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cifs: Add support for failover in cifs_mount()
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This patch adds support for failover when failing to connect in
cifs_mount().

Signed-off-by: Paulo Alcantara <palcantara@suse.de>
Reviewed-by: Aurelien Aptel <aaptel@suse.com>
Signed-off-by: Steve French <stfrench@microsoft.com>
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Paulo Alcantara authored and Steve French committed Dec 28, 2018
1 parent 5a65050 commit 4a367dc
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Showing 3 changed files with 236 additions and 15 deletions.
20 changes: 15 additions & 5 deletions fs/cifs/cifs_dfs_ref.c
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Original file line number Diff line number Diff line change
Expand Up @@ -255,20 +255,30 @@ static struct vfsmount *cifs_dfs_do_refmount(struct dentry *mntpt,
{
struct vfsmount *mnt;
char *mountdata;
char *devname = NULL;
char *devname;

/*
* Always pass down the DFS full path to smb3_do_mount() so we
* can use it later for failover.
*/
devname = kstrndup(fullpath, strlen(fullpath), GFP_KERNEL);
if (!devname)
return ERR_PTR(-ENOMEM);

convert_delimiter(devname, '/');

/* strip first '\' from fullpath */
mountdata = cifs_compose_mount_options(cifs_sb->mountdata,
fullpath + 1, ref, &devname);

if (IS_ERR(mountdata))
fullpath + 1, ref, NULL);
if (IS_ERR(mountdata)) {
kfree(devname);
return (struct vfsmount *)mountdata;
}

mnt = vfs_submount(mntpt, &cifs_fs_type, devname, mountdata);
kfree(mountdata);
kfree(devname);
return mnt;

}

static void dump_referral(const struct dfs_info3_param *ref)
Expand Down
228 changes: 218 additions & 10 deletions fs/cifs/connect.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -3891,10 +3891,11 @@ static int mount_setup_tlink(struct cifs_sb_info *cifs_sb, struct cifs_ses *ses,
*/
static char *
build_unc_path_to_root(const struct smb_vol *vol,
const struct cifs_sb_info *cifs_sb)
const struct cifs_sb_info *cifs_sb, bool useppath)
{
char *full_path, *pos;
unsigned int pplen = vol->prepath ? strlen(vol->prepath) + 1 : 0;
unsigned int pplen = useppath && vol->prepath ?
strlen(vol->prepath) + 1 : 0;
unsigned int unc_len = strnlen(vol->UNC, MAX_TREE_SIZE + 1);

full_path = kmalloc(unc_len + pplen + 1, GFP_KERNEL);
Expand Down Expand Up @@ -3939,7 +3940,7 @@ expand_dfs_referral(const unsigned int xid, struct cifs_ses *ses,
if (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_NO_DFS)
return -EREMOTE;

full_path = build_unc_path_to_root(volume_info, cifs_sb);
full_path = build_unc_path_to_root(volume_info, cifs_sb, true);
if (IS_ERR(full_path))
return PTR_ERR(full_path);

Expand Down Expand Up @@ -3971,6 +3972,143 @@ expand_dfs_referral(const unsigned int xid, struct cifs_ses *ses,
kfree(full_path);
return rc;
}

static inline int get_next_dfs_tgt(const char *path,
struct dfs_cache_tgt_list *tgt_list,
struct dfs_cache_tgt_iterator **tgt_it)
{
if (!*tgt_it)
*tgt_it = dfs_cache_get_tgt_iterator(tgt_list);
else
*tgt_it = dfs_cache_get_next_tgt(tgt_list, *tgt_it);
return !*tgt_it ? -EHOSTDOWN : 0;
}

static int update_vol_info(const struct dfs_cache_tgt_iterator *tgt_it,
struct smb_vol *fake_vol, struct smb_vol *vol)
{
const char *tgt = dfs_cache_get_tgt_name(tgt_it);
int len = strlen(tgt) + 2;
char *new_unc;

new_unc = kmalloc(len, GFP_KERNEL);
if (!new_unc)
return -ENOMEM;
snprintf(new_unc, len, "\\%s", tgt);

kfree(vol->UNC);
vol->UNC = new_unc;

if (fake_vol->prepath) {
kfree(vol->prepath);
vol->prepath = fake_vol->prepath;
fake_vol->prepath = NULL;
}
memcpy(&vol->dstaddr, &fake_vol->dstaddr, sizeof(vol->dstaddr));

return 0;
}

static int setup_dfs_tgt_conn(const char *path,
const struct dfs_cache_tgt_iterator *tgt_it,
struct cifs_sb_info *cifs_sb,
struct smb_vol *vol,
unsigned int *xid,
struct TCP_Server_Info **server,
struct cifs_ses **ses,
struct cifs_tcon **tcon)
{
int rc;
struct dfs_info3_param ref = {0};
char *mdata = NULL, *fake_devname = NULL;
struct smb_vol fake_vol = {0};

cifs_dbg(FYI, "%s: dfs path: %s\n", __func__, path);

rc = dfs_cache_get_tgt_referral(path, tgt_it, &ref);
if (rc)
return rc;

mdata = cifs_compose_mount_options(cifs_sb->mountdata, path, &ref,
&fake_devname);
free_dfs_info_param(&ref);

if (IS_ERR(mdata)) {
rc = PTR_ERR(mdata);
mdata = NULL;
} else {
cifs_dbg(FYI, "%s: fake_devname: %s\n", __func__, fake_devname);
rc = cifs_setup_volume_info(&fake_vol, mdata, fake_devname,
false);
}
kfree(mdata);
kfree(fake_devname);

if (!rc) {
/*
* We use a 'fake_vol' here because we need pass it down to the
* mount_{get,put} functions to test connection against new DFS
* targets.
*/
mount_put_conns(cifs_sb, *xid, *server, *ses, *tcon);
rc = mount_get_conns(&fake_vol, cifs_sb, xid, server, ses,
tcon);
if (!rc) {
/*
* We were able to connect to new target server.
* Update current volume info with new target server.
*/
rc = update_vol_info(tgt_it, &fake_vol, vol);
}
}
cifs_cleanup_volume_info_contents(&fake_vol);
return rc;
}

static int mount_do_dfs_failover(const char *path,
struct cifs_sb_info *cifs_sb,
struct smb_vol *vol,
struct cifs_ses *root_ses,
unsigned int *xid,
struct TCP_Server_Info **server,
struct cifs_ses **ses,
struct cifs_tcon **tcon)
{
int rc;
struct dfs_cache_tgt_list tgt_list;
struct dfs_cache_tgt_iterator *tgt_it = NULL;

if (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_NO_DFS)
return -EOPNOTSUPP;

rc = dfs_cache_noreq_find(path, NULL, &tgt_list);
if (rc)
return rc;

for (;;) {
/* Get next DFS target server - if any */
rc = get_next_dfs_tgt(path, &tgt_list, &tgt_it);
if (rc)
break;
/* Connect to next DFS target */
rc = setup_dfs_tgt_conn(path, tgt_it, cifs_sb, vol, xid, server,
ses, tcon);
if (!rc || rc == -EACCES || rc == -EOPNOTSUPP)
break;
}
if (!rc) {
/*
* Update DFS target hint in DFS referral cache with the target
* server we successfully reconnected to.
*/
rc = dfs_cache_update_tgthint(*xid, root_ses ? root_ses : *ses,
cifs_sb->local_nls,
cifs_remap(cifs_sb), path,
tgt_it);
}
dfs_cache_free_tgts(&tgt_list);
return rc;
}
#endif

static int
Expand Down Expand Up @@ -4123,22 +4261,47 @@ int cifs_mount(struct cifs_sb_info *cifs_sb, struct smb_vol *vol)
int rc = 0;
unsigned int xid;
struct cifs_ses *ses;
struct cifs_tcon *root_tcon = NULL;
struct cifs_tcon *tcon = NULL;
struct TCP_Server_Info *server;
char *root_path = NULL, *full_path = NULL;
char *old_mountdata;
int count;

rc = mount_get_conns(vol, cifs_sb, &xid, &server, &ses, &tcon);
if (!rc && tcon) {
rc = is_path_remote(cifs_sb, vol, xid, server, tcon);
if (!rc)
goto out;
if (rc != -EREMOTE)
goto error;
/* If not a standalone DFS root, then check if path is remote */
rc = dfs_cache_find(xid, ses, cifs_sb->local_nls,
cifs_remap(cifs_sb), vol->UNC + 1, NULL,
NULL);
if (rc) {
rc = is_path_remote(cifs_sb, vol, xid, server, tcon);
if (!rc)
goto out;
if (rc != -EREMOTE)
goto error;
}
}
if ((rc == -EACCES) || (rc == -EOPNOTSUPP) || (ses == NULL) || (server == NULL))
/*
* If first DFS target server went offline and we failed to connect it,
* server and ses pointers are NULL at this point, though we still have
* chance to get a cached DFS referral in expand_dfs_referral() and
* retry next target available in it.
*
* If a NULL ses ptr is passed to dfs_cache_find(), a lookup will be
* performed against DFS path and *no* requests will be sent to server
* for any new DFS referrals. Hence it's safe to skip checking whether
* server or ses ptr is NULL.
*/
if (rc == -EACCES || rc == -EOPNOTSUPP)
goto error;

root_path = build_unc_path_to_root(vol, cifs_sb, false);
if (IS_ERR(root_path)) {
rc = PTR_ERR(root_path);
root_path = NULL;
goto error;
}

/*
* Perform an unconditional check for whether there are DFS
Expand All @@ -4163,8 +4326,36 @@ int cifs_mount(struct cifs_sb_info *cifs_sb, struct smb_vol *vol)
if (rc) {
if (rc == -EACCES || rc == -EOPNOTSUPP)
goto error;
/* Perform DFS failover to any other DFS targets */
rc = mount_do_dfs_failover(root_path + 1, cifs_sb, vol, NULL,
&xid, &server, &ses, &tcon);
if (rc)
goto error;
}

kfree(root_path);
root_path = build_unc_path_to_root(vol, cifs_sb, false);
if (IS_ERR(root_path)) {
rc = PTR_ERR(root_path);
root_path = NULL;
goto error;
}
/* Cache out resolved root server */
(void)dfs_cache_find(xid, ses, cifs_sb->local_nls, cifs_remap(cifs_sb),
root_path + 1, NULL, NULL);
/*
* Save root tcon for additional DFS requests to update or create a new
* DFS cache entry, or even perform DFS failover.
*/
spin_lock(&cifs_tcp_ses_lock);
tcon->tc_count++;
tcon->dfs_path = root_path;
root_path = NULL;
tcon->remap = cifs_remap(cifs_sb);
spin_unlock(&cifs_tcp_ses_lock);

root_tcon = tcon;

for (count = 1; ;) {
if (!rc && tcon) {
rc = is_path_remote(cifs_sb, vol, xid, server, tcon);
Expand All @@ -4182,8 +4373,16 @@ int cifs_mount(struct cifs_sb_info *cifs_sb, struct smb_vol *vol)
break;
}

kfree(full_path);
full_path = build_unc_path_to_root(vol, cifs_sb, true);
if (IS_ERR(full_path)) {
rc = PTR_ERR(full_path);
full_path = NULL;
break;
}

old_mountdata = cifs_sb->mountdata;
rc = expand_dfs_referral(xid, tcon->ses, vol, cifs_sb,
rc = expand_dfs_referral(xid, root_tcon->ses, vol, cifs_sb,
true);
if (rc)
break;
Expand All @@ -4194,11 +4393,18 @@ int cifs_mount(struct cifs_sb_info *cifs_sb, struct smb_vol *vol)
&tcon);
}
if (rc) {
if (rc == -EACCES || rc == -EOPNOTSUPP)
break;
/* Perform DFS failover to any other DFS targets */
rc = mount_do_dfs_failover(full_path + 1, cifs_sb, vol,
root_tcon->ses, &xid,
&server, &ses, &tcon);
if (rc == -EACCES || rc == -EOPNOTSUPP || !server ||
!ses)
goto error;
}
}
cifs_put_tcon(root_tcon);

if (rc)
goto error;
Expand All @@ -4214,6 +4420,8 @@ int cifs_mount(struct cifs_sb_info *cifs_sb, struct smb_vol *vol)
return mount_setup_tlink(cifs_sb, ses, tcon);

error:
kfree(full_path);
kfree(root_path);
mount_put_conns(cifs_sb, xid, server, ses, tcon);
return rc;
}
Expand Down
3 changes: 3 additions & 0 deletions fs/cifs/misc.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -146,6 +146,9 @@ tconInfoFree(struct cifs_tcon *buf_to_free)
kfree(buf_to_free->nativeFileSystem);
kzfree(buf_to_free->password);
kfree(buf_to_free->crfid.fid);
#ifdef CONFIG_CIFS_DFS_UPCALL
kfree(buf_to_free->dfs_path);
#endif
kfree(buf_to_free);
}

Expand Down

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