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SubjectRe: [PATCH AUTOSEL 5.5 487/542] ceph: remove the extra slashes in the server path
On Fri, Feb 14, 2020 at 05:13:21PM +0100, Ilya Dryomov wrote:
>On Fri, Feb 14, 2020 at 4:59 PM Sasha Levin <sashal@kernel.org> wrote:
>>
>> From: Xiubo Li <xiubli@redhat.com>
>>
>> [ Upstream commit 4fbc0c711b2464ee1551850b85002faae0b775d5 ]
>>
>> It's possible to pass the mount helper a server path that has more
>> than one contiguous slash character. For example:
>>
>> $ mount -t ceph 192.168.195.165:40176:/// /mnt/cephfs/
>>
>> In the MDS server side the extra slashes of the server path will be
>> treated as snap dir, and then we can get the following debug logs:
>>
>> ceph: mount opening path //
>> ceph: open_root_inode opening '//'
>> ceph: fill_trace 0000000059b8a3bc is_dentry 0 is_target 1
>> ceph: alloc_inode 00000000dc4ca00b
>> ceph: get_inode created new inode 00000000dc4ca00b 1.ffffffffffffffff ino 1
>> ceph: get_inode on 1=1.ffffffffffffffff got 00000000dc4ca00b
>>
>> And then when creating any new file or directory under the mount
>> point, we can hit the following BUG_ON in ceph_fill_trace():
>>
>> BUG_ON(ceph_snap(dir) != dvino.snap);
>>
>> Have the client ignore the extra slashes in the server path when
>> mounting. This will also canonicalize the path, so that identical mounts
>> can be consilidated.
>>
>> 1) "//mydir1///mydir//"
>> 2) "/mydir1/mydir"
>> 3) "/mydir1/mydir/"
>>
>> Regardless of the internal treatment of these paths, the kernel still
>> stores the original string including the leading '/' for presentation
>> to userland.
>>
>> URL: https://tracker.ceph.com/issues/42771
>> Signed-off-by: Xiubo Li <xiubli@redhat.com>
>> Reviewed-by: Jeff Layton <jlayton@kernel.org>
>> Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
>> Signed-off-by: Sasha Levin <sashal@kernel.org>
>> ---
>> fs/ceph/super.c | 122 ++++++++++++++++++++++++++++++++++++++++--------
>> 1 file changed, 102 insertions(+), 20 deletions(-)
>>
>> diff --git a/fs/ceph/super.c b/fs/ceph/super.c
>> index 430dcf329723a..112927dbd2f20 100644
>> --- a/fs/ceph/super.c
>> +++ b/fs/ceph/super.c
>> @@ -107,7 +107,6 @@ static int ceph_statfs(struct dentry *dentry, struct kstatfs *buf)
>> return 0;
>> }
>>
>> -
>> static int ceph_sync_fs(struct super_block *sb, int wait)
>> {
>> struct ceph_fs_client *fsc = ceph_sb_to_client(sb);
>> @@ -211,7 +210,6 @@ struct ceph_parse_opts_ctx {
>>
>> /*
>> * Parse the source parameter. Distinguish the server list from the path.
>> - * Internally we do not include the leading '/' in the path.
>> *
>> * The source will look like:
>> * <server_spec>[,<server_spec>...]:[<path>]
>> @@ -232,12 +230,15 @@ static int ceph_parse_source(struct fs_parameter *param, struct fs_context *fc)
>>
>> dev_name_end = strchr(dev_name, '/');
>> if (dev_name_end) {
>> - if (strlen(dev_name_end) > 1) {
>> - kfree(fsopt->server_path);
>> - fsopt->server_path = kstrdup(dev_name_end, GFP_KERNEL);
>> - if (!fsopt->server_path)
>> - return -ENOMEM;
>> - }
>> + kfree(fsopt->server_path);
>> +
>> + /*
>> + * The server_path will include the whole chars from userland
>> + * including the leading '/'.
>> + */
>> + fsopt->server_path = kstrdup(dev_name_end, GFP_KERNEL);
>> + if (!fsopt->server_path)
>> + return -ENOMEM;
>> } else {
>> dev_name_end = dev_name + strlen(dev_name);
>> }
>> @@ -461,6 +462,73 @@ static int strcmp_null(const char *s1, const char *s2)
>> return strcmp(s1, s2);
>> }
>>
>> +/**
>> + * path_remove_extra_slash - Remove the extra slashes in the server path
>> + * @server_path: the server path and could be NULL
>> + *
>> + * Return NULL if the path is NULL or only consists of "/", or a string
>> + * without any extra slashes including the leading slash(es) and the
>> + * slash(es) at the end of the server path, such as:
>> + * "//dir1////dir2///" --> "dir1/dir2"
>> + */
>> +static char *path_remove_extra_slash(const char *server_path)
>> +{
>> + const char *path = server_path;
>> + const char *cur, *end;
>> + char *buf, *p;
>> + int len;
>> +
>> + /* if the server path is omitted */
>> + if (!path)
>> + return NULL;
>> +
>> + /* remove all the leading slashes */
>> + while (*path == '/')
>> + path++;
>> +
>> + /* if the server path only consists of slashes */
>> + if (*path == '\0')
>> + return NULL;
>> +
>> + len = strlen(path);
>> +
>> + buf = kmalloc(len + 1, GFP_KERNEL);
>> + if (!buf)
>> + return ERR_PTR(-ENOMEM);
>> +
>> + end = path + len;
>> + p = buf;
>> + do {
>> + cur = strchr(path, '/');
>> + if (!cur)
>> + cur = end;
>> +
>> + len = cur - path;
>> +
>> + /* including one '/' */
>> + if (cur != end)
>> + len += 1;
>> +
>> + memcpy(p, path, len);
>> + p += len;
>> +
>> + while (cur <= end && *cur == '/')
>> + cur++;
>> + path = cur;
>> + } while (path < end);
>> +
>> + *p = '\0';
>> +
>> + /*
>> + * remove the last slash if there has and just to make sure that
>> + * we will get something like "dir1/dir2"
>> + */
>> + if (*(--p) == '/')
>> + *p = '\0';
>> +
>> + return buf;
>> +}
>> +
>> static int compare_mount_options(struct ceph_mount_options *new_fsopt,
>> struct ceph_options *new_opt,
>> struct ceph_fs_client *fsc)
>> @@ -468,6 +536,7 @@ static int compare_mount_options(struct ceph_mount_options *new_fsopt,
>> struct ceph_mount_options *fsopt1 = new_fsopt;
>> struct ceph_mount_options *fsopt2 = fsc->mount_options;
>> int ofs = offsetof(struct ceph_mount_options, snapdir_name);
>> + char *p1, *p2;
>> int ret;
>>
>> ret = memcmp(fsopt1, fsopt2, ofs);
>> @@ -480,9 +549,21 @@ static int compare_mount_options(struct ceph_mount_options *new_fsopt,
>> ret = strcmp_null(fsopt1->mds_namespace, fsopt2->mds_namespace);
>> if (ret)
>> return ret;
>> - ret = strcmp_null(fsopt1->server_path, fsopt2->server_path);
>> +
>> + p1 = path_remove_extra_slash(fsopt1->server_path);
>> + if (IS_ERR(p1))
>> + return PTR_ERR(p1);
>> + p2 = path_remove_extra_slash(fsopt2->server_path);
>> + if (IS_ERR(p2)) {
>> + kfree(p1);
>> + return PTR_ERR(p2);
>> + }
>> + ret = strcmp_null(p1, p2);
>> + kfree(p1);
>> + kfree(p2);
>> if (ret)
>> return ret;
>> +
>> ret = strcmp_null(fsopt1->fscache_uniq, fsopt2->fscache_uniq);
>> if (ret)
>> return ret;
>> @@ -788,7 +869,6 @@ static void destroy_caches(void)
>> ceph_fscache_unregister();
>> }
>>
>> -
>> /*
>> * ceph_umount_begin - initiate forced umount. Tear down down the
>> * mount, skipping steps that may hang while waiting for server(s).
>> @@ -868,9 +948,6 @@ static struct dentry *open_root_dentry(struct ceph_fs_client *fsc,
>> return root;
>> }
>>
>> -
>> -
>> -
>> /*
>> * mount: join the ceph cluster, and open root directory.
>> */
>> @@ -885,7 +962,7 @@ static struct dentry *ceph_real_mount(struct ceph_fs_client *fsc,
>> mutex_lock(&fsc->client->mount_mutex);
>>
>> if (!fsc->sb->s_root) {
>> - const char *path;
>> + const char *path, *p;
>> err = __ceph_open_session(fsc->client, started);
>> if (err < 0)
>> goto out;
>> @@ -897,17 +974,22 @@ static struct dentry *ceph_real_mount(struct ceph_fs_client *fsc,
>> goto out;
>> }
>>
>> - if (!fsc->mount_options->server_path) {
>> - path = "";
>> - dout("mount opening path \\t\n");
>> - } else {
>> - path = fsc->mount_options->server_path + 1;
>> - dout("mount opening path %s\n", path);
>> + p = path_remove_extra_slash(fsc->mount_options->server_path);
>> + if (IS_ERR(p)) {
>> + err = PTR_ERR(p);
>> + goto out;
>> }
>> + /* if the server path is omitted or just consists of '/' */
>> + if (!p)
>> + path = "";
>> + else
>> + path = p;
>> + dout("mount opening path '%s'\n", path);
>>
>> ceph_fs_debugfs_init(fsc);
>>
>> root = open_root_dentry(fsc, path, started);
>> + kfree(p);
>> if (IS_ERR(root)) {
>> err = PTR_ERR(root);
>> goto out;
>
>Hi Sasha,
>
>This commit is buggy, the fix should land in 5.6-rc2. Please drop it
>for now -- it would need to be taken together with "ceph: canonicalize
>server path in place" or not backported at all.

I'll try and queue up the fix when it's upstream. This series will
probably be queued closer to -rc3 anyways.

--
Thanks,
Sasha

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