Commit a0c5ad30 authored by Amir Goldstein's avatar Amir Goldstein Committed by Miklos Szeredi
Browse files

ovl: relax same fs constraint for constant st_ino 



For the case of all layers not on the same fs, return the copy up origin
inode st_dev/st_ino for non-dir from stat(2).

This guaranties constant st_dev/st_ino for non-dir across copy up.
Like the same fs case, st_ino of non-dir is also persistent.

If the st_dev/st_ino for copied up object would have been the same as
that of the real underlying lower file, running diff on underlying lower
file and overlay copied up file would result in diff reporting that the
two files are equal when in fact, they may have different content.

Therefore, unlike the same fs case, st_dev is not persistent because it
uses the unique anonymous bdev allocated for the lower layer.

Signed-off-by: default avatarAmir Goldstein <amir73il@gmail.com>
Signed-off-by: default avatarMiklos Szeredi <mszeredi@redhat.com>
parent ba1e563c

fs/overlayfs/inode.c

+29 −20
Original line number Original line Diff line number Diff line
@@ -74,6 +74,7 @@ int ovl_getattr(const struct path *path, struct kstat *stat, 
	struct path realpath;

	struct path realpath;

	const struct cred *old_cred;

	const struct cred *old_cred;

	bool is_dir = S_ISDIR(dentry->d_inode->i_mode);

	bool is_dir = S_ISDIR(dentry->d_inode->i_mode);

	bool samefs = ovl_same_sb(dentry->d_sb);

	int err;

	int err;





	type = ovl_path_real(dentry, &realpath);

	type = ovl_path_real(dentry, &realpath);
@@ -83,16 +84,13 @@ int ovl_getattr(const struct path *path, struct kstat *stat, 
		goto out;

		goto out;





	/*

	/*

	 * When all layers are on the same fs, all real inode number are

	 * For non-dir or same fs, we use st_ino of the copy up origin, if we

	 * unique, so we use the overlay st_dev, which is friendly to du -x.

	 * know it. This guaranties constant st_dev/st_ino across copy up.

	 *

	 * We also use st_ino of the copy up origin, if we know it.

	 * This guaranties constant st_dev/st_ino across copy up.

	 *

	 *

	 * If filesystem supports NFS export ops, this also guaranties

	 * If filesystem supports NFS export ops, this also guaranties

	 * persistent st_ino across mount cycle.

	 * persistent st_ino across mount cycle.

	 */

	 */

	if (ovl_same_sb(dentry->d_sb)) {

	if (!is_dir || samefs) {

		if (OVL_TYPE_ORIGIN(type)) {

		if (OVL_TYPE_ORIGIN(type)) {

			struct kstat lowerstat;

			struct kstat lowerstat;

			u32 lowermask = STATX_INO | (!is_dir ? STATX_NLINK : 0);

			u32 lowermask = STATX_INO | (!is_dir ? STATX_NLINK : 0);
@@ -103,7 +101,6 @@ int ovl_getattr(const struct path *path, struct kstat *stat, 
			if (err)

			if (err)

				goto out;

				goto out;





			WARN_ON_ONCE(stat->dev != lowerstat.dev);

			/*

			/*

			 * Lower hardlinks may be broken on copy up to different

			 * Lower hardlinks may be broken on copy up to different

			 * upper files, so we cannot use the lower origin st_ino

			 * upper files, so we cannot use the lower origin st_ino
@@ -115,27 +112,39 @@ int ovl_getattr(const struct path *path, struct kstat *stat, 
			if (is_dir || lowerstat.nlink == 1 ||

			if (is_dir || lowerstat.nlink == 1 ||

			    ovl_test_flag(OVL_INDEX, d_inode(dentry)))

			    ovl_test_flag(OVL_INDEX, d_inode(dentry)))

				stat->ino = lowerstat.ino;

				stat->ino = lowerstat.ino;



			if (samefs)

				WARN_ON_ONCE(stat->dev != lowerstat.dev);

			else

				stat->dev = ovl_get_pseudo_dev(dentry);

		}

		}

		if (samefs) {

			/*

			 * When all layers are on the same fs, all real inode

			 * number are unique, so we use the overlay st_dev,

			 * which is friendly to du -x.

			 */

			stat->dev = dentry->d_sb->s_dev;

			stat->dev = dentry->d_sb->s_dev;

	} else if (is_dir) {

		} else if (!OVL_TYPE_UPPER(type)) {

			/*

			 * For non-samefs setup, to make sure that st_dev/st_ino

			 * pair is unique across the system, we use a unique

			 * anonymous st_dev for lower layer inode.

			 */

			stat->dev = ovl_get_pseudo_dev(dentry);

		}

	} else {

		/*

		/*

		 * If not all layers are on the same fs the pair {real st_ino;

		 * overlay st_dev} is not unique, so use the non persistent

		 * overlay st_ino.

		 *

		 * Always use the overlay st_dev for directories, so 'find

		 * Always use the overlay st_dev for directories, so 'find

		 * -xdev' will scan the entire overlay mount and won't cross the

		 * -xdev' will scan the entire overlay mount and won't cross the

		 * overlay mount boundaries.

		 * overlay mount boundaries.

		 *

		 * If not all layers are on the same fs the pair {real st_ino;

		 * overlay st_dev} is not unique, so use the non persistent

		 * overlay st_ino for directories.

		 */

		 */

		stat->dev = dentry->d_sb->s_dev;

		stat->dev = dentry->d_sb->s_dev;

		stat->ino = dentry->d_inode->i_ino;

		stat->ino = dentry->d_inode->i_ino;

	} else if (!OVL_TYPE_UPPER(type)) {

		/*

		 * For non-samefs setup, to make sure that st_dev/st_ino pair

		 * is unique across the system, we use a unique anonymous

		 * st_dev for lower layer inode.

		 */

		stat->dev = ovl_get_pseudo_dev(dentry);

	}

	}





	/*

	/*

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