From: Amir Goldstein <amir73il@gmail.com> mainline inclusion from mainline-v6.7-rc1 commit c63e56a4a6523fcb1358e1878607d77a40b534bb category: feature bugzilla: https://gitee.com/src-openeuler/kernel/issues/IBHLU4 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i... -------------------------------- overlayfs file open (ovl_maybe_lookup_lowerdata) and overlay file llseek take the ovl_inode_lock, without holding upper sb_writers. In case of nested lower overlay that uses same upper fs as this overlay, lockdep will warn about (possibly false positive) circular lock dependency when doing open/llseek of lower ovl file during copy up with our upper sb_writers held, because the locking ordering seems reverse to the locking order in ovl_copy_up_start(): - lower ovl_inode_lock - upper sb_writers Let the copy up "transaction" keeps an elevated mnt write count on upper mnt, but leaves taking upper sb_writers to lower level helpers only when they actually need it. This allows to avoid holding upper sb_writers during lower file open/llseek and prevents the lockdep warning. Minimizing the scope of upper sb_writers during copy up is also needed for fixing another possible deadlocks by a following patch. Signed-off-by: Amir Goldstein <amir73il@gmail.com> Conflicts: fs/overlayfs/copy_up.c [Context differences.] Signed-off-by: Yifan Qiao <qiaoyifan4@huawei.com> --- fs/overlayfs/copy_up.c | 76 ++++++++++++++++++++++++++++++------------ fs/overlayfs/util.c | 8 +++-- 2 files changed, 61 insertions(+), 23 deletions(-) diff --git a/fs/overlayfs/copy_up.c b/fs/overlayfs/copy_up.c index cc5fe472d6e3..8ad22ea5eec0 100644 --- a/fs/overlayfs/copy_up.c +++ b/fs/overlayfs/copy_up.c @@ -252,7 +252,9 @@ static int ovl_copy_up_file(struct ovl_fs *ofs, struct dentry *dentry, return PTR_ERR(old_file); /* Try to use clone_file_range to clone up within the same fs */ + ovl_start_write(dentry); cloned = do_clone_file_range(old_file, 0, new_file, 0, len, 0); + ovl_end_write(dentry); if (cloned == len) goto out_fput; /* Couldn't clone, so now we try to copy the data */ @@ -287,8 +289,12 @@ static int ovl_copy_up_file(struct ovl_fs *ofs, struct dentry *dentry, * it may not recognize all kind of holes and sometimes * only skips partial of hole area. However, it will be * enough for most of the use cases. + * + * We do not hold upper sb_writers throughout the loop to avert + * lockdep warning with llseek of lower file in nested overlay: + * - upper sb_writers + * -- lower ovl_inode_lock (ovl_llseek) */ - if (skip_hole && data_pos < old_pos) { data_pos = vfs_llseek(old_file, old_pos, SEEK_DATA); if (data_pos > old_pos) { @@ -303,9 +309,11 @@ static int ovl_copy_up_file(struct ovl_fs *ofs, struct dentry *dentry, } } + ovl_start_write(dentry); bytes = do_splice_direct(old_file, &old_pos, new_file, &new_pos, this_len, SPLICE_F_MOVE); + ovl_end_write(dentry); if (bytes <= 0) { error = bytes; break; @@ -555,14 +563,16 @@ static int ovl_link_up(struct ovl_copy_up_ctx *c) struct ovl_fs *ofs = OVL_FS(c->dentry->d_sb); struct inode *udir = d_inode(upperdir); + ovl_start_write(c->dentry); + /* Mark parent "impure" because it may now contain non-pure upper */ err = ovl_set_impure(c->parent, upperdir); if (err) - return err; + goto out; err = ovl_set_nlink_lower(c->dentry); if (err) - return err; + goto out; inode_lock_nested(udir, I_MUTEX_PARENT); upper = ovl_lookup_upper(ofs, c->dentry->d_name.name, upperdir, @@ -581,10 +591,12 @@ static int ovl_link_up(struct ovl_copy_up_ctx *c) } inode_unlock(udir); if (err) - return err; + goto out; err = ovl_set_nlink_upper(c->dentry); +out: + ovl_end_write(c->dentry); return err; } @@ -719,21 +731,19 @@ static int ovl_copy_up_workdir(struct ovl_copy_up_ctx *c) .link = c->link }; - /* workdir and destdir could be the same when copying up to indexdir */ - err = -EIO; - if (lock_rename(c->workdir, c->destdir) != NULL) - goto unlock; - err = ovl_prep_cu_creds(c->dentry, &cc); if (err) - goto unlock; + return err; + ovl_start_write(c->dentry); + inode_lock(wdir); temp = ovl_create_temp(ofs, c->workdir, &cattr); + inode_unlock(wdir); + ovl_end_write(c->dentry); ovl_revert_cu_creds(&cc); - err = PTR_ERR(temp); if (IS_ERR(temp)) - goto unlock; + return PTR_ERR(temp); /* * Copy up data first and then xattrs. Writing data after @@ -741,8 +751,21 @@ static int ovl_copy_up_workdir(struct ovl_copy_up_ctx *c) */ path.dentry = temp; err = ovl_copy_up_data(c, &path); - if (err) + /* + * We cannot hold lock_rename() throughout this helper, because or + * lock ordering with sb_writers, which shouldn't be held when calling + * ovl_copy_up_data(), so lock workdir and destdir and make sure that + * temp wasn't moved before copy up completion or cleanup. + * If temp was moved, abort without the cleanup. + */ + ovl_start_write(c->dentry); + if (lock_rename(c->workdir, c->destdir) != NULL || + temp->d_parent != c->workdir) { + err = -EIO; + goto unlock; + } else if (err) { goto cleanup; + } err = ovl_copy_up_metadata(c, temp); if (err) @@ -779,6 +802,7 @@ static int ovl_copy_up_workdir(struct ovl_copy_up_ctx *c) ovl_set_flag(OVL_WHITEOUTS, inode); unlock: unlock_rename(c->workdir, c->destdir); + ovl_end_write(c->dentry); return err; @@ -802,9 +826,10 @@ static int ovl_copy_up_tmpfile(struct ovl_copy_up_ctx *c) if (err) return err; + ovl_start_write(c->dentry); tmpfile = ovl_do_tmpfile(ofs, c->workdir, c->stat.mode); + ovl_end_write(c->dentry); ovl_revert_cu_creds(&cc); - if (IS_ERR(tmpfile)) return PTR_ERR(tmpfile); @@ -815,9 +840,11 @@ static int ovl_copy_up_tmpfile(struct ovl_copy_up_ctx *c) goto out_fput; } + ovl_start_write(c->dentry); + err = ovl_copy_up_metadata(c, temp); if (err) - goto out_fput; + goto out; inode_lock_nested(udir, I_MUTEX_PARENT); @@ -831,7 +858,7 @@ static int ovl_copy_up_tmpfile(struct ovl_copy_up_ctx *c) inode_unlock(udir); if (err) - goto out_fput; + goto out; if (c->metacopy_digest) ovl_set_flag(OVL_HAS_DIGEST, d_inode(c->dentry)); @@ -843,6 +870,8 @@ static int ovl_copy_up_tmpfile(struct ovl_copy_up_ctx *c) ovl_set_upperdata(d_inode(c->dentry)); ovl_inode_update(d_inode(c->dentry), dget(temp)); +out: + ovl_end_write(c->dentry); out_fput: fput(tmpfile); return err; @@ -893,7 +922,9 @@ static int ovl_do_copy_up(struct ovl_copy_up_ctx *c) * Mark parent "impure" because it may now contain non-pure * upper */ + ovl_start_write(c->dentry); err = ovl_set_impure(c->parent, c->destdir); + ovl_end_write(c->dentry); if (err) return err; } @@ -909,6 +940,7 @@ static int ovl_do_copy_up(struct ovl_copy_up_ctx *c) if (c->indexed) ovl_set_flag(OVL_INDEX, d_inode(c->dentry)); + ovl_start_write(c->dentry); if (to_index) { /* Initialize nlink for copy up of disconnected dentry */ err = ovl_set_nlink_upper(c->dentry); @@ -923,6 +955,7 @@ static int ovl_do_copy_up(struct ovl_copy_up_ctx *c) ovl_dentry_set_upper_alias(c->dentry); ovl_dentry_update_reval(c->dentry, ovl_dentry_upper(c->dentry)); } + ovl_end_write(c->dentry); out: if (to_index) @@ -1011,15 +1044,16 @@ static int ovl_copy_up_meta_inode_data(struct ovl_copy_up_ctx *c) * Writing to upper file will clear security.capability xattr. We * don't want that to happen for normal copy-up operation. */ + ovl_start_write(c->dentry); if (capability) { err = ovl_do_setxattr(ofs, upperpath.dentry, XATTR_NAME_CAPS, capability, cap_size, 0); - if (err) - goto out_free; } - - - err = ovl_removexattr(ofs, upperpath.dentry, OVL_XATTR_METACOPY); + if (!err) { + err = ovl_removexattr(ofs, upperpath.dentry, + OVL_XATTR_METACOPY); + } + ovl_end_write(c->dentry); if (err) goto out_free; diff --git a/fs/overlayfs/util.c b/fs/overlayfs/util.c index e9e867119f34..a08901e24096 100644 --- a/fs/overlayfs/util.c +++ b/fs/overlayfs/util.c @@ -673,6 +673,10 @@ bool ovl_already_copied_up(struct dentry *dentry, int flags) return false; } +/* + * The copy up "transaction" keeps an elevated mnt write count on upper mnt, + * but leaves taking freeze protection on upper sb to lower level helpers. + */ int ovl_copy_up_start(struct dentry *dentry, int flags) { struct inode *inode = d_inode(dentry); @@ -685,7 +689,7 @@ int ovl_copy_up_start(struct dentry *dentry, int flags) if (ovl_already_copied_up_locked(dentry, flags)) err = 1; /* Already copied up */ else - err = ovl_want_write(dentry); + err = ovl_get_write_access(dentry); if (err) goto out_unlock; @@ -698,7 +702,7 @@ int ovl_copy_up_start(struct dentry *dentry, int flags) void ovl_copy_up_end(struct dentry *dentry) { - ovl_drop_write(dentry); + ovl_put_write_access(dentry); ovl_inode_unlock(d_inode(dentry)); } -- 2.39.2