OpenCloudOS-Kernel/fs/overlayfs/Makefile

# SPDX-License-Identifier: GPL-2.0-only
#
# Makefile for the overlay filesystem.
#

obj-$(CONFIG_OVERLAY_FS) += overlay.o

overlay-objs := super.o namei.o util.o inode.o file.o dir.o readdir.o \
		copy_up.o export.o params.o
treewide: Add SPDX license identifier - Makefile/Kconfig Add SPDX license identifiers to all Make/Kconfig files which: - Have no license information of any form These files fall under the project license, GPL v2 only. The resulting SPDX license identifier is: GPL-2.0-only Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 2019-05-19 20:07:45 +08:00			`# SPDX-License-Identifier: GPL-2.0-only`
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 06:14:38 +08:00			`#`
			`# Makefile for the overlay filesystem.`
			`#`

ovl: rename filesystem type to "overlay" Some distributions carry an "old" format of overlayfs while mainline has a "new" format. The distros will possibly want to keep the old overlayfs alongside the new for compatibility reasons. To make it possible to differentiate the two versions change the name of the new one from "overlayfs" to "overlay". Signed-off-by: Miklos Szeredi <mszeredi@suse.cz> Reported-by: Serge Hallyn <serge.hallyn@ubuntu.com> Cc: Andy Whitcroft <apw@canonical.com> 2014-11-20 23:39:59 +08:00			`obj-$(CONFIG_OVERLAY_FS) += overlay.o`
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 06:14:38 +08:00
ovl: stack file ops Implement file operations on a regular overlay file. The underlying file is opened separately and cached in ->private_data. It might be worth making an exception for such files when accounting in nr_file to confirm to userspace expectations. We are only adding a small overhead (248bytes for the struct file) since the real inode and dentry are pinned by overlayfs anyway. This patch doesn't have any effect, since the vfs will use d_real() to find the real underlying file to open. The patch at the end of the series will actually enable this functionality. AV: make it use open_with_fake_path(), don't mess with override_creds SzM: still need to mess with override_creds() until no fs uses current_cred() in their open method. Signed-off-by: Miklos Szeredi <mszeredi@redhat.com> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk> 2018-07-18 21:44:41 +08:00			`overlay-objs := super.o namei.o util.o inode.o file.o dir.o readdir.o \`
ovl: modify layer parameter parsing We ran into issues where mount(8) passed multiple lower layers as one big string through fsconfig(). But the fsconfig() FSCONFIG_SET_STRING option is limited to 256 bytes in strndup_user(). While this would be fixable by extending the fsconfig() buffer I'd rather encourage users to append layers via multiple fsconfig() calls as the interface allows nicely for this. This has also been requested as a feature before. With this port to the new mount api the following will be possible: fsconfig(fs_fd, FSCONFIG_SET_STRING, "lowerdir", "/lower1", 0); /* set upper layer / fsconfig(fs_fd, FSCONFIG_SET_STRING, "upperdir", "/upper", 0); / append "/lower2", "/lower3", and "/lower4" / fsconfig(fs_fd, FSCONFIG_SET_STRING, "lowerdir", ":/lower2:/lower3:/lower4", 0); / turn index feature on / fsconfig(fs_fd, FSCONFIG_SET_STRING, "index", "on", 0); / append "/lower5" / fsconfig(fs_fd, FSCONFIG_SET_STRING, "lowerdir", ":/lower5", 0); Specifying ':' would have been rejected so this isn't a regression. And we can't simply use "lowerdir=/lower" to append on top of existing layers as "lowerdir=/lower,lowerdir=/other-lower" would make "/other-lower" the only lower layer so we'd break uapi if we changed this. So the ':' prefix seems a good compromise. Users can choose to specify multiple layers at once or individual layers. A layer is appended if it starts with ":". This requires that the user has already added at least one layer before. If lowerdir is specified again without a leading ":" then all previous layers are dropped and replaced with the new layers. If lowerdir is specified and empty than all layers are simply dropped. An additional change is that overlayfs will now parse and resolve layers right when they are specified in fsconfig() instead of deferring until super block creation. This allows users to receive early errors. It also allows users to actually use up to 500 layers something which was theoretically possible but ended up not working due to the mount option string passed via mount(2) being too large. This also allows a more privileged process to set config options for a lesser privileged process as the creds for fsconfig() and the creds for fsopen() can differ. We could restrict that they match by enforcing that the creds of fsopen() and fsconfig() match but I don't see why that needs to be the case and allows for a good delegation mechanism. Plus, in the future it means we're able to extend overlayfs mount options and allow users to specify layers via file descriptors instead of paths: fsconfig(FSCONFIG_SET_PATH{_EMPTY}, "lowerdir", "lower1", dirfd); / append / fsconfig(FSCONFIG_SET_PATH{_EMPTY}, "lowerdir", "lower2", dirfd); / append / fsconfig(FSCONFIG_SET_PATH{_EMPTY}, "lowerdir", "lower3", dirfd); / clear all layers specified until now */ fsconfig(FSCONFIG_SET_STRING, "lowerdir", NULL, 0); This would be especially nice if users create an overlayfs mount on top of idmapped layers or just in general private mounts created via open_tree(OPEN_TREE_CLONE). Those mounts would then never have to appear anywhere in the filesystem. But for now just do the minimal thing. We should probably aim to move more validation into ovl_fs_parse_param() so users get errors before fsconfig(FSCONFIG_CMD_CREATE). But that can be done in additional patches later. This is now also rebased on top of the lazy lowerdata lookup which allows the specificatin of data only layers using the new "::" syntax. The rules are simple. A data only layers cannot be followed by any regular layers and data layers must be preceeded by at least one regular layer. Parsing the lowerdir mount option must change because of this. The original patchset used the old lowerdir parsing function to split a lowerdir mount option string such as: lowerdir=/lower1:/lower2::/lower3::/lower4 simply replacing each non-escaped ":" by "\0". So sequences of non-escaped ":" were counted as layers. For example, the previous lowerdir mount option above would've counted 6 layers instead of 4 and a lowerdir mount option such as: lowerdir="/lower1:/lower2::/lower3::/lower4:::::::::::::::::::::::::::" would be counted as 33 layers. Other than being ugly this didn't matter much because kern_path() would reject the first "\0" layer. However, this overcounting of layers becomes problematic when we base allocations on it where we very much only want to allocate space for 4 layers instead of 33. So the new parsing function rejects non-escaped sequences of colons other than ":" and "::" immediately instead of relying on kern_path(). Link: https://github.com/util-linux/util-linux/issues/2287 Link: https://github.com/util-linux/util-linux/issues/1992 Link: https://bugs.archlinux.org/task/78702 Link: https://lore.kernel.org/linux-unionfs/20230530-klagen-zudem-32c0908c2108@brauner Signed-off-by: Christian Brauner <brauner@kernel.org> Signed-off-by: Amir Goldstein <amir73il@gmail.com> 2023-06-16 21:54:19 +08:00			`copy_up.o export.o params.o`