From f168f1098dd9038daaf9f7be5f81cdea4985886a Mon Sep 17 00:00:00 2001 From: Amir Goldstein Date: Fri, 19 Jan 2018 11:26:53 +0200 Subject: ovl: add support for "nfs_export" configuration Introduce the "nfs_export" config, module and mount options. The NFS export feature depends on the "index" feature and enables two implicit overlayfs features: "index_all" and "verify_lower". The "index_all" feature creates an index on copy up of every file and directory. The "verify_lower" feature uses the full index to detect overlay filesystems inconsistencies on lookup, like redirect from multiple upper dirs to the same lower dir. NFS export can be enabled for non-upper mount with no index. However, because lower layer redirects cannot be verified with the index, enabling NFS export support on an overlay with no upper layer requires turning off redirect follow (e.g. "redirect_dir=nofollow"). The full index may incur some overhead on mount time, especially when verifying that lower directory file handles are not stale. NFS export support, full index and consistency verification will be implemented by following patches. Signed-off-by: Amir Goldstein Signed-off-by: Miklos Szeredi --- fs/overlayfs/super.c | 49 ++++++++++++++++++++++++++++++++++++++++++++----- 1 file changed, 44 insertions(+), 5 deletions(-) (limited to 'fs/overlayfs/super.c') diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c index 4ebbb368fce8..1d538be87fa0 100644 --- a/fs/overlayfs/super.c +++ b/fs/overlayfs/super.c @@ -45,6 +45,11 @@ module_param_named(index, ovl_index_def, bool, 0644); MODULE_PARM_DESC(ovl_index_def, "Default to on or off for the inodes index feature"); +static bool ovl_nfs_export_def = IS_ENABLED(CONFIG_OVERLAY_FS_NFS_EXPORT); +module_param_named(nfs_export, ovl_nfs_export_def, bool, 0644); +MODULE_PARM_DESC(ovl_nfs_export_def, + "Default to on or off for the NFS export feature"); + static void ovl_entry_stack_free(struct ovl_entry *oe) { unsigned int i; @@ -342,6 +347,9 @@ static int ovl_show_options(struct seq_file *m, struct dentry *dentry) seq_printf(m, ",redirect_dir=%s", ofs->config.redirect_mode); if (ofs->config.index != ovl_index_def) seq_printf(m, ",index=%s", ofs->config.index ? "on" : "off"); + if (ofs->config.nfs_export != ovl_nfs_export_def) + seq_printf(m, ",nfs_export=%s", ofs->config.nfs_export ? + "on" : "off"); return 0; } @@ -374,6 +382,8 @@ enum { OPT_REDIRECT_DIR, OPT_INDEX_ON, OPT_INDEX_OFF, + OPT_NFS_EXPORT_ON, + OPT_NFS_EXPORT_OFF, OPT_ERR, }; @@ -385,6 +395,8 @@ static const match_table_t ovl_tokens = { {OPT_REDIRECT_DIR, "redirect_dir=%s"}, {OPT_INDEX_ON, "index=on"}, {OPT_INDEX_OFF, "index=off"}, + {OPT_NFS_EXPORT_ON, "nfs_export=on"}, + {OPT_NFS_EXPORT_OFF, "nfs_export=off"}, {OPT_ERR, NULL} }; @@ -491,6 +503,14 @@ static int ovl_parse_opt(char *opt, struct ovl_config *config) config->index = false; break; + case OPT_NFS_EXPORT_ON: + config->nfs_export = true; + break; + + case OPT_NFS_EXPORT_OFF: + config->nfs_export = false; + break; + default: pr_err("overlayfs: unrecognized mount option \"%s\" or missing value\n", p); return -EINVAL; @@ -696,13 +716,16 @@ static int ovl_lower_dir(const char *name, struct path *path, *remote = true; /* - * The inodes index feature needs to encode and decode file - * handles, so it requires that all layers support them. + * The inodes index feature and NFS export need to encode and decode + * file handles, so they require that all layers support them. */ - if (ofs->config.index && ofs->config.upperdir && + if ((ofs->config.nfs_export || + (ofs->config.index && ofs->config.upperdir)) && !ovl_can_decode_fh(path->dentry->d_sb)) { ofs->config.index = false; - pr_warn("overlayfs: fs on '%s' does not support file handles, falling back to index=off.\n", name); + ofs->config.nfs_export = false; + pr_warn("overlayfs: fs on '%s' does not support file handles, falling back to index=off,nfs_export=off.\n", + name); } return 0; @@ -983,6 +1006,12 @@ static int ovl_make_workdir(struct ovl_fs *ofs, struct path *workpath) pr_warn("overlayfs: upper fs does not support file handles, falling back to index=off.\n"); } + /* NFS export of r/w mount depends on index */ + if (ofs->config.nfs_export && !ofs->config.index) { + pr_warn("overlayfs: NFS export requires \"index=on\", falling back to nfs_export=off.\n"); + ofs->config.nfs_export = false; + } + out: mnt_drop_write(mnt); return err; @@ -1141,6 +1170,10 @@ static struct ovl_entry *ovl_get_lowerstack(struct super_block *sb, } else if (!ofs->config.upperdir && stacklen == 1) { pr_err("overlayfs: at least 2 lowerdir are needed while upperdir nonexistent\n"); goto out_err; + } else if (!ofs->config.upperdir && ofs->config.nfs_export && + ofs->config.redirect_follow) { + pr_warn("overlayfs: NFS export requires \"redirect_dir=nofollow\" on non-upper mount, falling back to nfs_export=off.\n"); + ofs->config.nfs_export = false; } err = -ENOMEM; @@ -1217,6 +1250,7 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent) goto out_err; ofs->config.index = ovl_index_def; + ofs->config.nfs_export = ovl_nfs_export_def; err = ovl_parse_opt((char *) data, &ofs->config); if (err) goto out_err; @@ -1277,8 +1311,13 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent) } /* Show index=off in /proc/mounts for forced r/o mount */ - if (!ofs->indexdir) + if (!ofs->indexdir) { ofs->config.index = false; + if (ofs->upper_mnt && ofs->config.nfs_export) { + pr_warn("overlayfs: NFS export requires an index dir, falling back to nfs_export=off.\n"); + ofs->config.nfs_export = false; + } + } /* Never override disk quota limits or use reserved space */ cap_lower(cred->cap_effective, CAP_SYS_RESOURCE); -- cgit v1.2.3