From patchwork Mon Oct 7 17:43:48 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Al Viro X-Patchwork-Id: 13825083 Received: from zeniv.linux.org.uk (zeniv.linux.org.uk [62.89.141.173]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 580F11DDA06 for ; Mon, 7 Oct 2024 17:44:00 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=62.89.141.173 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728323043; cv=none; b=YmdOmN8eiPfwSDIczRC/I9M48wqJI7bACAZyi1+pbNhquy5f2CAEd9g2EcFLUV8SxujHMFRuqRf2qLjjtSJdBvk5CiM+cKJNERESeKDxxpGWd8YxxFc7lC9w66rtEVTiYbBghzkhymIVLI/wSXT1QXfUvnotspv420CtI5ULTFs= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728323043; c=relaxed/simple; bh=6TRRMDmnfZBqlc7AUI509/Y5z00ehFW9CoNadZxXsI0=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Nv5bt/As3vZkgHh0JEd9fSYOTXySJw2lCvc2yL3WIfyqgN6Fu+8v1HTkvv6B5W1YLnDjMR3Yjalo5APi2H/zXoCFmCBzX8/FHwI+EFmYeJa7scEjyfeN/WWdV5UsIlAMpuKqlmhH28RAji1TCt9jy/798RLb8nWXNR1I8fcoq8g= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=zeniv.linux.org.uk; spf=none smtp.mailfrom=ftp.linux.org.uk; dkim=pass (2048-bit key) header.d=linux.org.uk header.i=@linux.org.uk header.b=oBeVqQsR; arc=none smtp.client-ip=62.89.141.173 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=zeniv.linux.org.uk Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=ftp.linux.org.uk Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=linux.org.uk header.i=@linux.org.uk header.b="oBeVqQsR" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=linux.org.uk; s=zeniv-20220401; h=Sender:Content-Transfer-Encoding: MIME-Version:References:In-Reply-To:Message-ID:Date:Subject:Cc:To:From: Reply-To:Content-Type:Content-ID:Content-Description; bh=G+aoWs+gSYe/WGxc8PAi13VMbRT7lF4Ka2Efl3I1ErY=; b=oBeVqQsRQBGdaK9WgMdVoIMjCM /QEjaBQz2bXWpfvo6dscflnsxL+IiSsb945jbVwuafyvMLrZ8Bjqr9IDAQAA5MjAE7hJ/LBoJDNkE 7F2/uKSq1tx99WB1fn5LIlXKsras8uuHK1SHtzBZbFj9Ga4rb4/WEO4EexppFSpMp9quxe6lx/7dh q3Bc2ydTG2eE0QbGAYzW0rs7IgBinX6PRzJoV/6PYzJJFjfOqSKj6gp2uVxB7pQJ0QzbmIWF70HX1 3q4SAEqxuTTiI4GdnNEFRQAQbTZrhburkfhnUXFSq2sUoC02DXyQ9u5WvPB5VX7gOghXjNT67lYb7 xsbjO5+Q==; Received: from viro by zeniv.linux.org.uk with local (Exim 4.98 #2 (Red Hat Linux)) id 1sxrm2-00000001f33-3ufP; Mon, 07 Oct 2024 17:43:58 +0000 From: Al Viro To: linux-fsdevel@vger.kernel.org Cc: torvalds@linux-foundation.org, brauner@kernel.org Subject: [PATCH v3 01/11] get rid of ...lookup...fdget_rcu() family Date: Mon, 7 Oct 2024 18:43:48 +0100 Message-ID: <20241007174358.396114-1-viro@zeniv.linux.org.uk> X-Mailer: git-send-email 2.46.2 In-Reply-To: <20241007173912.GR4017910@ZenIV> References: <20241007173912.GR4017910@ZenIV> Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Sender: Al Viro Once upon a time, predecessors of those used to do file lookup without bumping a refcount, provided that caller held rcu_read_lock() across the lookup and whatever it wanted to read from the struct file found. When struct file allocation switched to SLAB_TYPESAFE_BY_RCU, that stopped being feasible and these primitives started to bump the file refcount for lookup result, requiring the caller to call fput() afterwards. But that turned them pointless - e.g. rcu_read_lock(); file = lookup_fdget_rcu(fd); rcu_read_unlock(); is equivalent to file = fget_raw(fd); and all callers of lookup_fdget_rcu() are of that form. Similarly, task_lookup_fdget_rcu() calls can be replaced with calling fget_task(). task_lookup_next_fdget_rcu() doesn't have direct counterparts, but its callers would be happier if we replaced it with an analogue that deals with RCU internally. Reviewed-by: Christian Brauner Signed-off-by: Al Viro --- arch/powerpc/platforms/cell/spufs/coredump.c | 4 +-- fs/file.c | 28 +++----------------- fs/gfs2/glock.c | 12 ++------- fs/notify/dnotify/dnotify.c | 5 +--- fs/proc/fd.c | 12 +++------ include/linux/fdtable.h | 4 --- include/linux/file.h | 1 + kernel/bpf/task_iter.c | 6 +---- kernel/kcmp.c | 4 +-- 9 files changed, 14 insertions(+), 62 deletions(-) diff --git a/arch/powerpc/platforms/cell/spufs/coredump.c b/arch/powerpc/platforms/cell/spufs/coredump.c index 18daafbe2e65..301ee7d8b7df 100644 --- a/arch/powerpc/platforms/cell/spufs/coredump.c +++ b/arch/powerpc/platforms/cell/spufs/coredump.c @@ -73,9 +73,7 @@ static struct spu_context *coredump_next_context(int *fd) return NULL; *fd = n - 1; - rcu_read_lock(); - file = lookup_fdget_rcu(*fd); - rcu_read_unlock(); + file = fget_raw(*fd); if (file) { ctx = SPUFS_I(file_inode(file))->i_ctx; get_spu_context(ctx); diff --git a/fs/file.c b/fs/file.c index eb093e736972..991860ee7848 100644 --- a/fs/file.c +++ b/fs/file.c @@ -1037,29 +1037,7 @@ struct file *fget_task(struct task_struct *task, unsigned int fd) return file; } -struct file *lookup_fdget_rcu(unsigned int fd) -{ - return __fget_files_rcu(current->files, fd, 0); - -} -EXPORT_SYMBOL_GPL(lookup_fdget_rcu); - -struct file *task_lookup_fdget_rcu(struct task_struct *task, unsigned int fd) -{ - /* Must be called with rcu_read_lock held */ - struct files_struct *files; - struct file *file = NULL; - - task_lock(task); - files = task->files; - if (files) - file = __fget_files_rcu(files, fd, 0); - task_unlock(task); - - return file; -} - -struct file *task_lookup_next_fdget_rcu(struct task_struct *task, unsigned int *ret_fd) +struct file *fget_task_next(struct task_struct *task, unsigned int *ret_fd) { /* Must be called with rcu_read_lock held */ struct files_struct *files; @@ -1069,17 +1047,19 @@ struct file *task_lookup_next_fdget_rcu(struct task_struct *task, unsigned int * task_lock(task); files = task->files; if (files) { + rcu_read_lock(); for (; fd < files_fdtable(files)->max_fds; fd++) { file = __fget_files_rcu(files, fd, 0); if (file) break; } + rcu_read_unlock(); } task_unlock(task); *ret_fd = fd; return file; } -EXPORT_SYMBOL(task_lookup_next_fdget_rcu); +EXPORT_SYMBOL(fget_task_next); /* * Lightweight file lookup - no refcnt increment if fd table isn't shared. diff --git a/fs/gfs2/glock.c b/fs/gfs2/glock.c index 269c3bc7fced..4701c4aafbf4 100644 --- a/fs/gfs2/glock.c +++ b/fs/gfs2/glock.c @@ -34,7 +34,6 @@ #include #include #include -#include #include #include "gfs2.h" @@ -2768,25 +2767,18 @@ static struct file *gfs2_glockfd_next_file(struct gfs2_glockfd_iter *i) i->file = NULL; } - rcu_read_lock(); for(;; i->fd++) { - struct inode *inode; - - i->file = task_lookup_next_fdget_rcu(i->task, &i->fd); + i->file = fget_task_next(i->task, &i->fd); if (!i->file) { i->fd = 0; break; } - inode = file_inode(i->file); - if (inode->i_sb == i->sb) + if (file_inode(i->file)->i_sb == i->sb) break; - rcu_read_unlock(); fput(i->file); - rcu_read_lock(); } - rcu_read_unlock(); return i->file; } diff --git a/fs/notify/dnotify/dnotify.c b/fs/notify/dnotify/dnotify.c index d5dbef7f5c95..6004dfdfdf0f 100644 --- a/fs/notify/dnotify/dnotify.c +++ b/fs/notify/dnotify/dnotify.c @@ -16,7 +16,6 @@ #include #include #include -#include #include static int dir_notify_enable __read_mostly = 1; @@ -347,9 +346,7 @@ int fcntl_dirnotify(int fd, struct file *filp, unsigned int arg) new_fsn_mark = NULL; } - rcu_read_lock(); - f = lookup_fdget_rcu(fd); - rcu_read_unlock(); + f = fget_raw(fd); /* if (f != filp) means that we lost a race and another task/thread * actually closed the fd we are still playing with before we grabbed diff --git a/fs/proc/fd.c b/fs/proc/fd.c index 1f54a54bfb91..18d0dddc8e2f 100644 --- a/fs/proc/fd.c +++ b/fs/proc/fd.c @@ -116,9 +116,7 @@ static bool tid_fd_mode(struct task_struct *task, unsigned fd, fmode_t *mode) { struct file *file; - rcu_read_lock(); - file = task_lookup_fdget_rcu(task, fd); - rcu_read_unlock(); + file = fget_task(task, fd); if (file) { *mode = file->f_mode; fput(file); @@ -258,19 +256,17 @@ static int proc_readfd_common(struct file *file, struct dir_context *ctx, if (!dir_emit_dots(file, ctx)) goto out; - rcu_read_lock(); for (fd = ctx->pos - 2;; fd++) { struct file *f; struct fd_data data; char name[10 + 1]; unsigned int len; - f = task_lookup_next_fdget_rcu(p, &fd); + f = fget_task_next(p, &fd); ctx->pos = fd + 2LL; if (!f) break; data.mode = f->f_mode; - rcu_read_unlock(); fput(f); data.fd = fd; @@ -278,11 +274,9 @@ static int proc_readfd_common(struct file *file, struct dir_context *ctx, if (!proc_fill_cache(file, ctx, name, len, instantiate, p, &data)) - goto out; + break; cond_resched(); - rcu_read_lock(); } - rcu_read_unlock(); out: put_task_struct(p); return 0; diff --git a/include/linux/fdtable.h b/include/linux/fdtable.h index b1c5722f2b3c..e25e2cb65d30 100644 --- a/include/linux/fdtable.h +++ b/include/linux/fdtable.h @@ -92,10 +92,6 @@ static inline struct file *files_lookup_fd_locked(struct files_struct *files, un return files_lookup_fd_raw(files, fd); } -struct file *lookup_fdget_rcu(unsigned int fd); -struct file *task_lookup_fdget_rcu(struct task_struct *task, unsigned int fd); -struct file *task_lookup_next_fdget_rcu(struct task_struct *task, unsigned int *fd); - static inline bool close_on_exec(unsigned int fd, const struct files_struct *files) { return test_bit(fd, files_fdtable(files)->close_on_exec); diff --git a/include/linux/file.h b/include/linux/file.h index f98de143245a..ec4ad5e6a061 100644 --- a/include/linux/file.h +++ b/include/linux/file.h @@ -72,6 +72,7 @@ static inline void fdput(struct fd fd) extern struct file *fget(unsigned int fd); extern struct file *fget_raw(unsigned int fd); extern struct file *fget_task(struct task_struct *task, unsigned int fd); +extern struct file *fget_task_next(struct task_struct *task, unsigned int *fd); extern void __f_unlock_pos(struct file *); struct fd fdget(unsigned int fd); diff --git a/kernel/bpf/task_iter.c b/kernel/bpf/task_iter.c index 02aa9db8d796..7fe602ca74a0 100644 --- a/kernel/bpf/task_iter.c +++ b/kernel/bpf/task_iter.c @@ -5,7 +5,6 @@ #include #include #include -#include #include #include #include @@ -286,17 +285,14 @@ task_file_seq_get_next(struct bpf_iter_seq_task_file_info *info) curr_fd = 0; } - rcu_read_lock(); - f = task_lookup_next_fdget_rcu(curr_task, &curr_fd); + f = fget_task_next(curr_task, &curr_fd); if (f) { /* set info->fd */ info->fd = curr_fd; - rcu_read_unlock(); return f; } /* the current task is done, go to the next task */ - rcu_read_unlock(); put_task_struct(curr_task); if (info->common.type == BPF_TASK_ITER_TID) { diff --git a/kernel/kcmp.c b/kernel/kcmp.c index b0639f21041f..2c596851f8a9 100644 --- a/kernel/kcmp.c +++ b/kernel/kcmp.c @@ -63,9 +63,7 @@ get_file_raw_ptr(struct task_struct *task, unsigned int idx) { struct file *file; - rcu_read_lock(); - file = task_lookup_fdget_rcu(task, idx); - rcu_read_unlock(); + file = fget_task(task, idx); if (file) fput(file);