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authorDavid Howells <dhowells@redhat.com>2018-11-01 23:36:09 +0000
committerAl Viro <viro@zeniv.linux.org.uk>2019-03-20 18:49:06 -0400
commitecdab150fddb42fe6a739335257949220033b782 (patch)
treedf036d4821bb48fe0f369cc91087fcf442d72339 /fs/fs_context.c
parent007ec26cdc9fefacbed85b592afc69413194499c (diff)
downloadlwn-ecdab150fddb42fe6a739335257949220033b782.tar.gz
lwn-ecdab150fddb42fe6a739335257949220033b782.zip
vfs: syscall: Add fsconfig() for configuring and managing a context
Add a syscall for configuring a filesystem creation context and triggering actions upon it, to be used in conjunction with fsopen, fspick and fsmount. long fsconfig(int fs_fd, unsigned int cmd, const char *key, const void *value, int aux); Where fs_fd indicates the context, cmd indicates the action to take, key indicates the parameter name for parameter-setting actions and, if needed, value points to a buffer containing the value and aux can give more information for the value. The following command IDs are proposed: (*) FSCONFIG_SET_FLAG: No value is specified. The parameter must be boolean in nature. The key may be prefixed with "no" to invert the setting. value must be NULL and aux must be 0. (*) FSCONFIG_SET_STRING: A string value is specified. The parameter can be expecting boolean, integer, string or take a path. A conversion to an appropriate type will be attempted (which may include looking up as a path). value points to a NUL-terminated string and aux must be 0. (*) FSCONFIG_SET_BINARY: A binary blob is specified. value points to the blob and aux indicates its size. The parameter must be expecting a blob. (*) FSCONFIG_SET_PATH: A non-empty path is specified. The parameter must be expecting a path object. value points to a NUL-terminated string that is the path and aux is a file descriptor at which to start a relative lookup or AT_FDCWD. (*) FSCONFIG_SET_PATH_EMPTY: As fsconfig_set_path, but with AT_EMPTY_PATH implied. (*) FSCONFIG_SET_FD: An open file descriptor is specified. value must be NULL and aux indicates the file descriptor. (*) FSCONFIG_CMD_CREATE: Trigger superblock creation. (*) FSCONFIG_CMD_RECONFIGURE: Trigger superblock reconfiguration. For the "set" command IDs, the idea is that the file_system_type will point to a list of parameters and the types of value that those parameters expect to take. The core code can then do the parse and argument conversion and then give the LSM and FS a cooked option or array of options to use. Source specification is also done the same way same way, using special keys "source", "source1", "source2", etc.. [!] Note that, for the moment, the key and value are just glued back together and handed to the filesystem. Every filesystem that uses options uses match_token() and co. to do this, and this will need to be changed - but not all at once. Example usage: fd = fsopen("ext4", FSOPEN_CLOEXEC); fsconfig(fd, fsconfig_set_path, "source", "/dev/sda1", AT_FDCWD); fsconfig(fd, fsconfig_set_path_empty, "journal_path", "", journal_fd); fsconfig(fd, fsconfig_set_fd, "journal_fd", "", journal_fd); fsconfig(fd, fsconfig_set_flag, "user_xattr", NULL, 0); fsconfig(fd, fsconfig_set_flag, "noacl", NULL, 0); fsconfig(fd, fsconfig_set_string, "sb", "1", 0); fsconfig(fd, fsconfig_set_string, "errors", "continue", 0); fsconfig(fd, fsconfig_set_string, "data", "journal", 0); fsconfig(fd, fsconfig_set_string, "context", "unconfined_u:...", 0); fsconfig(fd, fsconfig_cmd_create, NULL, NULL, 0); mfd = fsmount(fd, FSMOUNT_CLOEXEC, MS_NOEXEC); or: fd = fsopen("ext4", FSOPEN_CLOEXEC); fsconfig(fd, fsconfig_set_string, "source", "/dev/sda1", 0); fsconfig(fd, fsconfig_cmd_create, NULL, NULL, 0); mfd = fsmount(fd, FSMOUNT_CLOEXEC, MS_NOEXEC); or: fd = fsopen("afs", FSOPEN_CLOEXEC); fsconfig(fd, fsconfig_set_string, "source", "#grand.central.org:root.cell", 0); fsconfig(fd, fsconfig_cmd_create, NULL, NULL, 0); mfd = fsmount(fd, FSMOUNT_CLOEXEC, MS_NOEXEC); or: fd = fsopen("jffs2", FSOPEN_CLOEXEC); fsconfig(fd, fsconfig_set_string, "source", "mtd0", 0); fsconfig(fd, fsconfig_cmd_create, NULL, NULL, 0); mfd = fsmount(fd, FSMOUNT_CLOEXEC, MS_NOEXEC); Signed-off-by: David Howells <dhowells@redhat.com> cc: linux-api@vger.kernel.org Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Diffstat (limited to 'fs/fs_context.c')
-rw-r--r--fs/fs_context.c51
1 files changed, 51 insertions, 0 deletions
diff --git a/fs/fs_context.c b/fs/fs_context.c
index dcf3786f90f9..a47ccd5a4a78 100644
--- a/fs/fs_context.c
+++ b/fs/fs_context.c
@@ -721,3 +721,54 @@ int parse_monolithic_mount_data(struct fs_context *fc, void *data)
return monolithic_mount_data(fc, data);
}
+
+/*
+ * Clean up a context after performing an action on it and put it into a state
+ * from where it can be used to reconfigure a superblock.
+ *
+ * Note that here we do only the parts that can't fail; the rest is in
+ * finish_clean_context() below and in between those fs_context is marked
+ * FS_CONTEXT_AWAITING_RECONF. The reason for splitup is that after
+ * successful mount or remount we need to report success to userland.
+ * Trying to do full reinit (for the sake of possible subsequent remount)
+ * and failing to allocate memory would've put us into a nasty situation.
+ * So here we only discard the old state and reinitialization is left
+ * until we actually try to reconfigure.
+ */
+void vfs_clean_context(struct fs_context *fc)
+{
+ if (fc->need_free && fc->ops && fc->ops->free)
+ fc->ops->free(fc);
+ fc->need_free = false;
+ fc->fs_private = NULL;
+ fc->s_fs_info = NULL;
+ fc->sb_flags = 0;
+ security_free_mnt_opts(&fc->security);
+ kfree(fc->subtype);
+ fc->subtype = NULL;
+ kfree(fc->source);
+ fc->source = NULL;
+
+ fc->purpose = FS_CONTEXT_FOR_RECONFIGURE;
+ fc->phase = FS_CONTEXT_AWAITING_RECONF;
+}
+
+int finish_clean_context(struct fs_context *fc)
+{
+ int error;
+
+ if (fc->phase != FS_CONTEXT_AWAITING_RECONF)
+ return 0;
+
+ if (fc->fs_type->init_fs_context)
+ error = fc->fs_type->init_fs_context(fc);
+ else
+ error = legacy_init_fs_context(fc);
+ if (unlikely(error)) {
+ fc->phase = FS_CONTEXT_FAILED;
+ return error;
+ }
+ fc->need_free = true;
+ fc->phase = FS_CONTEXT_RECONF_PARAMS;
+ return 0;
+}