   The vnode of the file to be renamed.

     fcnp  Pathname information about the file’s current name.

     tdvp  The vnode of the new parent directory.

     tvp   The vnode of the target file (if it exists).

     tcnp  Pathname information about the file’s new name.

LOCKS

     The source directory and file are unlocked but are expected to have their
     ref count bumped on entry.  The VOP routine is expected to vrele(9) both
     prior to returning.

     The destination directory and file are locked as well as having their ref
     count bumped.  The VOP routine is expected to vput(9) both prior to
     returning.

PSEUDOCODE

     int
     vop_rename(struct vnode *fdvp, struct vnode *fvp, struct componentname *fcnp,
                struct vnode *tdvp, struct vnode *tvp, struct componentname *tcnp)
     {
         int doingdirectory = 0;
         int error = 0;

         /*
          * Check for cross-device rename.
          */
         if (fvp->v_mount != tdvp->v_mount) {
             error = EXDEV;
         abortit:
             if (tdvp == tvp)
                 vrele(tdvp);
             else
                 vput(tdvp);
             if (tvp)
                 vput(tvp);
             vrele(fdvp);
             vrele(fvp);
             return error;
         }

         if (tvp exists and is immutable) {
             error = EPERM;
             goto abortit;
         }

         /*
          * POSIX: "If the old argument and the new argument
          * both refer to links to the same existing file,
          * the rename() function shall return successfully
          * and perform no other action."
          * The upper layers already handle this case.
          */
         KASSERT(fvp != tvp, ("vop_rename: source and destination are the same"));

         if (fvp is immutable) {
             error = EPERM;
             goto abortit;
         }

         error = VOP_LOCK(fvp);
         if (error)
             goto abortit;

         if (vp is a directory) {
             /*
              * Avoid ".", "..", and aliases of "." for obvious reasons.
              */
             if ((fcnp->cn_namelen == 1 && fcnp->cn_nameptr[0] == ’.’)
                 || fdvp == fvp
                 || ((fcnp->cn_flags | tcnp->cn_flags) & ISDOTDOT)) {
                 VOP_UNLOCK(fvp);
                 error = EINVAL;
                 goto abortit;
             }
             doingdirectory = 1;
         }
         vrele(fdvp);

         /*
          * Bump link count on fvp while we are moving stuff around.  If we
          * crash before completing the work, the link count may be wrong
          * but correctable.
          */
         ...;

         /*
          * If ".." must be changed (ie the directory gets a new
          * parent) then the source directory must not be in the
          * directory hierarchy above the target, as this would
          * orphan everything below the source directory. Also
          * the user must have write permission in the source so
          * as to be able to change "..".
          */
         error = VOP_ACCESS(fvp, VWRITE, tcnp->cn_cred, tcnp->cn_thread);
         VOP_UNLOCK(fvp);
         if (doingdirectory && fdvp != tdvp) {
             /*
              * Check for pathname conflict.
              */
             ...;
         }

         /*
          * If the target doesn’t exist, link the target to the source and
          * unlink the source.  Otherwise, rewrite the target directory to
          * reference the source and remove the original entry.
          */
         if (tvp == NULL) {
             /*
              * Account for ".." in new directory.
              */
             if (doingdirectory && fdvp != tdvp) {
                 /*
                  * Increase link count of tdvp.
                  */
                 ...;
             }

             /*
              * Add name in new directory.
              */
             ...;

             if (error) {
                 if (doingdirectory && fdvp != tdvp) {
                     /*
                      * Decrease link count if tdvp.
                      */
                     ...;
                 }
                 goto bad;
             }
             vput(tdvp);
         } else {
             /*
              * Target must be empty if a directory and have no links
              * to it. Also, ensure source and target are compatible
              * (both directories, or both not directories).
              */
             if (tvp is a directory) {
                 if (tvp is not empty) {
                     error = ENOTEMPTY;
                     goto bad;
                 }
                 if (!doingdirectory) {
                     error = ENOTDIR;
                     goto bad;
                 }
                 /*
                  * Update name cache since directory is going away.
                  */
                 cache_purge(tdvp);
             } else if (doingdirectory) {
                 error = ENOTDIR;
                 goto bad;
             }

             /*
              * Change name tcnp in tdvp to point at fvp.
              */
             ...;

             /*
              * If the target directory is in same directory as the source
              * directory, decrement the link count on the parent of the
              * target directory.  This accounts for the fact that a
              * directory links back to its parent with "..".
              */
             if (doingdirectory && fdvp == tdvp) {
                 /*
                  * Decrement link count of tdvp.
                  */
                 ...;
             }
             vput(tdvp);

             /*
              * Decrement the link count of tvp since the directory no
              * longer points at it.
              */
             ...;
             if (doingdirectory) {
                 /*
                  * Clean up the old directory tvp.
                  */
                 ...;
             }
             vput(tvp);
         }

         /*
          * Unlink the source.  If a directory was moved to a new parent,
          * update its ".." entry.  Gobs of ugly UFS code omitted here.
          */
         ...;

     bad:
         if (tvp)
             vput(tvp);
         vput(tdvp);
     out:
         if (VOP_LOCK(fvp) == 0) {
             /*
              * Decrement link count of fvp.
              */
             ...;
             vput(fvp);
         } else
             vrele(fvp);

         return error;
     }

ERRORS

     [EPERM]            The file is immutable.

     [EXDEV]            It is not possible to rename a file between different
                        file systems.

     [EINVAL]           An attempt was made to rename . or .., or to perform
                        an operation which would break the directory tree
                        structure.

     [ENOTDIR]          An attempt was made to rename a directory to a file or
                        vice versa.

     [ENOTEMPTY]        An attempt was made to remove a directory which is not
                        empty.

SEE ALSO

     vnode(9)

AUTHORS

     This manual page was written by Doug Rabson.