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afs: Change dynroot to create contents on demand

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Change the AFS dynamic root to do things differently:

 (1) Rather than having the creation of cell records create inodes and
     dentries for cell mountpoints, create them on demand during lookup.

     This simplifies cell management and locking as we no longer have to
     create these objects in advance *and* on speculative lookup by the
     user for a cell that isn't precreated.

 (2) Rather than using the libfs dentry-based readdir (the dentries now no
     longer exist until accessed from (1)), have readdir generate the
     contents by reading the list of cells.  The @cell symlinks get pushed
     in positions 2 and 3 if rootcell has been configured.

 (3) Make the @cell symlink dentries persist for the life of the superblock
     or until reclaimed, but make cell mountpoints disappear immediately if
     unused.

     It's not perfect as someone doing an "ls -l /afs" may create a whole
     bunch of dentries which will be garbage collected immediately.  But
     any dentry that gets automounted will be pinned by the mount, so it
     shouldn't be too bad.

 (4) Allocate the inode numbers for the cell mountpoints from an IDR to
     prevent duplicates appearing in the event it cycles round.  The number
     allocated from the IDR is doubled to provide two inode numbers - one
     for the normal cell name (RO) and one for the dotted cell name (RW).

Signed-off-by: David Howells <dhowells@redhat.com>
cc: Marc Dionne <marc.dionne@auristor.com>
cc: linux-afs@lists.infradead.org
cc: linux-fsdevel@vger.kernel.org
Link: https://lore.kernel.org/r/20250224234154.2014840-8-dhowells@redhat.com/ # v1
Link: https://lore.kernel.org/r/20250310094206.801057-4-dhowells@redhat.com/ # v4
This commit is contained in:
David Howells
2025-03-10 09:47:15 +00:00
parent 4c5ad63f85
commit 1d0b929fc0
6 changed files with 240 additions and 326 deletions
Download Patch File Download Diff File Expand all files Collapse all files
fs/afs/cell.c
+7 -2
View File
@@ -204,7 +204,13 @@ static struct afs_cell *afs_alloc_cell(struct afs_net *net,
cell->dns_status = vllist->status;
smp_store_release(&cell->dns_lookup_count, 1); /* vs source/status */
atomic_inc(&net->cells_outstanding);
ret = idr_alloc_cyclic(&net->cells_dyn_ino, cell,
2, INT_MAX / 2, GFP_KERNEL);
if (ret < 0)
goto error;
cell->dynroot_ino = ret;
cell->debug_id = atomic_inc_return(&cell_debug_id);
trace_afs_cell(cell->debug_id, 1, 0, afs_cell_trace_alloc);
_leave(" = %p", cell);
@@ -513,6 +519,7 @@ static void afs_cell_destroy(struct rcu_head *rcu)
afs_put_vlserverlist(net, rcu_access_pointer(cell->vl_servers));
afs_unuse_cell(net, cell->alias_of, afs_cell_trace_unuse_alias);
key_put(cell->anonymous_key);
idr_remove(&net->cells_dyn_ino, cell->dynroot_ino);
kfree(cell->name - 1);
kfree(cell);
@@ -706,7 +713,6 @@ static int afs_activate_cell(struct afs_net *net, struct afs_cell *cell)
if (cell->proc_link.next)
cell->proc_link.next->pprev = &cell->proc_link.next;
afs_dynroot_mkdir(net, cell);
mutex_unlock(&net->proc_cells_lock);
return 0;
}
@@ -723,7 +729,6 @@ static void afs_deactivate_cell(struct afs_net *net, struct afs_cell *cell)
mutex_lock(&net->proc_cells_lock);
if (!hlist_unhashed(&cell->proc_link))
hlist_del_rcu(&cell->proc_link);
afs_dynroot_rmdir(net, cell);
mutex_unlock(&net->proc_cells_lock);
_leave("");
fs/afs/dynroot.c
+224 -312
View File
File diff suppressed because it is too large Load Diff
fs/afs/internal.h
+3 -5
View File
@@ -287,6 +287,7 @@ struct afs_net {
/* Cell database */
struct rb_root cells;
struct idr cells_dyn_ino; /* cell->dynroot_ino mapping */
struct afs_cell __rcu *ws_cell;
struct work_struct cells_manager;
struct timer_list cells_timer;
@@ -398,6 +399,7 @@ struct afs_cell {
enum dns_lookup_status dns_status:8; /* Latest status of data from lookup */
unsigned int dns_lookup_count; /* Counter of DNS lookups */
unsigned int debug_id;
unsigned int dynroot_ino; /* Inode numbers for dynroot (a pair) */
/* The volumes belonging to this cell */
struct rw_semaphore vs_lock; /* Lock for server->volumes */
@@ -1110,10 +1112,7 @@ extern int afs_silly_iput(struct dentry *, struct inode *);
extern const struct inode_operations afs_dynroot_inode_operations;
extern const struct dentry_operations afs_dynroot_dentry_operations;
extern int afs_dynroot_mkdir(struct afs_net *, struct afs_cell *);
extern void afs_dynroot_rmdir(struct afs_net *, struct afs_cell *);
extern int afs_dynroot_populate(struct super_block *);
extern void afs_dynroot_depopulate(struct super_block *);
struct inode *afs_dynroot_iget_root(struct super_block *sb);
/*
* file.c
@@ -1226,7 +1225,6 @@ int afs_readlink(struct dentry *dentry, char __user *buffer, int buflen);
extern void afs_vnode_commit_status(struct afs_operation *, struct afs_vnode_param *);
extern int afs_fetch_status(struct afs_vnode *, struct key *, bool, afs_access_t *);
extern int afs_ilookup5_test_by_fid(struct inode *, void *);
extern struct inode *afs_iget_pseudo_dir(struct super_block *, bool);
extern struct inode *afs_iget(struct afs_operation *, struct afs_vnode_param *);
extern struct inode *afs_root_iget(struct super_block *, struct key *);
extern int afs_getattr(struct mnt_idmap *idmap, const struct path *,
fs/afs/main.c
+3
View File
@@ -76,6 +76,7 @@ static int __net_init afs_net_init(struct net *net_ns)
mutex_init(&net->socket_mutex);
net->cells = RB_ROOT;
idr_init(&net->cells_dyn_ino);
init_rwsem(&net->cells_lock);
INIT_WORK(&net->cells_manager, afs_manage_cells);
timer_setup(&net->cells_timer, afs_cells_timer, 0);
@@ -137,6 +138,7 @@ error_cell_init:
error_proc:
afs_put_sysnames(net->sysnames);
error_sysnames:
idr_destroy(&net->cells_dyn_ino);
net->live = false;
return ret;
}
@@ -155,6 +157,7 @@ static void __net_exit afs_net_exit(struct net *net_ns)
afs_close_socket(net);
afs_proc_cleanup(net);
afs_put_sysnames(net->sysnames);
idr_destroy(&net->cells_dyn_ino);
kfree_rcu(rcu_access_pointer(net->address_prefs), rcu);
}
fs/afs/super.c
+1 -7
View File
@@ -466,7 +466,7 @@ static int afs_fill_super(struct super_block *sb, struct afs_fs_context *ctx)
/* allocate the root inode and dentry */
if (as->dyn_root) {
inode = afs_iget_pseudo_dir(sb, true);
inode = afs_dynroot_iget_root(sb);
} else {
sprintf(sb->s_id, "%llu", as->volume->vid);
afs_activate_volume(as->volume);
@@ -483,9 +483,6 @@ static int afs_fill_super(struct super_block *sb, struct afs_fs_context *ctx)
if (as->dyn_root) {
sb->s_d_op = &afs_dynroot_dentry_operations;
ret = afs_dynroot_populate(sb);
if (ret < 0)
goto error;
} else {
sb->s_d_op = &afs_fs_dentry_operations;
rcu_assign_pointer(as->volume->sb, sb);
@@ -534,9 +531,6 @@ static void afs_kill_super(struct super_block *sb)
{
struct afs_super_info *as = AFS_FS_S(sb);
if (as->dyn_root)
afs_dynroot_depopulate(sb);
/* Clear the callback interests (which will do ilookup5) before
* deactivating the superblock.
*/
include/trace/events/afs.h
+2
View File
@@ -190,8 +190,10 @@ enum yfs_cm_operation {
EM(afs_cell_trace_unuse_alias, "UNU alias ") \
EM(afs_cell_trace_unuse_check_alias, "UNU chk-al") \
EM(afs_cell_trace_unuse_delete, "UNU delete") \
EM(afs_cell_trace_unuse_dynroot_mntpt, "UNU dyn-mp") \
EM(afs_cell_trace_unuse_fc, "UNU fc ") \
EM(afs_cell_trace_unuse_lookup, "UNU lookup") \
EM(afs_cell_trace_unuse_lookup_dynroot, "UNU lu-dyn") \
EM(afs_cell_trace_unuse_mntpt, "UNU mntpt ") \
EM(afs_cell_trace_unuse_no_pin, "UNU no-pin") \
EM(afs_cell_trace_unuse_parse, "UNU parse ") \