From 0de43976fbe716379084f954b1e370c35aa87bf0 Mon Sep 17 00:00:00 2001 From: Trond Myklebust Date: Sun, 2 Sep 2018 15:57:01 -0400 Subject: [PATCH] NFS: Convert lookups of the open context to RCU Reduce contention on the inode->i_lock by ensuring that we use RCU when looking up the NFS open context. Signed-off-by: Trond Myklebust --- fs/nfs/delegation.c | 11 ++++++----- fs/nfs/inode.c | 35 +++++++++++++++-------------------- fs/nfs/nfs4proc.c | 30 ++++++++++++++++++++++++------ fs/nfs/nfs4state.c | 12 ++++++------ fs/nfs/pnfs.c | 5 ++++- include/linux/nfs_fs.h | 1 + 6 files changed, 56 insertions(+), 38 deletions(-) diff --git a/fs/nfs/delegation.c b/fs/nfs/delegation.c index f033f3a69a3b..76d205d1c7bc 100644 --- a/fs/nfs/delegation.c +++ b/fs/nfs/delegation.c @@ -136,8 +136,8 @@ static int nfs_delegation_claim_opens(struct inode *inode, int err; again: - spin_lock(&inode->i_lock); - list_for_each_entry(ctx, &nfsi->open_files, list) { + rcu_read_lock(); + list_for_each_entry_rcu(ctx, &nfsi->open_files, list) { state = ctx->state; if (state == NULL) continue; @@ -147,8 +147,9 @@ again: continue; if (!nfs4_stateid_match(&state->stateid, stateid)) continue; - get_nfs_open_context(ctx); - spin_unlock(&inode->i_lock); + if (!get_nfs_open_context(ctx)) + continue; + rcu_read_unlock(); sp = state->owner; /* Block nfs4_proc_unlck */ mutex_lock(&sp->so_delegreturn_mutex); @@ -164,7 +165,7 @@ again: return err; goto again; } - spin_unlock(&inode->i_lock); + rcu_read_unlock(); return 0; } diff --git a/fs/nfs/inode.c b/fs/nfs/inode.c index 052db41a7f80..5b1eee4952b7 100644 --- a/fs/nfs/inode.c +++ b/fs/nfs/inode.c @@ -977,9 +977,9 @@ EXPORT_SYMBOL_GPL(alloc_nfs_open_context); struct nfs_open_context *get_nfs_open_context(struct nfs_open_context *ctx) { - if (ctx != NULL) - refcount_inc(&ctx->lock_context.count); - return ctx; + if (ctx != NULL && refcount_inc_not_zero(&ctx->lock_context.count)) + return ctx; + return NULL; } EXPORT_SYMBOL_GPL(get_nfs_open_context); @@ -988,13 +988,13 @@ static void __put_nfs_open_context(struct nfs_open_context *ctx, int is_sync) struct inode *inode = d_inode(ctx->dentry); struct super_block *sb = ctx->dentry->d_sb; + if (!refcount_dec_and_test(&ctx->lock_context.count)) + return; if (!list_empty(&ctx->list)) { - if (!refcount_dec_and_lock(&ctx->lock_context.count, &inode->i_lock)) - return; - list_del(&ctx->list); + spin_lock(&inode->i_lock); + list_del_rcu(&ctx->list); spin_unlock(&inode->i_lock); - } else if (!refcount_dec_and_test(&ctx->lock_context.count)) - return; + } if (inode != NULL) NFS_PROTO(inode)->close_context(ctx, is_sync); if (ctx->cred != NULL) @@ -1002,7 +1002,7 @@ static void __put_nfs_open_context(struct nfs_open_context *ctx, int is_sync) dput(ctx->dentry); nfs_sb_deactive(sb); kfree(ctx->mdsthreshold); - kfree(ctx); + kfree_rcu(ctx, rcu_head); } void put_nfs_open_context(struct nfs_open_context *ctx) @@ -1026,10 +1026,7 @@ void nfs_inode_attach_open_context(struct nfs_open_context *ctx) struct nfs_inode *nfsi = NFS_I(inode); spin_lock(&inode->i_lock); - if (ctx->mode & FMODE_WRITE) - list_add(&ctx->list, &nfsi->open_files); - else - list_add_tail(&ctx->list, &nfsi->open_files); + list_add_tail_rcu(&ctx->list, &nfsi->open_files); spin_unlock(&inode->i_lock); } EXPORT_SYMBOL_GPL(nfs_inode_attach_open_context); @@ -1050,16 +1047,17 @@ struct nfs_open_context *nfs_find_open_context(struct inode *inode, struct rpc_c struct nfs_inode *nfsi = NFS_I(inode); struct nfs_open_context *pos, *ctx = NULL; - spin_lock(&inode->i_lock); - list_for_each_entry(pos, &nfsi->open_files, list) { + rcu_read_lock(); + list_for_each_entry_rcu(pos, &nfsi->open_files, list) { if (cred != NULL && pos->cred != cred) continue; if ((pos->mode & (FMODE_READ|FMODE_WRITE)) != mode) continue; ctx = get_nfs_open_context(pos); - break; + if (ctx) + break; } - spin_unlock(&inode->i_lock); + rcu_read_unlock(); return ctx; } @@ -1077,9 +1075,6 @@ void nfs_file_clear_open_context(struct file *filp) if (ctx->error < 0) invalidate_inode_pages2(inode->i_mapping); filp->private_data = NULL; - spin_lock(&inode->i_lock); - list_move_tail(&ctx->list, &NFS_I(inode)->open_files); - spin_unlock(&inode->i_lock); put_nfs_open_context_sync(ctx); } } diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c index 8220a168282e..10c20a5b075d 100644 --- a/fs/nfs/nfs4proc.c +++ b/fs/nfs/nfs4proc.c @@ -1933,23 +1933,41 @@ nfs4_opendata_to_nfs4_state(struct nfs4_opendata *data) return ret; } -static struct nfs_open_context *nfs4_state_find_open_context(struct nfs4_state *state) +static struct nfs_open_context * +nfs4_state_find_open_context_mode(struct nfs4_state *state, fmode_t mode) { struct nfs_inode *nfsi = NFS_I(state->inode); struct nfs_open_context *ctx; - spin_lock(&state->inode->i_lock); - list_for_each_entry(ctx, &nfsi->open_files, list) { + rcu_read_lock(); + list_for_each_entry_rcu(ctx, &nfsi->open_files, list) { if (ctx->state != state) continue; - get_nfs_open_context(ctx); - spin_unlock(&state->inode->i_lock); + if ((ctx->mode & mode) != mode) + continue; + if (!get_nfs_open_context(ctx)) + continue; + rcu_read_unlock(); return ctx; } - spin_unlock(&state->inode->i_lock); + rcu_read_unlock(); return ERR_PTR(-ENOENT); } +static struct nfs_open_context * +nfs4_state_find_open_context(struct nfs4_state *state) +{ + struct nfs_open_context *ctx; + + ctx = nfs4_state_find_open_context_mode(state, FMODE_READ|FMODE_WRITE); + if (!IS_ERR(ctx)) + return ctx; + ctx = nfs4_state_find_open_context_mode(state, FMODE_WRITE); + if (!IS_ERR(ctx)) + return ctx; + return nfs4_state_find_open_context_mode(state, FMODE_READ); +} + static struct nfs4_opendata *nfs4_open_recoverdata_alloc(struct nfs_open_context *ctx, struct nfs4_state *state, enum open_claim_type4 claim) { diff --git a/fs/nfs/nfs4state.c b/fs/nfs/nfs4state.c index 40a08cd483f0..be92ce4259e9 100644 --- a/fs/nfs/nfs4state.c +++ b/fs/nfs/nfs4state.c @@ -1437,8 +1437,8 @@ void nfs_inode_find_state_and_recover(struct inode *inode, struct nfs4_state *state; bool found = false; - spin_lock(&inode->i_lock); - list_for_each_entry(ctx, &nfsi->open_files, list) { + rcu_read_lock(); + list_for_each_entry_rcu(ctx, &nfsi->open_files, list) { state = ctx->state; if (state == NULL) continue; @@ -1456,7 +1456,7 @@ void nfs_inode_find_state_and_recover(struct inode *inode, nfs4_state_mark_reclaim_nograce(clp, state)) found = true; } - spin_unlock(&inode->i_lock); + rcu_read_unlock(); nfs_inode_find_delegation_state_and_recover(inode, stateid); if (found) @@ -1469,13 +1469,13 @@ static void nfs4_state_mark_open_context_bad(struct nfs4_state *state) struct nfs_inode *nfsi = NFS_I(inode); struct nfs_open_context *ctx; - spin_lock(&inode->i_lock); - list_for_each_entry(ctx, &nfsi->open_files, list) { + rcu_read_lock(); + list_for_each_entry_rcu(ctx, &nfsi->open_files, list) { if (ctx->state != state) continue; set_bit(NFS_CONTEXT_BAD, &ctx->flags); } - spin_unlock(&inode->i_lock); + rcu_read_unlock(); } static void nfs4_state_mark_recovery_failed(struct nfs4_state *state, int error) diff --git a/fs/nfs/pnfs.c b/fs/nfs/pnfs.c index c5672c02afd6..06cb90e9bc6e 100644 --- a/fs/nfs/pnfs.c +++ b/fs/nfs/pnfs.c @@ -1339,6 +1339,7 @@ bool pnfs_roc(struct inode *ino, if (!nfs_have_layout(ino)) return false; retry: + rcu_read_lock(); spin_lock(&ino->i_lock); lo = nfsi->layout; if (!lo || !pnfs_layout_is_valid(lo) || @@ -1349,6 +1350,7 @@ retry: pnfs_get_layout_hdr(lo); if (test_bit(NFS_LAYOUT_RETURN_LOCK, &lo->plh_flags)) { spin_unlock(&ino->i_lock); + rcu_read_unlock(); wait_on_bit(&lo->plh_flags, NFS_LAYOUT_RETURN, TASK_UNINTERRUPTIBLE); pnfs_put_layout_hdr(lo); @@ -1362,7 +1364,7 @@ retry: skip_read = true; } - list_for_each_entry(ctx, &nfsi->open_files, list) { + list_for_each_entry_rcu(ctx, &nfsi->open_files, list) { state = ctx->state; if (state == NULL) continue; @@ -1410,6 +1412,7 @@ retry: out_noroc: spin_unlock(&ino->i_lock); + rcu_read_unlock(); pnfs_layoutcommit_inode(ino, true); if (roc) { struct pnfs_layoutdriver_type *ld = NFS_SERVER(ino)->pnfs_curr_ld; diff --git a/include/linux/nfs_fs.h b/include/linux/nfs_fs.h index d2f4f88a0e66..6e0417c02279 100644 --- a/include/linux/nfs_fs.h +++ b/include/linux/nfs_fs.h @@ -83,6 +83,7 @@ struct nfs_open_context { struct list_head list; struct nfs4_threshold *mdsthreshold; + struct rcu_head rcu_head; }; struct nfs_open_dir_context { -- 2.11.0