From 6c6c1d63c243025956f061e67fff3a615aa0f6be Mon Sep 17 00:00:00 2001 From: David Howells Date: Thu, 25 Apr 2019 14:26:52 +0100 Subject: [PATCH] afs: Provide mount-time configurable byte-range file locking emulation Provide byte-range file locking emulation that can be configured at mount time to one of four modes: (1) flock=local. Locking is done locally only and no reference is made to the server. (2) flock=openafs. Byte-range locking is done locally only; whole-file locking is done with reference to the server. Whole-file locks cannot be upgraded unless the client holds an exclusive lock. (3) flock=strict. Byte-range and whole-file locking both require a sufficient whole-file lock on the server. (4) flock=write. As strict, but the client always gets an exclusive whole-file lock on the server. Signed-off-by: David Howells --- fs/afs/flock.c | 49 ++++++++++++++++++++++++++++++++------ fs/afs/fsclient.c | 2 +- fs/afs/internal.h | 14 +++++++++++ fs/afs/super.c | 27 +++++++++++++++++++++ fs/afs/yfsclient.c | 2 +- include/trace/events/afs.h | 35 +++++++++++++++++++++++++++ 6 files changed, 120 insertions(+), 9 deletions(-) diff --git a/fs/afs/flock.c b/fs/afs/flock.c index 325bf731d8dd..ef313f4c1d11 100644 --- a/fs/afs/flock.c +++ b/fs/afs/flock.c @@ -409,7 +409,7 @@ static void afs_defer_unlock(struct afs_vnode *vnode) * whether we think that we have a locking permit. */ static int afs_do_setlk_check(struct afs_vnode *vnode, struct key *key, - afs_lock_type_t type, bool can_sleep) + enum afs_flock_mode mode, afs_lock_type_t type) { afs_access_t access; int ret; @@ -437,13 +437,9 @@ static int afs_do_setlk_check(struct afs_vnode *vnode, struct key *key, if (type == AFS_LOCK_READ) { if (!(access & (AFS_ACE_INSERT | AFS_ACE_WRITE | AFS_ACE_LOCK))) return -EACCES; - if (vnode->status.lock_count == -1 && !can_sleep) - return -EAGAIN; /* Write locked */ } else { if (!(access & (AFS_ACE_INSERT | AFS_ACE_WRITE))) return -EACCES; - if (vnode->status.lock_count != 0 && !can_sleep) - return -EAGAIN; /* Locked */ } return 0; @@ -456,24 +452,48 @@ static int afs_do_setlk(struct file *file, struct file_lock *fl) { struct inode *inode = locks_inode(file); struct afs_vnode *vnode = AFS_FS_I(inode); + enum afs_flock_mode mode = AFS_FS_S(inode->i_sb)->flock_mode; afs_lock_type_t type; struct key *key = afs_file_key(file); + bool partial, no_server_lock = false; int ret; - _enter("{%llx:%llu},%u", vnode->fid.vid, vnode->fid.vnode, fl->fl_type); + if (mode == afs_flock_mode_unset) + mode = afs_flock_mode_openafs; + + _enter("{%llx:%llu},%llu-%llu,%u,%u", + vnode->fid.vid, vnode->fid.vnode, + fl->fl_start, fl->fl_end, fl->fl_type, mode); fl->fl_ops = &afs_lock_ops; INIT_LIST_HEAD(&fl->fl_u.afs.link); fl->fl_u.afs.state = AFS_LOCK_PENDING; + partial = (fl->fl_start != 0 || fl->fl_end != OFFSET_MAX); type = (fl->fl_type == F_RDLCK) ? AFS_LOCK_READ : AFS_LOCK_WRITE; + if (mode == afs_flock_mode_write && partial) + type = AFS_LOCK_WRITE; - ret = afs_do_setlk_check(vnode, key, type, fl->fl_flags & FL_SLEEP); + ret = afs_do_setlk_check(vnode, key, mode, type); if (ret < 0) return ret; trace_afs_flock_op(vnode, fl, afs_flock_op_set_lock); + /* AFS3 protocol only supports full-file locks and doesn't provide any + * method of upgrade/downgrade, so we need to emulate for partial-file + * locks. + * + * The OpenAFS client only gets a server lock for a full-file lock and + * keeps partial-file locks local. Allow this behaviour to be emulated + * (as the default). + */ + if (mode == afs_flock_mode_local || + (partial && mode == afs_flock_mode_openafs)) { + no_server_lock = true; + goto skip_server_lock; + } + spin_lock(&vnode->lock); list_add_tail(&fl->fl_u.afs.link, &vnode->pending_locks); @@ -502,6 +522,18 @@ static int afs_do_setlk(struct file *file, struct file_lock *fl) } } + if (vnode->lock_state == AFS_VNODE_LOCK_NONE && + !(fl->fl_flags & FL_SLEEP)) { + ret = -EAGAIN; + if (type == AFS_LOCK_READ) { + if (vnode->status.lock_count == -1) + goto lock_is_contended; /* Write locked */ + } else { + if (vnode->status.lock_count != 0) + goto lock_is_contended; /* Locked */ + } + } + if (vnode->lock_state != AFS_VNODE_LOCK_NONE) goto need_to_wait; @@ -571,6 +603,7 @@ vnode_is_locked: /* the lock has been granted by the server... */ ASSERTCMP(fl->fl_u.afs.state, ==, AFS_LOCK_GRANTED); +skip_server_lock: /* ... but the VFS still needs to distribute access on this client. */ trace_afs_flock_ev(vnode, fl, afs_flock_vfs_locking, 0); ret = locks_lock_file_wait(file, fl); @@ -649,6 +682,8 @@ vfs_rejected_lock: * deal with. */ _debug("vfs refused %d", ret); + if (no_server_lock) + goto error; spin_lock(&vnode->lock); list_del_init(&fl->fl_u.afs.link); afs_defer_unlock(vnode); diff --git a/fs/afs/fsclient.c b/fs/afs/fsclient.c index be4520eb4965..9b73a57aa5cb 100644 --- a/fs/afs/fsclient.c +++ b/fs/afs/fsclient.c @@ -1902,7 +1902,7 @@ int afs_fs_set_lock(struct afs_fs_cursor *fc, afs_lock_type_t type) *bp++ = htonl(type); afs_use_fs_server(call, fc->cbi); - trace_afs_make_fs_call(call, &vnode->fid); + trace_afs_make_fs_calli(call, &vnode->fid, type); afs_make_call(&fc->ac, call, GFP_NOFS); return afs_wait_for_call_to_complete(call, &fc->ac); } diff --git a/fs/afs/internal.h b/fs/afs/internal.h index 20fd44de26ac..91204e1428f2 100644 --- a/fs/afs/internal.h +++ b/fs/afs/internal.h @@ -36,11 +36,24 @@ struct pagevec; struct afs_call; +/* + * Partial file-locking emulation mode. (The problem being that AFS3 only + * allows whole-file locks and no upgrading/downgrading). + */ +enum afs_flock_mode { + afs_flock_mode_unset, + afs_flock_mode_local, /* Local locking only */ + afs_flock_mode_openafs, /* Don't get server lock for a partial lock */ + afs_flock_mode_strict, /* Always get a server lock for a partial lock */ + afs_flock_mode_write, /* Get an exclusive server lock for a partial lock */ +}; + struct afs_fs_context { bool force; /* T to force cell type */ bool autocell; /* T if set auto mount operation */ bool dyn_root; /* T if dynamic root */ bool no_cell; /* T if the source is "none" (for dynroot) */ + enum afs_flock_mode flock_mode; /* Partial file-locking emulation mode */ afs_voltype_t type; /* type of volume requested */ unsigned int volnamesz; /* size of volume name */ const char *volname; /* name of volume to mount */ @@ -221,6 +234,7 @@ struct afs_super_info { struct net *net_ns; /* Network namespace */ struct afs_cell *cell; /* The cell in which the volume resides */ struct afs_volume *volume; /* volume record */ + enum afs_flock_mode flock_mode:8; /* File locking emulation mode */ bool dyn_root; /* True if dynamic root */ }; diff --git a/fs/afs/super.c b/fs/afs/super.c index ce85ae61f12d..18334fa1a0d2 100644 --- a/fs/afs/super.c +++ b/fs/afs/super.c @@ -67,19 +67,30 @@ static atomic_t afs_count_active_inodes; enum afs_param { Opt_autocell, Opt_dyn, + Opt_flock, Opt_source, }; static const struct fs_parameter_spec afs_param_specs[] = { fsparam_flag ("autocell", Opt_autocell), fsparam_flag ("dyn", Opt_dyn), + fsparam_enum ("flock", Opt_flock), fsparam_string("source", Opt_source), {} }; +static const struct fs_parameter_enum afs_param_enums[] = { + { Opt_flock, "local", afs_flock_mode_local }, + { Opt_flock, "openafs", afs_flock_mode_openafs }, + { Opt_flock, "strict", afs_flock_mode_strict }, + { Opt_flock, "write", afs_flock_mode_write }, + {} +}; + static const struct fs_parameter_description afs_fs_parameters = { .name = "kAFS", .specs = afs_param_specs, + .enums = afs_param_enums, }; /* @@ -182,11 +193,22 @@ static int afs_show_devname(struct seq_file *m, struct dentry *root) static int afs_show_options(struct seq_file *m, struct dentry *root) { struct afs_super_info *as = AFS_FS_S(root->d_sb); + const char *p = NULL; if (as->dyn_root) seq_puts(m, ",dyn"); if (test_bit(AFS_VNODE_AUTOCELL, &AFS_FS_I(d_inode(root))->flags)) seq_puts(m, ",autocell"); + switch (as->flock_mode) { + case afs_flock_mode_unset: break; + case afs_flock_mode_local: p = "local"; break; + case afs_flock_mode_openafs: p = "openafs"; break; + case afs_flock_mode_strict: p = "strict"; break; + case afs_flock_mode_write: p = "write"; break; + } + if (p) + seq_printf(m, ",flock=%s", p); + return 0; } @@ -315,6 +337,10 @@ static int afs_parse_param(struct fs_context *fc, struct fs_parameter *param) ctx->dyn_root = true; break; + case Opt_flock: + ctx->flock_mode = result.uint_32; + break; + default: return -EINVAL; } @@ -466,6 +492,7 @@ static struct afs_super_info *afs_alloc_sbi(struct fs_context *fc) as = kzalloc(sizeof(struct afs_super_info), GFP_KERNEL); if (as) { as->net_ns = get_net(fc->net_ns); + as->flock_mode = ctx->flock_mode; if (ctx->dyn_root) { as->dyn_root = true; } else { diff --git a/fs/afs/yfsclient.c b/fs/afs/yfsclient.c index 5ea0350dc9dd..055840aa07f6 100644 --- a/fs/afs/yfsclient.c +++ b/fs/afs/yfsclient.c @@ -1860,7 +1860,7 @@ int yfs_fs_set_lock(struct afs_fs_cursor *fc, afs_lock_type_t type) yfs_check_req(call, bp); afs_use_fs_server(call, fc->cbi); - trace_afs_make_fs_call(call, &vnode->fid); + trace_afs_make_fs_calli(call, &vnode->fid, type); afs_make_call(&fc->ac, call, GFP_NOFS); return afs_wait_for_call_to_complete(call, &fc->ac); } diff --git a/include/trace/events/afs.h b/include/trace/events/afs.h index e81d6a50781f..f1373c29bf7d 100644 --- a/include/trace/events/afs.h +++ b/include/trace/events/afs.h @@ -539,6 +539,41 @@ TRACE_EVENT(afs_make_fs_call, __print_symbolic(__entry->op, afs_fs_operations)) ); +TRACE_EVENT(afs_make_fs_calli, + TP_PROTO(struct afs_call *call, const struct afs_fid *fid, + unsigned int i), + + TP_ARGS(call, fid, i), + + TP_STRUCT__entry( + __field(unsigned int, call ) + __field(unsigned int, i ) + __field(enum afs_fs_operation, op ) + __field_struct(struct afs_fid, fid ) + ), + + TP_fast_assign( + __entry->call = call->debug_id; + __entry->i = i; + __entry->op = call->operation_ID; + if (fid) { + __entry->fid = *fid; + } else { + __entry->fid.vid = 0; + __entry->fid.vnode = 0; + __entry->fid.unique = 0; + } + ), + + TP_printk("c=%08x %06llx:%06llx:%06x %s i=%u", + __entry->call, + __entry->fid.vid, + __entry->fid.vnode, + __entry->fid.unique, + __print_symbolic(__entry->op, afs_fs_operations), + __entry->i) + ); + TRACE_EVENT(afs_make_fs_call1, TP_PROTO(struct afs_call *call, const struct afs_fid *fid, const char *name), -- 2.30.2