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Registered in England and Wales under Company Registration No. 3798903 Subject: [PATCH 03/25] vfs: Allow fsinfo() to query what's in an fs_context [ver #14] From: David Howells To: viro@zeniv.linux.org.uk Cc: dhowells@redhat.com, raven@themaw.net, mszeredi@redhat.com, linux-api@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org Date: Mon, 24 Jun 2019 15:09:14 +0100 Message-ID: <156138535407.25627.15015993364565647650.stgit@warthog.procyon.org.uk> In-Reply-To: <156138532485.25627.7459410522109581052.stgit@warthog.procyon.org.uk> References: <156138532485.25627.7459410522109581052.stgit@warthog.procyon.org.uk> User-Agent: StGit/unknown-version MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.41]); Mon, 24 Jun 2019 14:09:16 +0000 (UTC) Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org Allow fsinfo() to be used to query the filesystem attached to an fs_context once a superblock has been created or if it comes from fspick(). The caller must specify AT_FSINFO_FROM_FSOPEN in the parameters and must supply the fd from fsopen() as dfd and must set filename to NULL. This is done with something like: fd = fsopen("ext4", 0); ... struct fsinfo_params params = { .at_flags = AT_FSINFO_FROM_FSOPEN; ... }; fsinfo(fd, NULL, ¶ms, ...); Signed-off-by: David Howells --- fs/fsinfo.c | 46 +++++++++++++++++++++++++++++++++++++++++++- fs/statfs.c | 2 +- include/uapi/linux/fcntl.h | 2 ++ 3 files changed, 48 insertions(+), 2 deletions(-) diff --git a/fs/fsinfo.c b/fs/fsinfo.c index 49b46f96dda3..c24701f994d1 100644 --- a/fs/fsinfo.c +++ b/fs/fsinfo.c @@ -8,6 +8,7 @@ #include #include #include +#include #include #include "internal.h" @@ -340,6 +341,42 @@ static int vfs_fsinfo_fd(unsigned int fd, struct fsinfo_kparams *params) return ret; } +/* + * Allow access to an fs_context object as created by fsopen() or fspick(). + */ +static int vfs_fsinfo_fscontext(int fd, struct fsinfo_kparams *params) +{ + struct fs_context *fc; + struct fd f = fdget(fd); + int ret; + + if (!f.file) + return -EBADF; + + ret = -EINVAL; + if (f.file->f_op == &fscontext_fops) + goto out_f; + ret = -EOPNOTSUPP; + if (fc->ops == &legacy_fs_context_ops) + goto out_f; + + ret = mutex_lock_interruptible(&fc->uapi_mutex); + if (ret == 0) { + ret = -EIO; + if (fc->root) { + struct path path = { .dentry = fc->root }; + + ret = vfs_fsinfo(&path, params); + } + + mutex_unlock(&fc->uapi_mutex); + } + +out_f: + fdput(f); + return ret; +} + /* * Return buffer information by requestable attribute. * @@ -445,6 +482,9 @@ SYSCALL_DEFINE5(fsinfo, params.request = user_params.request; params.Nth = user_params.Nth; params.Mth = user_params.Mth; + + if ((params.at_flags & AT_FSINFO_FROM_FSOPEN) && filename) + return -EINVAL; } else { params.request = FSINFO_ATTR_STATFS; } @@ -453,6 +493,8 @@ SYSCALL_DEFINE5(fsinfo, user_buf_size = 0; user_buffer = NULL; } + if ((params.at_flags & AT_FSINFO_FROM_FSOPEN) && filename) + return -EINVAL; /* Allocate an appropriately-sized buffer. We will truncate the * contents when we write the contents back to userspace. @@ -500,7 +542,9 @@ SYSCALL_DEFINE5(fsinfo, if (!params.buffer) goto error_scratch; - if (filename) + if (params.at_flags & AT_FSINFO_FROM_FSOPEN) + ret = vfs_fsinfo_fscontext(dfd, ¶ms); + else if (filename) ret = vfs_fsinfo_path(dfd, filename, ¶ms); else ret = vfs_fsinfo_fd(dfd, ¶ms); diff --git a/fs/statfs.c b/fs/statfs.c index eea7af6f2f22..b9b63d9f4f24 100644 --- a/fs/statfs.c +++ b/fs/statfs.c @@ -86,7 +86,7 @@ int vfs_statfs(const struct path *path, struct kstatfs *buf) int error; error = statfs_by_dentry(path->dentry, buf); - if (!error) + if (!error && path->mnt) buf->f_flags = calculate_f_flags(path->mnt); return error; } diff --git a/include/uapi/linux/fcntl.h b/include/uapi/linux/fcntl.h index 1d338357df8a..6a2402a8fa30 100644 --- a/include/uapi/linux/fcntl.h +++ b/include/uapi/linux/fcntl.h @@ -91,6 +91,8 @@ #define AT_STATX_FORCE_SYNC 0x2000 /* - Force the attributes to be sync'd with the server */ #define AT_STATX_DONT_SYNC 0x4000 /* - Don't sync attributes with the server */ +#define AT_FSINFO_FROM_FSOPEN 0x2000 /* Examine the fs_context attached to dfd by fsopen() */ + #define AT_RECURSIVE 0x8000 /* Apply to the entire subtree */