ovl: persistent overlay inode nlink for indexed inodes (5f8415d6) · Commits · 戴 / test

fs/overlayfs/copy_up.c

+5 −0

Original line number	Diff line number	Diff line
		@@ -323,6 +323,10 @@ static int ovl_link_up(struct dentry parent, struct dentry dentry)
		struct dentry *upperdir = ovl_dentry_upper(parent);
		struct inode *udir = d_inode(upperdir);

		err = ovl_set_nlink_lower(dentry);
		if (err)
		return err;

		inode_lock_nested(udir, I_MUTEX_PARENT);
		upper = lookup_one_len(dentry->d_name.name, upperdir,
		dentry->d_name.len);
		@@ -335,6 +339,7 @@ static int ovl_link_up(struct dentry parent, struct dentry dentry)
		ovl_dentry_set_upper_alias(dentry);
		}
		inode_unlock(udir);
		ovl_set_nlink_upper(dentry);

		return err;
		}

fs/overlayfs/dir.c

+17 −2

Original line number	Diff line number	Diff line
		@@ -591,6 +591,7 @@ static int ovl_link(struct dentry old, struct inode newdir,
		struct dentry *new)
		{
		int err;
		bool locked = false;
		struct inode *inode;

		err = ovl_want_write(old);
		@@ -601,6 +602,10 @@ static int ovl_link(struct dentry old, struct inode newdir,
		if (err)
		goto out_drop_write;

		err = ovl_nlink_start(old, &locked);
		if (err)
		goto out_drop_write;

		inode = d_inode(old);
		ihold(inode);

		@@ -608,6 +613,7 @@ static int ovl_link(struct dentry old, struct inode newdir,
		if (err)
		iput(inode);

		ovl_nlink_end(old, locked);
		out_drop_write:
		ovl_drop_write(old);
		out:
		@@ -743,8 +749,8 @@ out:

		static int ovl_do_remove(struct dentry *dentry, bool is_dir)
		{
		enum ovl_path_type type;
		int err;
		bool locked = false;
		const struct cred *old_cred;

		err = ovl_want_write(dentry);
		@@ -755,7 +761,9 @@ static int ovl_do_remove(struct dentry *dentry, bool is_dir)
		if (err)
		goto out_drop_write;

		type = ovl_path_type(dentry);
		err = ovl_nlink_start(dentry, &locked);
		if (err)
		goto out_drop_write;

		old_cred = ovl_override_creds(dentry->d_sb);
		if (!ovl_lower_positive(dentry))
		@@ -769,6 +777,7 @@ static int ovl_do_remove(struct dentry *dentry, bool is_dir)
		else
		drop_nlink(dentry->d_inode);
		}
		ovl_nlink_end(dentry, locked);
		out_drop_write:
		ovl_drop_write(dentry);
		out:
		@@ -891,6 +900,7 @@ static int ovl_rename(struct inode olddir, struct dentry old,
		unsigned int flags)
		{
		int err;
		bool locked = false;
		struct dentry *old_upperdir;
		struct dentry *new_upperdir;
		struct dentry *olddentry;
		@@ -934,6 +944,10 @@ static int ovl_rename(struct inode olddir, struct dentry old,
		err = ovl_copy_up(new);
		if (err)
		goto out_drop_write;
		} else {
		err = ovl_nlink_start(new, &locked);
		if (err)
		goto out_drop_write;
		}

		old_cred = ovl_override_creds(old->d_sb);
		@@ -1072,6 +1086,7 @@ out_unlock:
		unlock_rename(new_upperdir, old_upperdir);
		out_revert_creds:
		revert_creds(old_cred);
		ovl_nlink_end(new, locked);
		out_drop_write:
		ovl_drop_write(old);
		out:

fs/overlayfs/inode.c

+111 −1

Original line number	Diff line number	Diff line
		@@ -12,6 +12,7 @@
		#include <linux/cred.h>
		#include <linux/xattr.h>
		#include <linux/posix_acl.h>
		#include <linux/ratelimit.h>
		#include "overlayfs.h"

		int ovl_setattr(struct dentry dentry, struct iattr attr)
		@@ -130,6 +131,15 @@ int ovl_getattr(const struct path path, struct kstat stat,
		if (is_dir && OVL_TYPE_MERGE(type))
		stat->nlink = 1;

		/*
		* Return the overlay inode nlinks for indexed upper inodes.
		* Overlay inode nlink counts the union of the upper hardlinks
		* and non-covered lower hardlinks. It does not include the upper
		* index hardlink.
		*/
		if (!is_dir && ovl_test_flag(OVL_INDEX, d_inode(dentry)))
		stat->nlink = dentry->d_inode->i_nlink;

		out:
		revert_creds(old_cred);

		@@ -442,6 +452,103 @@ static void ovl_fill_inode(struct inode *inode, umode_t mode, dev_t rdev)
		}
		}

		/*
		* With inodes index enabled, an overlay inode nlink counts the union of upper
		* hardlinks and non-covered lower hardlinks. During the lifetime of a non-pure
		* upper inode, the following nlink modifying operations can happen:
		*
		* 1. Lower hardlink copy up
		* 2. Upper hardlink created, unlinked or renamed over
		* 3. Lower hardlink whiteout or renamed over
		*
		* For the first, copy up case, the union nlink does not change, whether the
		* operation succeeds or fails, but the upper inode nlink may change.
		* Therefore, before copy up, we store the union nlink value relative to the
		* lower inode nlink in the index inode xattr trusted.overlay.nlink.
		*
		* For the second, upper hardlink case, the union nlink should be incremented
		* or decremented IFF the operation succeeds, aligned with nlink change of the
		* upper inode. Therefore, before link/unlink/rename, we store the union nlink
		* value relative to the upper inode nlink in the index inode.
		*
		* For the last, lower cover up case, we simplify things by preceding the
		* whiteout or cover up with copy up. This makes sure that there is an index
		* upper inode where the nlink xattr can be stored before the copied up upper
		* entry is unlink.
		*/
		#define OVL_NLINK_ADD_UPPER (1 << 0)

		/*
		* On-disk format for indexed nlink:
		*
		* nlink relative to the upper inode - "U[+-]NUM"
		* nlink relative to the lower inode - "L[+-]NUM"
		*/

		static int ovl_set_nlink_common(struct dentry *dentry,
		struct dentry realdentry, const char format)
		{
		struct inode *inode = d_inode(dentry);
		struct inode *realinode = d_inode(realdentry);
		char buf[13];
		int len;

		len = snprintf(buf, sizeof(buf), format,
		(int) (inode->i_nlink - realinode->i_nlink));

		return ovl_do_setxattr(ovl_dentry_upper(dentry),
		OVL_XATTR_NLINK, buf, len, 0);
		}

		int ovl_set_nlink_upper(struct dentry *dentry)
		{
		return ovl_set_nlink_common(dentry, ovl_dentry_upper(dentry), "U%+i");
		}

		int ovl_set_nlink_lower(struct dentry *dentry)
		{
		return ovl_set_nlink_common(dentry, ovl_dentry_lower(dentry), "L%+i");
		}

		static unsigned int ovl_get_nlink(struct dentry *lowerdentry,
		struct dentry *upperdentry,
		unsigned int fallback)
		{
		int nlink_diff;
		int nlink;
		char buf[13];
		int err;

		if (!lowerdentry \|\| !upperdentry \|\| d_inode(lowerdentry)->i_nlink == 1)
		return fallback;

		err = vfs_getxattr(upperdentry, OVL_XATTR_NLINK, &buf, sizeof(buf) - 1);
		if (err < 0)
		goto fail;

		buf[err] = '\0';
		if ((buf[0] != 'L' && buf[0] != 'U') \|\|
		(buf[1] != '+' && buf[1] != '-'))
		goto fail;

		err = kstrtoint(buf + 1, 10, &nlink_diff);
		if (err < 0)
		goto fail;

		nlink = d_inode(buf[0] == 'L' ? lowerdentry : upperdentry)->i_nlink;
		nlink += nlink_diff;

		if (nlink <= 0)
		goto fail;

		return nlink;

		fail:
		pr_warn_ratelimited("overlayfs: failed to get index nlink (%pd2, err=%i)\n",
		upperdentry, err);
		return fallback;
		}

		struct inode ovl_new_inode(struct super_block sb, umode_t mode, dev_t rdev)
		{
		struct inode *inode;
		@@ -495,6 +602,7 @@ struct inode ovl_get_inode(struct dentry dentry, struct dentry *upperdentry)
		if (!S_ISDIR(realinode->i_mode) &&
		(upperdentry \|\| (lowerdentry && ovl_indexdir(dentry->d_sb)))) {
		struct inode *key = d_inode(lowerdentry ?: upperdentry);
		unsigned int nlink;

		inode = iget5_locked(dentry->d_sb, (unsigned long) key,
		ovl_inode_test, ovl_inode_set, key);
		@@ -515,7 +623,9 @@ struct inode ovl_get_inode(struct dentry dentry, struct dentry *upperdentry)
		goto out;
		}

		set_nlink(inode, realinode->i_nlink);
		nlink = ovl_get_nlink(lowerdentry, upperdentry,
		realinode->i_nlink);
		set_nlink(inode, nlink);
		} else {
		inode = new_inode(dentry->d_sb);
		if (!inode)

fs/overlayfs/overlayfs.h

+5 −0

Original line number	Diff line number	Diff line
		@@ -25,6 +25,7 @@ enum ovl_path_type {
		#define OVL_XATTR_REDIRECT OVL_XATTR_PREFIX "redirect"
		#define OVL_XATTR_ORIGIN OVL_XATTR_PREFIX "origin"
		#define OVL_XATTR_IMPURE OVL_XATTR_PREFIX "impure"
		#define OVL_XATTR_NLINK OVL_XATTR_PREFIX "nlink"

		enum ovl_flag {
		OVL_IMPURE,
		@@ -229,6 +230,8 @@ void ovl_set_flag(unsigned long flag, struct inode *inode);
		bool ovl_test_flag(unsigned long flag, struct inode *inode);
		bool ovl_inuse_trylock(struct dentry *dentry);
		void ovl_inuse_unlock(struct dentry *dentry);
		int ovl_nlink_start(struct dentry dentry, bool locked);
		void ovl_nlink_end(struct dentry *dentry, bool locked);

		static inline bool ovl_is_impuredir(struct dentry *dentry)
		{
		@@ -258,6 +261,8 @@ int ovl_indexdir_cleanup(struct dentry dentry, struct vfsmount mnt,
		struct path *lowerstack, unsigned int numlower);

		/* inode.c */
		int ovl_set_nlink_upper(struct dentry *dentry);
		int ovl_set_nlink_lower(struct dentry *dentry);
		int ovl_setattr(struct dentry dentry, struct iattr attr);
		int ovl_getattr(const struct path path, struct kstat stat,
		u32 request_mask, unsigned int flags);

fs/overlayfs/util.c

+66 −0

Original line number	Diff line number	Diff line
		@@ -410,3 +410,69 @@ void ovl_inuse_unlock(struct dentry *dentry)
		spin_unlock(&inode->i_lock);
		}
		}

		/*
		* Operations that change overlay inode and upper inode nlink need to be
		* synchronized with copy up for persistent nlink accounting.
		*/
		int ovl_nlink_start(struct dentry dentry, bool locked)
		{
		struct ovl_inode *oi = OVL_I(d_inode(dentry));
		const struct cred *old_cred;
		int err;

		if (!d_inode(dentry) \|\| d_is_dir(dentry))
		return 0;

		/*
		* With inodes index is enabled, we store the union overlay nlink
		* in an xattr on the index inode. When whiting out lower hardlinks
		* we need to decrement the overlay persistent nlink, but before the
		* first copy up, we have no upper index inode to store the xattr.
		*
		* As a workaround, before whiteout/rename over of a lower hardlink,
		* copy up to create the upper index. Creating the upper index will
		* initialize the overlay nlink, so it could be dropped if unlink
		* or rename succeeds.
		*
		* TODO: implement metadata only index copy up when called with
		* ovl_copy_up_flags(dentry, O_PATH).
		*/
		if (ovl_indexdir(dentry->d_sb) && !ovl_dentry_has_upper_alias(dentry) &&
		d_inode(ovl_dentry_lower(dentry))->i_nlink > 1) {
		err = ovl_copy_up(dentry);
		if (err)
		return err;
		}

		err = mutex_lock_interruptible(&oi->lock);
		if (err)
		return err;

		if (!ovl_test_flag(OVL_INDEX, d_inode(dentry)))
		goto out;

		old_cred = ovl_override_creds(dentry->d_sb);
		/*
		* The overlay inode nlink should be incremented/decremented IFF the
		* upper operation succeeds, along with nlink change of upper inode.
		* Therefore, before link/unlink/rename, we store the union nlink
		* value relative to the upper inode nlink in an upper inode xattr.
		*/
		err = ovl_set_nlink_upper(dentry);
		revert_creds(old_cred);

		out:
		if (err)
		mutex_unlock(&oi->lock);
		else
		*locked = true;

		return err;
		}

		void ovl_nlink_end(struct dentry *dentry, bool locked)
		{
		if (locked)
		mutex_unlock(&OVL_I(d_inode(dentry))->lock);
		}

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