From patchwork Thu Jan 4 21:57:12 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Steven Rostedt X-Patchwork-Id: 13511586 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 111622C851; Thu, 4 Jan 2024 21:59:41 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id A76E5C433C8; Thu, 4 Jan 2024 21:59:41 +0000 (UTC) Received: from rostedt by gandalf with local (Exim 4.97) (envelope-from ) id 1rLVlg-00000000vgE-0dzN; Thu, 04 Jan 2024 17:00:48 -0500 Message-ID: <20240104220048.016261289@goodmis.org> User-Agent: quilt/0.67 Date: Thu, 04 Jan 2024 16:57:12 -0500 From: Steven Rostedt To: linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org Cc: Masami Hiramatsu , Mark Rutland , Mathieu Desnoyers , Andrew Morton , Linus Torvalds , Al Viro , Christian Brauner , linux-fsdevel@vger.kernel.org, Greg Kroah-Hartman Subject: [PATCH 1/4] eventfs: Have eventfs_iterate() stop immediately if ei->is_freed is set References: <20240104215711.924088454@goodmis.org> Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 From: "Steven Rostedt (Google)" If ei->is_freed is set in eventfs_iterate(), it means that the directory that is being iterated on is in the process of being freed. Just exit the loop immediately when that is ever detected, and separate out the return of the entry->callback() from ei->is_freed. Signed-off-by: Steven Rostedt (Google) --- fs/tracefs/event_inode.c | 11 ++++++----- 1 file changed, 6 insertions(+), 5 deletions(-) diff --git a/fs/tracefs/event_inode.c b/fs/tracefs/event_inode.c index 72912b5f9a90..0aca6910efb3 100644 --- a/fs/tracefs/event_inode.c +++ b/fs/tracefs/event_inode.c @@ -788,11 +788,12 @@ static int eventfs_iterate(struct file *file, struct dir_context *ctx) name = entry->name; mutex_lock(&eventfs_mutex); - /* If ei->is_freed, then the event itself may be too */ - if (!ei->is_freed) - r = entry->callback(name, &mode, &cdata, &fops); - else - r = -1; + /* If ei->is_freed then just bail here, nothing more to do */ + if (ei->is_freed) { + mutex_unlock(&eventfs_mutex); + goto out; + } + r = entry->callback(name, &mode, &cdata, &fops); mutex_unlock(&eventfs_mutex); if (r <= 0) continue; From patchwork Thu Jan 4 21:57:13 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Steven Rostedt X-Patchwork-Id: 13511587 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 111932C854; Thu, 4 Jan 2024 21:59:41 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id AAC44C433C7; Thu, 4 Jan 2024 21:59:41 +0000 (UTC) Received: from rostedt by gandalf with local (Exim 4.97) (envelope-from ) id 1rLVlg-00000000vgh-1JSa; Thu, 04 Jan 2024 17:00:48 -0500 Message-ID: <20240104220048.172295263@goodmis.org> User-Agent: quilt/0.67 Date: Thu, 04 Jan 2024 16:57:13 -0500 From: Steven Rostedt To: linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org Cc: Masami Hiramatsu , Mark Rutland , Mathieu Desnoyers , Andrew Morton , Linus Torvalds , Al Viro , Christian Brauner , linux-fsdevel@vger.kernel.org, Greg Kroah-Hartman Subject: [PATCH 2/4] eventfs: Do ctx->pos update for all iterations in eventfs_iterate() References: <20240104215711.924088454@goodmis.org> Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 From: "Steven Rostedt (Google)" The ctx->pos was only updated when it added an entry, but the "skip to current pos" check (c--) happened for every loop regardless of if the entry was added or not. This inconsistency caused readdir to be incorrect. It was due to: for (i = 0; i < ei->nr_entries; i++) { if (c > 0) { c--; continue; } mutex_lock(&eventfs_mutex); /* If ei->is_freed then just bail here, nothing more to do */ if (ei->is_freed) { mutex_unlock(&eventfs_mutex); goto out; } r = entry->callback(name, &mode, &cdata, &fops); mutex_unlock(&eventfs_mutex); [..] ctx->pos++; } But this can cause the iterator to return a file that was already read. That's because of the way the callback() works. Some events may not have all files, and the callback can return 0 to tell eventfs to skip the file for this directory. for instance, we have: # ls /sys/kernel/tracing/events/ftrace/function format hist hist_debug id inject and # ls /sys/kernel/tracing/events/sched/sched_switch/ enable filter format hist hist_debug id inject trigger Where the function directory is missing "enable", "filter" and "trigger". That's because the callback() for events has: static int event_callback(const char *name, umode_t *mode, void **data, const struct file_operations **fops) { struct trace_event_file *file = *data; struct trace_event_call *call = file->event_call; [..] /* * Only event directories that can be enabled should have * triggers or filters, with the exception of the "print" * event that can have a "trigger" file. */ if (!(call->flags & TRACE_EVENT_FL_IGNORE_ENABLE)) { if (call->class->reg && strcmp(name, "enable") == 0) { *mode = TRACE_MODE_WRITE; *fops = &ftrace_enable_fops; return 1; } if (strcmp(name, "filter") == 0) { *mode = TRACE_MODE_WRITE; *fops = &ftrace_event_filter_fops; return 1; } } if (!(call->flags & TRACE_EVENT_FL_IGNORE_ENABLE) || strcmp(trace_event_name(call), "print") == 0) { if (strcmp(name, "trigger") == 0) { *mode = TRACE_MODE_WRITE; *fops = &event_trigger_fops; return 1; } } [..] return 0; } Where the function event has the TRACE_EVENT_FL_IGNORE_ENABLE set. This means that the entries array elements for "enable", "filter" and "trigger" when called on the function event will have the callback return 0 and not 1, to tell eventfs to skip these files for it. Because the "skip to current ctx->pos" check happened for all entries, but the ctx->pos++ only happened to entries that exist, it would confuse the reading of a directory. Which would cause: # ls /sys/kernel/tracing/events/ftrace/function/ format hist hist hist_debug hist_debug id inject inject The missing "enable", "filter" and "trigger" caused ls to show "hist", "hist_debug" and "inject" twice. Update the ctx->pos for every iteration to keep its update and the "skip" update consistent. This also means that on error, the ctx->pos needs to be decremented if it was incremented without adding something. Link: https://lore.kernel.org/all/20240104150500.38b15a62@gandalf.local.home/ Fixes: 493ec81a8fb8e ("eventfs: Stop using dcache_readdir() for getdents()") Signed-off-by: Steven Rostedt (Google) --- fs/tracefs/event_inode.c | 21 ++++++++++++++------- 1 file changed, 14 insertions(+), 7 deletions(-) diff --git a/fs/tracefs/event_inode.c b/fs/tracefs/event_inode.c index 0aca6910efb3..c73fb1f7ddbc 100644 --- a/fs/tracefs/event_inode.c +++ b/fs/tracefs/event_inode.c @@ -760,6 +760,8 @@ static int eventfs_iterate(struct file *file, struct dir_context *ctx) continue; } + ctx->pos++; + if (ei_child->is_freed) continue; @@ -767,13 +769,12 @@ static int eventfs_iterate(struct file *file, struct dir_context *ctx) dentry = create_dir_dentry(ei, ei_child, ei_dentry); if (!dentry) - goto out; + goto out_dec; ino = dentry->d_inode->i_ino; dput(dentry); if (!dir_emit(ctx, name, strlen(name), ino, DT_DIR)) - goto out; - ctx->pos++; + goto out_dec; } for (i = 0; i < ei->nr_entries; i++) { @@ -784,6 +785,8 @@ static int eventfs_iterate(struct file *file, struct dir_context *ctx) continue; } + ctx->pos++; + entry = &ei->entries[i]; name = entry->name; @@ -791,7 +794,7 @@ static int eventfs_iterate(struct file *file, struct dir_context *ctx) /* If ei->is_freed then just bail here, nothing more to do */ if (ei->is_freed) { mutex_unlock(&eventfs_mutex); - goto out; + goto out_dec; } r = entry->callback(name, &mode, &cdata, &fops); mutex_unlock(&eventfs_mutex); @@ -800,19 +803,23 @@ static int eventfs_iterate(struct file *file, struct dir_context *ctx) dentry = create_file_dentry(ei, i, ei_dentry, name, mode, cdata, fops); if (!dentry) - goto out; + goto out_dec; ino = dentry->d_inode->i_ino; dput(dentry); if (!dir_emit(ctx, name, strlen(name), ino, DT_REG)) - goto out; - ctx->pos++; + goto out_dec; } ret = 1; out: srcu_read_unlock(&eventfs_srcu, idx); return ret; + + out_dec: + /* Incremented ctx->pos without adding something, reset it */ + ctx->pos--; + goto out; } /** From patchwork Thu Jan 4 21:57:14 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Steven Rostedt X-Patchwork-Id: 13511590 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 3B7272C863; Thu, 4 Jan 2024 21:59:41 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id C6B59C433CC; Thu, 4 Jan 2024 21:59:41 +0000 (UTC) Received: from rostedt by gandalf with local (Exim 4.97) (envelope-from ) id 1rLVlg-00000000vhD-1zwl; Thu, 04 Jan 2024 17:00:48 -0500 Message-ID: <20240104220048.333115095@goodmis.org> User-Agent: quilt/0.67 Date: Thu, 04 Jan 2024 16:57:14 -0500 From: Steven Rostedt To: linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org Cc: Masami Hiramatsu , Mark Rutland , Mathieu Desnoyers , Andrew Morton , Linus Torvalds , Al Viro , Christian Brauner , linux-fsdevel@vger.kernel.org, Greg Kroah-Hartman Subject: [PATCH 3/4] eventfs: Read ei->entries before ei->children in eventfs_iterate() References: <20240104215711.924088454@goodmis.org> Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 From: "Steven Rostedt (Google)" In order to apply a shortcut to skip over the current ctx->pos immediately, by using the ei->entries array, the reading of that array should be first. Moving the array reading before the linked list reading will make the shortcut change diff nicer to read. Link: https://lore.kernel.org/all/CAHk-=wiKwDUDv3+jCsv-uacDcHDVTYsXtBR9=6sGM5mqX+DhOg@mail.gmail.com/ Signed-off-by: Steven Rostedt (Google) --- fs/tracefs/event_inode.c | 46 ++++++++++++++++++++-------------------- 1 file changed, 23 insertions(+), 23 deletions(-) diff --git a/fs/tracefs/event_inode.c b/fs/tracefs/event_inode.c index c73fb1f7ddbc..a1934e0eea3b 100644 --- a/fs/tracefs/event_inode.c +++ b/fs/tracefs/event_inode.c @@ -752,8 +752,8 @@ static int eventfs_iterate(struct file *file, struct dir_context *ctx) * Need to create the dentries and inodes to have a consistent * inode number. */ - list_for_each_entry_srcu(ei_child, &ei->children, list, - srcu_read_lock_held(&eventfs_srcu)) { + for (i = 0; i < ei->nr_entries; i++) { + void *cdata = ei->data; if (c > 0) { c--; @@ -762,23 +762,32 @@ static int eventfs_iterate(struct file *file, struct dir_context *ctx) ctx->pos++; - if (ei_child->is_freed) - continue; + entry = &ei->entries[i]; + name = entry->name; - name = ei_child->name; + mutex_lock(&eventfs_mutex); + /* If ei->is_freed then just bail here, nothing more to do */ + if (ei->is_freed) { + mutex_unlock(&eventfs_mutex); + goto out_dec; + } + r = entry->callback(name, &mode, &cdata, &fops); + mutex_unlock(&eventfs_mutex); + if (r <= 0) + continue; - dentry = create_dir_dentry(ei, ei_child, ei_dentry); + dentry = create_file_dentry(ei, i, ei_dentry, name, mode, cdata, fops); if (!dentry) goto out_dec; ino = dentry->d_inode->i_ino; dput(dentry); - if (!dir_emit(ctx, name, strlen(name), ino, DT_DIR)) + if (!dir_emit(ctx, name, strlen(name), ino, DT_REG)) goto out_dec; } - for (i = 0; i < ei->nr_entries; i++) { - void *cdata = ei->data; + list_for_each_entry_srcu(ei_child, &ei->children, list, + srcu_read_lock_held(&eventfs_srcu)) { if (c > 0) { c--; @@ -787,27 +796,18 @@ static int eventfs_iterate(struct file *file, struct dir_context *ctx) ctx->pos++; - entry = &ei->entries[i]; - name = entry->name; - - mutex_lock(&eventfs_mutex); - /* If ei->is_freed then just bail here, nothing more to do */ - if (ei->is_freed) { - mutex_unlock(&eventfs_mutex); - goto out_dec; - } - r = entry->callback(name, &mode, &cdata, &fops); - mutex_unlock(&eventfs_mutex); - if (r <= 0) + if (ei_child->is_freed) continue; - dentry = create_file_dentry(ei, i, ei_dentry, name, mode, cdata, fops); + name = ei_child->name; + + dentry = create_dir_dentry(ei, ei_child, ei_dentry); if (!dentry) goto out_dec; ino = dentry->d_inode->i_ino; dput(dentry); - if (!dir_emit(ctx, name, strlen(name), ino, DT_REG)) + if (!dir_emit(ctx, name, strlen(name), ino, DT_DIR)) goto out_dec; } ret = 1; From patchwork Thu Jan 4 21:57:15 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Steven Rostedt X-Patchwork-Id: 13511588 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 37B932C861; Thu, 4 Jan 2024 21:59:42 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id D1CB9C43395; Thu, 4 Jan 2024 21:59:41 +0000 (UTC) Received: from rostedt by gandalf with local (Exim 4.97) (envelope-from ) id 1rLVlg-00000000vhh-2eTY; Thu, 04 Jan 2024 17:00:48 -0500 Message-ID: <20240104220048.494956957@goodmis.org> User-Agent: quilt/0.67 Date: Thu, 04 Jan 2024 16:57:15 -0500 From: Steven Rostedt To: linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org Cc: Masami Hiramatsu , Mark Rutland , Mathieu Desnoyers , Andrew Morton , Linus Torvalds , Al Viro , Christian Brauner , linux-fsdevel@vger.kernel.org, Greg Kroah-Hartman Subject: [PATCH 4/4] eventfs: Shortcut eventfs_iterate() by skipping entries already read References: <20240104215711.924088454@goodmis.org> Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 From: "Steven Rostedt (Google)" As the ei->entries array is fixed for the duration of the eventfs_inode, it can be used to skip over already read entries in eventfs_iterate(). That is, if ctx->pos is greater than zero, there's no reason in doing the loop across the ei->entries array for the entries less than ctx->pos. Instead, start the lookup of the entries at the current ctx->pos. Link: https://lore.kernel.org/all/CAHk-=wiKwDUDv3+jCsv-uacDcHDVTYsXtBR9=6sGM5mqX+DhOg@mail.gmail.com/ Suggested-by: Linus Torvalds Signed-off-by: Steven Rostedt (Google) --- fs/tracefs/event_inode.c | 23 ++++++++++------------- 1 file changed, 10 insertions(+), 13 deletions(-) diff --git a/fs/tracefs/event_inode.c b/fs/tracefs/event_inode.c index a1934e0eea3b..fdff53d5a1f8 100644 --- a/fs/tracefs/event_inode.c +++ b/fs/tracefs/event_inode.c @@ -746,21 +746,15 @@ static int eventfs_iterate(struct file *file, struct dir_context *ctx) if (!ei || !ei_dentry) goto out; - ret = 0; - /* * Need to create the dentries and inodes to have a consistent * inode number. */ - for (i = 0; i < ei->nr_entries; i++) { - void *cdata = ei->data; - - if (c > 0) { - c--; - continue; - } + ret = 0; - ctx->pos++; + /* Start at 'c' to jump over already read entries */ + for (i = c; i < ei->nr_entries; i++, ctx->pos++) { + void *cdata = ei->data; entry = &ei->entries[i]; name = entry->name; @@ -769,7 +763,7 @@ static int eventfs_iterate(struct file *file, struct dir_context *ctx) /* If ei->is_freed then just bail here, nothing more to do */ if (ei->is_freed) { mutex_unlock(&eventfs_mutex); - goto out_dec; + goto out; } r = entry->callback(name, &mode, &cdata, &fops); mutex_unlock(&eventfs_mutex); @@ -778,14 +772,17 @@ static int eventfs_iterate(struct file *file, struct dir_context *ctx) dentry = create_file_dentry(ei, i, ei_dentry, name, mode, cdata, fops); if (!dentry) - goto out_dec; + goto out; ino = dentry->d_inode->i_ino; dput(dentry); if (!dir_emit(ctx, name, strlen(name), ino, DT_REG)) - goto out_dec; + goto out; } + /* Subtract the skipped entries above */ + c -= min((unsigned int)c, (unsigned int)ei->nr_entries); + list_for_each_entry_srcu(ei_child, &ei->children, list, srcu_read_lock_held(&eventfs_srcu)) {