I'm not completely sure I understand, but it looks to me like it still has the flaw Al described: you're allowing the server to use the mount (and take further references on it) based only on having a pin. --b. On Sat, Jun 06, 2015 at 10:41:57PM +0800, Kinglong Mee wrote: > If there are some mount points(not exported for nfs) under pseudo root, > after client's operation of those entry under the root, anyone *can't* > unmount those mount points until export cache expired. > > /nfs/xfs *(rw,insecure,no_subtree_check,no_root_squash) > /nfs/pnfs *(rw,insecure,no_subtree_check,no_root_squash) > total 0 > drwxr-xr-x. 3 root root 84 Apr 21 22:27 pnfs > drwxr-xr-x. 3 root root 84 Apr 21 22:27 test > drwxr-xr-x. 2 root root 6 Apr 20 22:01 xfs > Filesystem 1K-blocks Used Available Use% Mounted on > ...... > /dev/sdd 1038336 32944 1005392 4% /nfs/pnfs > /dev/sdc 10475520 32928 10442592 1% /nfs/xfs > /dev/sde 999320 1284 929224 1% /nfs/test > /mnt/pnfs/: > total 0 > -rw-r--r--. 1 root root 0 Apr 21 22:23 attr > drwxr-xr-x. 2 root root 6 Apr 21 22:19 tmp > > /mnt/xfs/: > total 0 > umount: /nfs/test/: target is busy > (In some cases useful info about processes that > use the device is found by lsof(8) or fuser(1).) > > It's caused by exports cache of nfsd holds the reference of > the path (here is /nfs/test/), so, it can't be umounted. > > I don't think that's user expect, they want umount /nfs/test/. > Bruce think user can also umount /nfs/pnfs/ and /nfs/xfs. > > Also, using kzalloc for all memory allocating without kmalloc. > Thanks for Al Viro's commets for the logic of fs_pin. > > v3, > 1. using path_get_pin/path_put_unpin for path pin > 2. using kzalloc for memory allocating > > v4, > 1. add a completion for pin_kill waiting the reference is decreased to zero. > 2. add a work_struct for pin_kill decreases the reference indirectly. > 3. free svc_export/svc_expkey in pin_kill, not svc_export_put/svc_expkey_put. > 4. svc_export_put/svc_expkey_put go though pin_kill logic. > > Signed-off-by: Kinglong Mee <kinglongmee@xxxxxxxxx> > --- > fs/nfsd/export.c | 96 +++++++++++++++++++++++++++++++++++++++++++++----------- > fs/nfsd/export.h | 18 ++++++++++- > 2 files changed, 95 insertions(+), 19 deletions(-) > > diff --git a/fs/nfsd/export.c b/fs/nfsd/export.c > index f79521a..d3e59bc 100644 > --- a/fs/nfsd/export.c > +++ b/fs/nfsd/export.c > @@ -37,15 +37,23 @@ > #define EXPKEY_HASHMAX (1 << EXPKEY_HASHBITS) > #define EXPKEY_HASHMASK (EXPKEY_HASHMAX -1) > > +static void expkey_destroy(struct svc_expkey *key) > +{ > + auth_domain_put(key->ek_client); > + kfree_rcu(key, rcu_head); > +} > + > static void expkey_put(struct kref *ref) > { > struct svc_expkey *key = container_of(ref, struct svc_expkey, h.ref); > > if (test_bit(CACHE_VALID, &key->h.flags) && > - !test_bit(CACHE_NEGATIVE, &key->h.flags)) > - path_put(&key->ek_path); > - auth_domain_put(key->ek_client); > - kfree(key); > + !test_bit(CACHE_NEGATIVE, &key->h.flags)) { > + rcu_read_lock(); > + complete(&key->ek_done); > + pin_kill(&key->ek_pin); > + } else > + expkey_destroy(key); > } > > static void expkey_request(struct cache_detail *cd, > @@ -83,7 +91,7 @@ static int expkey_parse(struct cache_detail *cd, char *mesg, int mlen) > return -EINVAL; > mesg[mlen-1] = 0; > > - buf = kmalloc(PAGE_SIZE, GFP_KERNEL); > + buf = kzalloc(PAGE_SIZE, GFP_KERNEL); > err = -ENOMEM; > if (!buf) > goto out; > @@ -120,6 +128,7 @@ static int expkey_parse(struct cache_detail *cd, char *mesg, int mlen) > goto out; > > key.ek_client = dom; > + key.cd = cd; > key.ek_fsidtype = fsidtype; > memcpy(key.ek_fsid, buf, len); > > @@ -210,6 +219,25 @@ static inline void expkey_init(struct cache_head *cnew, > new->ek_fsidtype = item->ek_fsidtype; > > memcpy(new->ek_fsid, item->ek_fsid, sizeof(new->ek_fsid)); > + new->cd = item->cd; > +} > + > +static void expkey_pin_kill(struct fs_pin *pin) > +{ > + struct svc_expkey *key = container_of(pin, struct svc_expkey, ek_pin); > + > + if (!completion_done(&key->ek_done)) { > + schedule_work(&key->ek_work); > + wait_for_completion(&key->ek_done); > + } > + path_put_unpin(&key->ek_path, &key->ek_pin); > + expkey_destroy(key); > +} > + > +static void expkey_close_work(struct work_struct *work) > +{ > + struct svc_expkey *key = container_of(work, struct svc_expkey, ek_work); > + cache_force_expire(key->cd, &key->h); > } > > static inline void expkey_update(struct cache_head *cnew, > @@ -218,16 +246,19 @@ static inline void expkey_update(struct cache_head *cnew, > struct svc_expkey *new = container_of(cnew, struct svc_expkey, h); > struct svc_expkey *item = container_of(citem, struct svc_expkey, h); > > + init_fs_pin(&new->ek_pin, expkey_pin_kill); > new->ek_path = item->ek_path; > - path_get(&item->ek_path); > + path_get_pin(&new->ek_path, &new->ek_pin); > } > > static struct cache_head *expkey_alloc(void) > { > - struct svc_expkey *i = kmalloc(sizeof(*i), GFP_KERNEL); > - if (i) > + struct svc_expkey *i = kzalloc(sizeof(*i), GFP_KERNEL); > + if (i) { > + INIT_WORK(&i->ek_work, expkey_close_work); > + init_completion(&i->ek_done); > return &i->h; > - else > + } else > return NULL; > } > > @@ -306,14 +337,21 @@ static void nfsd4_fslocs_free(struct nfsd4_fs_locations *fsloc) > fsloc->locations = NULL; > } > > -static void svc_export_put(struct kref *ref) > +static void svc_export_destroy(struct svc_export *exp) > { > - struct svc_export *exp = container_of(ref, struct svc_export, h.ref); > - path_put(&exp->ex_path); > auth_domain_put(exp->ex_client); > nfsd4_fslocs_free(&exp->ex_fslocs); > kfree(exp->ex_uuid); > - kfree(exp); > + kfree_rcu(exp, rcu_head); > +} > + > +static void svc_export_put(struct kref *ref) > +{ > + struct svc_export *exp = container_of(ref, struct svc_export, h.ref); > + > + rcu_read_lock(); > + complete(&exp->ex_done); > + pin_kill(&exp->ex_pin); > } > > static void svc_export_request(struct cache_detail *cd, > @@ -520,7 +558,7 @@ static int svc_export_parse(struct cache_detail *cd, char *mesg, int mlen) > return -EINVAL; > mesg[mlen-1] = 0; > > - buf = kmalloc(PAGE_SIZE, GFP_KERNEL); > + buf = kzalloc(PAGE_SIZE, GFP_KERNEL); > if (!buf) > return -ENOMEM; > > @@ -694,15 +732,34 @@ static int svc_export_match(struct cache_head *a, struct cache_head *b) > path_equal(&orig->ex_path, &new->ex_path); > } > > +static void export_pin_kill(struct fs_pin *pin) > +{ > + struct svc_export *exp = container_of(pin, struct svc_export, ex_pin); > + > + if (!completion_done(&exp->ex_done)) { > + schedule_work(&exp->ex_work); > + wait_for_completion(&exp->ex_done); > + } > + path_put_unpin(&exp->ex_path, &exp->ex_pin); > + svc_export_destroy(exp); > +} > + > +static void export_close_work(struct work_struct *work) > +{ > + struct svc_export *exp = container_of(work, struct svc_export, ex_work); > + cache_force_expire(exp->cd, &exp->h); > +} > + > static void svc_export_init(struct cache_head *cnew, struct cache_head *citem) > { > struct svc_export *new = container_of(cnew, struct svc_export, h); > struct svc_export *item = container_of(citem, struct svc_export, h); > > + init_fs_pin(&new->ex_pin, export_pin_kill); > kref_get(&item->ex_client->ref); > new->ex_client = item->ex_client; > new->ex_path = item->ex_path; > - path_get(&item->ex_path); > + path_get_pin(&new->ex_path, &new->ex_pin); > new->ex_fslocs.locations = NULL; > new->ex_fslocs.locations_count = 0; > new->ex_fslocs.migrated = 0; > @@ -740,10 +797,12 @@ static void export_update(struct cache_head *cnew, struct cache_head *citem) > > static struct cache_head *svc_export_alloc(void) > { > - struct svc_export *i = kmalloc(sizeof(*i), GFP_KERNEL); > - if (i) > + struct svc_export *i = kzalloc(sizeof(*i), GFP_KERNEL); > + if (i) { > + INIT_WORK(&i->ex_work, export_close_work); > + init_completion(&i->ex_done); > return &i->h; > - else > + } else > return NULL; > } > > @@ -811,6 +870,7 @@ exp_find_key(struct cache_detail *cd, struct auth_domain *clp, int fsid_type, > > key.ek_client = clp; > key.ek_fsidtype = fsid_type; > + key.cd = cd; > memcpy(key.ek_fsid, fsidv, key_len(fsid_type)); > > ek = svc_expkey_lookup(cd, &key); > diff --git a/fs/nfsd/export.h b/fs/nfsd/export.h > index 1f52bfc..ff8905d 100644 > --- a/fs/nfsd/export.h > +++ b/fs/nfsd/export.h > @@ -4,6 +4,7 @@ > #ifndef NFSD_EXPORT_H > #define NFSD_EXPORT_H > > +#include <linux/fs_pin.h> > #include <linux/sunrpc/cache.h> > #include <uapi/linux/nfsd/export.h> > > @@ -46,6 +47,8 @@ struct exp_flavor_info { > > struct svc_export { > struct cache_head h; > + struct cache_detail *cd; > + > struct auth_domain * ex_client; > int ex_flags; > struct path ex_path; > @@ -58,7 +61,13 @@ struct svc_export { > struct exp_flavor_info ex_flavors[MAX_SECINFO_LIST]; > enum pnfs_layouttype ex_layout_type; > struct nfsd4_deviceid_map *ex_devid_map; > - struct cache_detail *cd; > + > + struct fs_pin ex_pin; > + struct rcu_head rcu_head; > + > + /* For cache_put and fs umounting window */ > + struct completion ex_done; > + struct work_struct ex_work; > }; > > /* an "export key" (expkey) maps a filehandlefragement to an > @@ -67,12 +76,19 @@ struct svc_export { > */ > struct svc_expkey { > struct cache_head h; > + struct cache_detail *cd; > > struct auth_domain * ek_client; > int ek_fsidtype; > u32 ek_fsid[6]; > > struct path ek_path; > + struct fs_pin ek_pin; > + struct rcu_head rcu_head; > + > + /* For cache_put and fs umounting window */ > + struct completion ek_done; > + struct work_struct ek_work; > }; > > #define EX_ISSYNC(exp) (!((exp)->ex_flags & NFSEXP_ASYNC)) > -- > 2.4.2 -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html