From mboxrd@z Thu Jan 1 00:00:00 1970 From: Glauber Costa Subject: [PATCH 4/4] parse options in the vfs level Date: Fri, 29 Jul 2011 17:44:19 +0400 Message-ID: <1311947059-17209-5-git-send-email-glommer@parallels.com> References: <1311947059-17209-1-git-send-email-glommer@parallels.com> Cc: linux-fsdevel@vger.kernel.org, containers@lists.linux-foundation.org, Pavel Emelyanov , Al Viro , Hugh Dickins , Nick Piggin , Andrea Arcangeli , Rik van Riel , Dave Hansen , James Bottomley , David Chinner , Glauber Costa To: linux-kernel@vger.kernel.org Return-path: In-Reply-To: <1311947059-17209-1-git-send-email-glommer@parallels.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org This patch introduces a simple generic vfs option parser. Right now, the only option we have is to limit the size of the dcache. So any user that wants to have a dcache entries limit, can specify: mount -o whatever_options,vfs_dcache_size=XXX It is supposed to work well with remounts, allowing it to change multiple over the course of the filesystem's lifecycle. I find mount a natural interface for handling filesystem options, so that's what I've choosen. Feel free to yell at it at will if you disagree. Signed-off-by: Glauber Costa CC: Dave Chinner --- fs/namespace.c | 89 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 files changed, 89 insertions(+), 0 deletions(-) diff --git a/fs/namespace.c b/fs/namespace.c index 22bfe82..11ce45d 100644 --- a/fs/namespace.c +++ b/fs/namespace.c @@ -31,6 +31,7 @@ #include #include #include +#include #include #include #include "pnode.h" @@ -2271,6 +2272,82 @@ int copy_mount_string(const void __user *data, char **where) return 0; } +static const match_table_t tokens = { + {1, "vfs_dcache_size=%u"}, +}; + +struct vfs_options { + unsigned long vfs_dcache_size; +}; + +/** + * Generic option parsing for the VFS. + * + * Since most of the filesystems already do their own option parsing, and with + * very few code shared between them, this function strips out any options that + * we succeed in parsing ourselves. Passing them forward would just give the + * underlying fs an option it does not expect, leading it to fail. + * + * We don't yet have a pointer to the super block as well, since this is + * pre-mount. We accumulate in struct vfs_options whatever data we collected, + * and act on it later. + */ +static int vfs_parse_options(char *options, struct vfs_options *ops) +{ + substring_t args[MAX_OPT_ARGS]; + unsigned int option; + char *p; + char *opt; + char *start = NULL; + int ret; + + if (!options) + return 0; + + opt = kstrdup(options, GFP_KERNEL); + if (!opt) + return 1; + + ret = 1; + + start = opt; + while ((p = strsep(&opt, ",")) != NULL) { + int token; + if (!*p) + continue; + + /* + * Initialize args struct so we know whether arg was + * found; some options take optional arguments. + */ + args[0].to = args[0].from = 0; + token = match_token(p, tokens, args); + switch (token) { + case 1: + if (!args[0].from) + break; + + if (match_int(&args[0], &option)) + break; + else + ops->vfs_dcache_size = option; + + ret = 0; + if (!opt) /* it is the last option listed */ + *(options + (p - start)) = '\0'; + else + strcpy(options + (p - start), opt); + break; + default: + ret = 0; + break; + } + } + + kfree(start); + return ret; +} + /* * Flags is a 32-bit value that allows up to 31 non-fs dependent flags to * be given to the mount() call (ie: read-only, no-dev, no-suid etc). @@ -2291,6 +2368,7 @@ long do_mount(char *dev_name, char *dir_name, char *type_page, struct path path; int retval = 0; int mnt_flags = 0; + struct vfs_options vfs_options; /* Discard magic */ if ((flags & MS_MGC_MSK) == MS_MGC_VAL) @@ -2318,6 +2396,12 @@ long do_mount(char *dev_name, char *dir_name, char *type_page, if (!(flags & MS_NOATIME)) mnt_flags |= MNT_RELATIME; + + vfs_options.vfs_dcache_size = INT_MAX; + retval = vfs_parse_options(data_page, &vfs_options); + if (retval) + goto dput_out; + /* Separate the per-mountpoint flags */ if (flags & MS_NOSUID) mnt_flags |= MNT_NOSUID; @@ -2350,6 +2434,11 @@ long do_mount(char *dev_name, char *dir_name, char *type_page, else retval = do_new_mount(&path, type_page, flags, mnt_flags, dev_name, data_page); + + if (!retval) + vfs_set_dcache_size(path.mnt->mnt_sb, + vfs_options.vfs_dcache_size); + dput_out: path_put(&path); return retval; -- 1.7.6