1. 20 11月, 2014 1 次提交
  2. 05 11月, 2014 1 次提交
  3. 01 11月, 2014 1 次提交
  4. 29 10月, 2014 3 次提交
  5. 25 10月, 2014 4 次提交
  6. 24 10月, 2014 1 次提交
    • M
      overlay filesystem · e9be9d5e
      Miklos Szeredi 提交于
      Overlayfs allows one, usually read-write, directory tree to be
      overlaid onto another, read-only directory tree.  All modifications
      go to the upper, writable layer.
      
      This type of mechanism is most often used for live CDs but there's a
      wide variety of other uses.
      
      The implementation differs from other "union filesystem"
      implementations in that after a file is opened all operations go
      directly to the underlying, lower or upper, filesystems.  This
      simplifies the implementation and allows native performance in these
      cases.
      
      The dentry tree is duplicated from the underlying filesystems, this
      enables fast cached lookups without adding special support into the
      VFS.  This uses slightly more memory than union mounts, but dentries
      are relatively small.
      
      Currently inodes are duplicated as well, but it is a possible
      optimization to share inodes for non-directories.
      
      Opening non directories results in the open forwarded to the
      underlying filesystem.  This makes the behavior very similar to union
      mounts (with the same limitations vs. fchmod/fchown on O_RDONLY file
      descriptors).
      
      Usage:
      
        mount -t overlayfs overlayfs -olowerdir=/lower,upperdir=/upper/upper,workdir=/upper/work /overlay
      
      The following cotributions have been folded into this patch:
      
      Neil Brown <neilb@suse.de>:
       - minimal remount support
       - use correct seek function for directories
       - initialise is_real before use
       - rename ovl_fill_cache to ovl_dir_read
      
      Felix Fietkau <nbd@openwrt.org>:
       - fix a deadlock in ovl_dir_read_merged
       - fix a deadlock in ovl_remove_whiteouts
      
      Erez Zadok <ezk@fsl.cs.sunysb.edu>
       - fix cleanup after WARN_ON
      
      Sedat Dilek <sedat.dilek@googlemail.com>
       - fix up permission to confirm to new API
      
      Robin Dong <hao.bigrat@gmail.com>
       - fix possible leak in ovl_new_inode
       - create new inode in ovl_link
      
      Andy Whitcroft <apw@canonical.com>
       - switch to __inode_permission()
       - copy up i_uid/i_gid from the underlying inode
      
      AV:
       - ovl_copy_up_locked() - dput(ERR_PTR(...)) on two failure exits
       - ovl_clear_empty() - one failure exit forgetting to do unlock_rename(),
         lack of check for udir being the parent of upper, dropping and regaining
         the lock on udir (which would require _another_ check for parent being
         right).
       - bogus d_drop() in copyup and rename [fix from your mail]
       - copyup/remove and copyup/rename races [fix from your mail]
       - ovl_dir_fsync() leaving ERR_PTR() in ->realfile
       - ovl_entry_free() is pointless - it's just a kfree_rcu()
       - fold ovl_do_lookup() into ovl_lookup()
       - manually assigning ->d_op is wrong.  Just use ->s_d_op.
       [patches picked from Miklos]:
       * copyup/remove and copyup/rename races
       * bogus d_drop() in copyup and rename
      
      Also thanks to the following people for testing and reporting bugs:
      
        Jordi Pujol <jordipujolp@gmail.com>
        Andy Whitcroft <apw@canonical.com>
        Michal Suchanek <hramrach@centrum.cz>
        Felix Fietkau <nbd@openwrt.org>
        Erez Zadok <ezk@fsl.cs.sunysb.edu>
        Randy Dunlap <rdunlap@xenotime.net>
      Signed-off-by: NMiklos Szeredi <mszeredi@suse.cz>
      e9be9d5e