Nfs readdir

From Linux NFS

Revision as of 19:51, 6 July 2010

nfs_readdir()

• fs/nfs/dir.c
• dentry defined in include/linux/dcache.h
• file defined in include/linux/fs.h
• path defined in include/linux/path.h
• nfs_entry defined in /include/linux/nfs_xdr.h

• There is a weakness with the current caching method. Right now, xdr objects are being stored in the cache so reading from the cache requires translating an xdr object into a dentry. This is more natural to use, especially at this point in the kernel.

• make a new dentry: my_entry
  • set the cookie to the previous file, allocate a file handle and attribute struct, mark that we are not at the end of the file
  • If allocations failed, goto out_alloc_failed

• Block silly renames from running

• call nfs_revalidate_mapping (fs/nfs/inode.c) to validate the page cache
  • if there is an error revalidating the cache, goto out
  • if the directory has changed (mtime different) then cache can be cleared

• Begin a loop over directory entries

• while we have not reached the end of the directory file:
  • Search the page cache for the requested page (dir.c: readdir_search_pagecache)
  • if searching results in a bad cookie (EBADCOOKIE), it could mean that we are at the end of the directory or that the file has been deleted
    • ask the server for the next file and add to the page cache using filldir (dir.c: uncached_readdir)
    • if the response is good, go to the beginning of the while loop and look up the next entry, otherwise break out of the loop
  • if the server's response is bigger than the size limit set by the client (ETOOSMALL) and if we are doing a readdir plus
    • clear the "NFS_INO_ADVISE_RDPLUS" flag contained in the nfs_inode
    • "zap" the cache (invalidate the nfs_inode)
  • if res indicates any other error, break out of the loop
  • add the page to the cache
    • break out of the loop if there is a problem adding the page to the cache

• out:
  • unblock (allow) silly renames
  • set response is non zero, set it equal to zero

• out_alloc_failed:
  • free file handle and attr structs in my_entry
  • print a message stating what is being returned
  • return the response code