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remarkable-linux/fs/Kconfig
Miklos Szeredi e9be9d5e76 overlay filesystem 
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: Miklos Szeredi <mszeredi@suse.cz>
2014-10-24 00:14:38 +02:00

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#
# File system configuration
#
menu "File systems"
# Use unaligned word dcache accesses
config DCACHE_WORD_ACCESS
bool
if BLOCK
source "fs/ext2/Kconfig"
source "fs/ext3/Kconfig"
source "fs/ext4/Kconfig"
config FS_XIP
# execute in place
bool
depends on EXT2_FS_XIP
default y
source "fs/jbd/Kconfig"
source "fs/jbd2/Kconfig"
config FS_MBCACHE
# Meta block cache for Extended Attributes (ext2/ext3/ext4)
tristate
default y if EXT2_FS=y && EXT2_FS_XATTR
default y if EXT3_FS=y && EXT3_FS_XATTR
default y if EXT4_FS=y
default m if EXT2_FS_XATTR || EXT3_FS_XATTR || EXT4_FS
source "fs/reiserfs/Kconfig"
source "fs/jfs/Kconfig"
source "fs/xfs/Kconfig"
source "fs/gfs2/Kconfig"
source "fs/ocfs2/Kconfig"
source "fs/btrfs/Kconfig"
source "fs/nilfs2/Kconfig"
endif # BLOCK
# Posix ACL utility routines
#
# Note: Posix ACLs can be implemented without these helpers. Never use
# this symbol for ifdefs in core code.
#
config FS_POSIX_ACL
def_bool n
config EXPORTFS
tristate
config FILE_LOCKING
bool "Enable POSIX file locking API" if EXPERT
default y
help
This option enables standard file locking support, required
for filesystems like NFS and for the flock() system
call. Disabling this option saves about 11k.
source "fs/notify/Kconfig"
source "fs/quota/Kconfig"
source "fs/autofs4/Kconfig"
source "fs/fuse/Kconfig"
source "fs/overlayfs/Kconfig"
menu "Caches"
source "fs/fscache/Kconfig"
source "fs/cachefiles/Kconfig"
endmenu
if BLOCK
menu "CD-ROM/DVD Filesystems"
source "fs/isofs/Kconfig"
source "fs/udf/Kconfig"
endmenu
endif # BLOCK
if BLOCK
menu "DOS/FAT/NT Filesystems"
source "fs/fat/Kconfig"
source "fs/ntfs/Kconfig"
endmenu
endif # BLOCK
menu "Pseudo filesystems"
source "fs/proc/Kconfig"
source "fs/kernfs/Kconfig"
source "fs/sysfs/Kconfig"
config TMPFS
bool "Tmpfs virtual memory file system support (former shm fs)"
depends on SHMEM
help
Tmpfs is a file system which keeps all files in virtual memory.
Everything in tmpfs is temporary in the sense that no files will be
created on your hard drive. The files live in memory and swap
space. If you unmount a tmpfs instance, everything stored therein is
lost.
See <file:Documentation/filesystems/tmpfs.txt> for details.
config TMPFS_POSIX_ACL
bool "Tmpfs POSIX Access Control Lists"
depends on TMPFS
select TMPFS_XATTR
select FS_POSIX_ACL
help
POSIX Access Control Lists (ACLs) support additional access rights
for users and groups beyond the standard owner/group/world scheme,
and this option selects support for ACLs specifically for tmpfs
filesystems.
If you've selected TMPFS, it's possible that you'll also need
this option as there are a number of Linux distros that require
POSIX ACL support under /dev for certain features to work properly.
For example, some distros need this feature for ALSA-related /dev
files for sound to work properly. In short, if you're not sure,
say Y.
To learn more about Access Control Lists, visit the POSIX ACLs for
Linux website <http://acl.bestbits.at/>.
config TMPFS_XATTR
bool "Tmpfs extended attributes"
depends on TMPFS
default n
help
Extended attributes are name:value pairs associated with inodes by
the kernel or by users (see the attr(5) manual page, or visit
<http://acl.bestbits.at/> for details).
Currently this enables support for the trusted.* and
security.* namespaces.
You need this for POSIX ACL support on tmpfs.
If unsure, say N.
config HUGETLBFS
bool "HugeTLB file system support"
depends on X86 || IA64 || SPARC64 || (S390 && 64BIT) || \
SYS_SUPPORTS_HUGETLBFS || BROKEN
help
hugetlbfs is a filesystem backing for HugeTLB pages, based on
ramfs. For architectures that support it, say Y here and read
<file:Documentation/vm/hugetlbpage.txt> for details.
If unsure, say N.
config HUGETLB_PAGE
def_bool HUGETLBFS
source "fs/configfs/Kconfig"
endmenu
menuconfig MISC_FILESYSTEMS
bool "Miscellaneous filesystems"
default y
---help---
Say Y here to get to see options for various miscellaneous
filesystems, such as filesystems that came from other
operating systems.
This option alone does not add any kernel code.
If you say N, all options in this submenu will be skipped and
disabled; if unsure, say Y here.
if MISC_FILESYSTEMS
source "fs/adfs/Kconfig"
source "fs/affs/Kconfig"
source "fs/ecryptfs/Kconfig"
source "fs/hfs/Kconfig"
source "fs/hfsplus/Kconfig"
source "fs/befs/Kconfig"
source "fs/bfs/Kconfig"
source "fs/efs/Kconfig"
source "fs/jffs2/Kconfig"
# UBIFS File system configuration
source "fs/ubifs/Kconfig"
source "fs/logfs/Kconfig"
source "fs/cramfs/Kconfig"
source "fs/squashfs/Kconfig"
source "fs/freevxfs/Kconfig"
source "fs/minix/Kconfig"
source "fs/omfs/Kconfig"
source "fs/hpfs/Kconfig"
source "fs/qnx4/Kconfig"
source "fs/qnx6/Kconfig"
source "fs/romfs/Kconfig"
source "fs/pstore/Kconfig"
source "fs/sysv/Kconfig"
source "fs/ufs/Kconfig"
source "fs/exofs/Kconfig"
source "fs/f2fs/Kconfig"
source "fs/efivarfs/Kconfig"
endif # MISC_FILESYSTEMS
source "fs/exofs/Kconfig.ore"
menuconfig NETWORK_FILESYSTEMS
bool "Network File Systems"
default y
depends on NET
---help---
Say Y here to get to see options for network filesystems and
filesystem-related networking code, such as NFS daemon and
RPCSEC security modules.
This option alone does not add any kernel code.
If you say N, all options in this submenu will be skipped and
disabled; if unsure, say Y here.
if NETWORK_FILESYSTEMS
source "fs/nfs/Kconfig"
source "fs/nfsd/Kconfig"
config GRACE_PERIOD
tristate
config LOCKD
tristate
depends on FILE_LOCKING
select GRACE_PERIOD
config LOCKD_V4
bool
depends on NFSD_V3 || NFS_V3
depends on FILE_LOCKING
default y
config NFS_ACL_SUPPORT
tristate
select FS_POSIX_ACL
config NFS_COMMON
bool
depends on NFSD || NFS_FS || LOCKD
default y
source "net/sunrpc/Kconfig"
source "fs/ceph/Kconfig"
source "fs/cifs/Kconfig"
source "fs/ncpfs/Kconfig"
source "fs/coda/Kconfig"
source "fs/afs/Kconfig"
source "fs/9p/Kconfig"
endif # NETWORK_FILESYSTEMS
source "fs/nls/Kconfig"
source "fs/dlm/Kconfig"
endmenu
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