Commit 2105c282 authored by David Howells's avatar David Howells
Browse files

afs: Fix race between post-modification dir edit and readdir/d_revalidate 



AFS directories are retained locally as a structured file, with lookup
being effected by a local search of the file contents.  When a modification
(such as mkdir) happens, the dir file content is modified locally rather
than redownloading the directory.

The directory contents are accessed in a number of ways, with a number of
different locks schemes:

 (1) Download of contents - dvnode->validate_lock/write in afs_read_dir().

 (2) Lookup and readdir - dvnode->validate_lock/read in afs_dir_iterate(),
     downgrading from (1) if necessary.

 (3) d_revalidate of child dentry - dvnode->validate_lock/read in
     afs_do_lookup_one() downgrading from (1) if necessary.

 (4) Edit of dir after modification - page locks on individual dir pages.

Unfortunately, because (4) uses different locking scheme to (1) - (3),
nothing protects against the page being scanned whilst the edit is
underway.  Even download is not safe as it doesn't lock the pages - relying
instead on the validate_lock to serialise as a whole (the theory being that
directory contents are treated as a block and always downloaded as a
block).

Fix this by write-locking dvnode->validate_lock around the edits.  Care
must be taken in the rename case as there may be two different dirs - but
they need not be locked at the same time.  In any case, once the lock is
taken, the directory version must be rechecked, and the edit skipped if a
later version has been downloaded by revalidation (there can't have been
any local changes because the VFS holds the inode lock, but there can have
been remote changes).

Fixes: 63a4681f ("afs: Locally edit directory data for mkdir/create/unlink/...")
Signed-off-by: default avatarDavid Howells <dhowells@redhat.com>
parent 3efe55b0

fs/afs/dir.c

+61 −28
Original line number Diff line number Diff line
@@ -1275,6 +1275,7 @@ static int afs_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode) 
	struct afs_fs_cursor fc;

	struct afs_vnode *dvnode = AFS_FS_I(dir);

	struct key *key;

	afs_dataversion_t data_version;

	int ret;



	mode |= S_IFDIR;
@@ -1295,7 +1296,7 @@ static int afs_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode) 


	ret = -ERESTARTSYS;

	if (afs_begin_vnode_operation(&fc, dvnode, key, true)) {

		afs_dataversion_t data_version = dvnode->status.data_version + 1;

		data_version = dvnode->status.data_version + 1;



		while (afs_select_fileserver(&fc)) {

			fc.cb_break = afs_calc_vnode_cb_break(dvnode);
@@ -1316,10 +1317,14 @@ static int afs_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode) 
		goto error_key;

	}



	if (ret == 0 &&

	    test_bit(AFS_VNODE_DIR_VALID, &dvnode->flags))

	if (ret == 0) {

		down_write(&dvnode->validate_lock);

		if (test_bit(AFS_VNODE_DIR_VALID, &dvnode->flags) &&

		    dvnode->status.data_version == data_version)

			afs_edit_dir_add(dvnode, &dentry->d_name, &iget_data.fid,

					 afs_edit_dir_for_create);

		up_write(&dvnode->validate_lock);

	}



	key_put(key);

	kfree(scb);
@@ -1360,6 +1365,7 @@ static int afs_rmdir(struct inode *dir, struct dentry *dentry) 
	struct afs_fs_cursor fc;

	struct afs_vnode *dvnode = AFS_FS_I(dir), *vnode = NULL;

	struct key *key;

	afs_dataversion_t data_version;

	int ret;



	_enter("{%llx:%llu},{%pd}",
@@ -1391,7 +1397,7 @@ static int afs_rmdir(struct inode *dir, struct dentry *dentry) 


	ret = -ERESTARTSYS;

	if (afs_begin_vnode_operation(&fc, dvnode, key, true)) {

		afs_dataversion_t data_version = dvnode->status.data_version + 1;

		data_version = dvnode->status.data_version + 1;



		while (afs_select_fileserver(&fc)) {

			fc.cb_break = afs_calc_vnode_cb_break(dvnode);
@@ -1404,9 +1410,12 @@ static int afs_rmdir(struct inode *dir, struct dentry *dentry) 
		ret = afs_end_vnode_operation(&fc);

		if (ret == 0) {

			afs_dir_remove_subdir(dentry);

			if (test_bit(AFS_VNODE_DIR_VALID, &dvnode->flags))

			down_write(&dvnode->validate_lock);

			if (test_bit(AFS_VNODE_DIR_VALID, &dvnode->flags) &&

			    dvnode->status.data_version == data_version)

				afs_edit_dir_remove(dvnode, &dentry->d_name,

						    afs_edit_dir_for_rmdir);

			up_write(&dvnode->validate_lock);

		}

	}
@@ -1544,10 +1553,15 @@ static int afs_unlink(struct inode *dir, struct dentry *dentry) 
		ret = afs_end_vnode_operation(&fc);

		if (ret == 0 && !(scb[1].have_status || scb[1].have_error))

			ret = afs_dir_remove_link(dvnode, dentry, key);

		if (ret == 0 &&

		    test_bit(AFS_VNODE_DIR_VALID, &dvnode->flags))



		if (ret == 0) {

			down_write(&dvnode->validate_lock);

			if (test_bit(AFS_VNODE_DIR_VALID, &dvnode->flags) &&

			    dvnode->status.data_version == data_version)

				afs_edit_dir_remove(dvnode, &dentry->d_name,

						    afs_edit_dir_for_unlink);

			up_write(&dvnode->validate_lock);

		}

	}



	if (need_rehash && ret < 0 && ret != -ENOENT)
@@ -1573,6 +1587,7 @@ static int afs_create(struct inode *dir, struct dentry *dentry, umode_t mode, 
	struct afs_status_cb *scb;

	struct afs_vnode *dvnode = AFS_FS_I(dir);

	struct key *key;

	afs_dataversion_t data_version;

	int ret;



	mode |= S_IFREG;
@@ -1597,7 +1612,7 @@ static int afs_create(struct inode *dir, struct dentry *dentry, umode_t mode, 


	ret = -ERESTARTSYS;

	if (afs_begin_vnode_operation(&fc, dvnode, key, true)) {

		afs_dataversion_t data_version = dvnode->status.data_version + 1;

		data_version = dvnode->status.data_version + 1;



		while (afs_select_fileserver(&fc)) {

			fc.cb_break = afs_calc_vnode_cb_break(dvnode);
@@ -1618,9 +1633,12 @@ static int afs_create(struct inode *dir, struct dentry *dentry, umode_t mode, 
		goto error_key;

	}



	if (test_bit(AFS_VNODE_DIR_VALID, &dvnode->flags))

	down_write(&dvnode->validate_lock);

	if (test_bit(AFS_VNODE_DIR_VALID, &dvnode->flags) &&

	    dvnode->status.data_version == data_version)

		afs_edit_dir_add(dvnode, &dentry->d_name, &iget_data.fid,

				 afs_edit_dir_for_create);

	up_write(&dvnode->validate_lock);



	kfree(scb);

	key_put(key);
@@ -1648,6 +1666,7 @@ static int afs_link(struct dentry *from, struct inode *dir, 
	struct afs_vnode *dvnode = AFS_FS_I(dir);

	struct afs_vnode *vnode = AFS_FS_I(d_inode(from));

	struct key *key;

	afs_dataversion_t data_version;

	int ret;



	_enter("{%llx:%llu},{%llx:%llu},{%pd}",
@@ -1672,7 +1691,7 @@ static int afs_link(struct dentry *from, struct inode *dir, 


	ret = -ERESTARTSYS;

	if (afs_begin_vnode_operation(&fc, dvnode, key, true)) {

		afs_dataversion_t data_version = dvnode->status.data_version + 1;

		data_version = dvnode->status.data_version + 1;



		if (mutex_lock_interruptible_nested(&vnode->io_lock, 1) < 0) {

			afs_end_vnode_operation(&fc);
@@ -1702,9 +1721,12 @@ static int afs_link(struct dentry *from, struct inode *dir, 
		goto error_key;

	}



	if (test_bit(AFS_VNODE_DIR_VALID, &dvnode->flags))

	down_write(&dvnode->validate_lock);

	if (test_bit(AFS_VNODE_DIR_VALID, &dvnode->flags) &&

	    dvnode->status.data_version == data_version)

		afs_edit_dir_add(dvnode, &dentry->d_name, &vnode->fid,

				 afs_edit_dir_for_link);

	up_write(&dvnode->validate_lock);



	key_put(key);

	kfree(scb);
@@ -1732,6 +1754,7 @@ static int afs_symlink(struct inode *dir, struct dentry *dentry, 
	struct afs_status_cb *scb;

	struct afs_vnode *dvnode = AFS_FS_I(dir);

	struct key *key;

	afs_dataversion_t data_version;

	int ret;



	_enter("{%llx:%llu},{%pd},%s",
@@ -1759,7 +1782,7 @@ static int afs_symlink(struct inode *dir, struct dentry *dentry, 


	ret = -ERESTARTSYS;

	if (afs_begin_vnode_operation(&fc, dvnode, key, true)) {

		afs_dataversion_t data_version = dvnode->status.data_version + 1;

		data_version = dvnode->status.data_version + 1;



		while (afs_select_fileserver(&fc)) {

			fc.cb_break = afs_calc_vnode_cb_break(dvnode);
@@ -1780,9 +1803,12 @@ static int afs_symlink(struct inode *dir, struct dentry *dentry, 
		goto error_key;

	}



	if (test_bit(AFS_VNODE_DIR_VALID, &dvnode->flags))

	down_write(&dvnode->validate_lock);

	if (test_bit(AFS_VNODE_DIR_VALID, &dvnode->flags) &&

	    dvnode->status.data_version == data_version)

		afs_edit_dir_add(dvnode, &dentry->d_name, &iget_data.fid,

				 afs_edit_dir_for_symlink);

	up_write(&dvnode->validate_lock);



	key_put(key);

	kfree(scb);
@@ -1812,6 +1838,8 @@ static int afs_rename(struct inode *old_dir, struct dentry *old_dentry, 
	struct dentry *tmp = NULL, *rehash = NULL;

	struct inode *new_inode;

	struct key *key;

	afs_dataversion_t orig_data_version;

	afs_dataversion_t new_data_version;

	bool new_negative = d_is_negative(new_dentry);

	int ret;
@@ -1890,9 +1918,6 @@ static int afs_rename(struct inode *old_dir, struct dentry *old_dentry, 


	ret = -ERESTARTSYS;

	if (afs_begin_vnode_operation(&fc, orig_dvnode, key, true)) {

		afs_dataversion_t orig_data_version;

		afs_dataversion_t new_data_version;



		orig_data_version = orig_dvnode->status.data_version + 1;



		if (orig_dvnode != new_dvnode) {
@@ -1928,18 +1953,25 @@ static int afs_rename(struct inode *old_dir, struct dentry *old_dentry, 
	if (ret == 0) {

		if (rehash)

			d_rehash(rehash);

		if (test_bit(AFS_VNODE_DIR_VALID, &orig_dvnode->flags))

		down_write(&orig_dvnode->validate_lock);

		if (test_bit(AFS_VNODE_DIR_VALID, &orig_dvnode->flags) &&

		    orig_dvnode->status.data_version == orig_data_version)

			afs_edit_dir_remove(orig_dvnode, &old_dentry->d_name,

					    afs_edit_dir_for_rename_0);

		if (orig_dvnode != new_dvnode) {

			up_write(&orig_dvnode->validate_lock);



		if (!new_negative &&

		    test_bit(AFS_VNODE_DIR_VALID, &new_dvnode->flags))

			down_write(&new_dvnode->validate_lock);

		}

		if (test_bit(AFS_VNODE_DIR_VALID, &new_dvnode->flags) &&

		    orig_dvnode->status.data_version == new_data_version) {

			if (!new_negative)

				afs_edit_dir_remove(new_dvnode, &new_dentry->d_name,

						    afs_edit_dir_for_rename_1);



		if (test_bit(AFS_VNODE_DIR_VALID, &new_dvnode->flags))

			afs_edit_dir_add(new_dvnode, &new_dentry->d_name,

					 &vnode->fid, afs_edit_dir_for_rename_2);

		}



		new_inode = d_inode(new_dentry);

		if (new_inode) {
@@ -1958,6 +1990,7 @@ static int afs_rename(struct inode *old_dir, struct dentry *old_dentry, 
		afs_update_dentry_version(&fc, old_dentry, &scb[1]);

		afs_update_dentry_version(&fc, new_dentry, &scb[1]);

		d_move(old_dentry, new_dentry);

		up_write(&new_dvnode->validate_lock);

		goto error_tmp;

	}

fs/afs/dir_silly.c

+15 −7
Original line number Diff line number Diff line
@@ -21,6 +21,7 @@ static int afs_do_silly_rename(struct afs_vnode *dvnode, struct afs_vnode *vnode 
{

	struct afs_fs_cursor fc;

	struct afs_status_cb *scb;

	afs_dataversion_t dir_data_version;

	int ret = -ERESTARTSYS;



	_enter("%pd,%pd", old, new);
@@ -31,7 +32,7 @@ static int afs_do_silly_rename(struct afs_vnode *dvnode, struct afs_vnode *vnode 


	trace_afs_silly_rename(vnode, false);

	if (afs_begin_vnode_operation(&fc, dvnode, key, true)) {

		afs_dataversion_t dir_data_version = dvnode->status.data_version + 1;

		dir_data_version = dvnode->status.data_version + 1;



		while (afs_select_fileserver(&fc)) {

			fc.cb_break = afs_calc_vnode_cb_break(dvnode);
@@ -54,13 +55,16 @@ static int afs_do_silly_rename(struct afs_vnode *dvnode, struct afs_vnode *vnode 
			dvnode->silly_key = key_get(key);

		}



		if (test_bit(AFS_VNODE_DIR_VALID, &dvnode->flags))

		down_write(&dvnode->validate_lock);

		if (test_bit(AFS_VNODE_DIR_VALID, &dvnode->flags) &&

		    dvnode->status.data_version == dir_data_version) {

			afs_edit_dir_remove(dvnode, &old->d_name,

					    afs_edit_dir_for_silly_0);

		if (test_bit(AFS_VNODE_DIR_VALID, &dvnode->flags))

			afs_edit_dir_add(dvnode, &new->d_name,

					 &vnode->fid, afs_edit_dir_for_silly_1);

		}

		up_write(&dvnode->validate_lock);

	}



	kfree(scb);

	_leave(" = %d", ret);
@@ -181,10 +185,14 @@ static int afs_do_silly_unlink(struct afs_vnode *dvnode, struct afs_vnode *vnode 
				clear_bit(AFS_VNODE_CB_PROMISED, &vnode->flags);

			}

		}

		if (ret == 0 &&

		    test_bit(AFS_VNODE_DIR_VALID, &dvnode->flags))

		if (ret == 0) {

			down_write(&dvnode->validate_lock);

			if (test_bit(AFS_VNODE_DIR_VALID, &dvnode->flags) &&

			    dvnode->status.data_version == dir_data_version)

				afs_edit_dir_remove(dvnode, &dentry->d_name,

						    afs_edit_dir_for_unlink);

			up_write(&dvnode->validate_lock);

		}

	}



	kfree(scb);

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