From patchwork Fri Nov 15 15:30:29 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Josef Bacik X-Patchwork-Id: 13876500 Received: from mail-yb1-f178.google.com (mail-yb1-f178.google.com [209.85.219.178]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 7FC701F4295 for ; Fri, 15 Nov 2024 15:31:55 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.219.178 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1731684717; cv=none; b=VCjb5dQyPsesdU4gkkGqvoGhvyjwuGqAVGf5RgR2MoM1dZaSo9r0wUcNSLuWSPaEYgSsJuUG96T+6PB9dEyRUwBEspqoI5/pKQIP5sWfVP/8VaU17Z9lOtn0V2Dte9DnY93pvhvLPMuq9fU2C1+uSeLnWEQM8OR145J4awfCyh0= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1731684717; c=relaxed/simple; bh=32HChrQf54ppyFpL+uRbV0WQCoSZt7JFC7d0t8FH4FM=; h=From:To:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=btulAgVD7cmF0uq0/uqnEolFA8mNj5+CYPjB+cqwolmKyTN/PAgyQJ/h+vAWKpLL2SgdyFtN9J9Ck2WDaYw43UgXjKG2n7kP1vwbsXcMowPQajuqIbe5sxGbLddb3sNtkIscpe45i3AuGz1a0vrmy324yOd0URjsfLnNsZ+lUjY= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=toxicpanda.com; spf=none smtp.mailfrom=toxicpanda.com; dkim=pass (2048-bit key) header.d=toxicpanda-com.20230601.gappssmtp.com header.i=@toxicpanda-com.20230601.gappssmtp.com header.b=jA61qXD0; arc=none smtp.client-ip=209.85.219.178 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=toxicpanda.com Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=toxicpanda.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=toxicpanda-com.20230601.gappssmtp.com header.i=@toxicpanda-com.20230601.gappssmtp.com header.b="jA61qXD0" Received: by mail-yb1-f178.google.com with SMTP id 3f1490d57ef6-e380e038749so1810565276.3 for ; Fri, 15 Nov 2024 07:31:55 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=toxicpanda-com.20230601.gappssmtp.com; s=20230601; t=1731684714; x=1732289514; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:to:from:from:to:cc:subject:date:message-id :reply-to; bh=3KCTaRjNmkxmxaKf/dEMrgpxbgs8A3iRugI4cag6Bm4=; b=jA61qXD0D+5s1K3oXaOlt3fiKxBu4Z1olSsgdJsIA0G38KJ8AqkvsFDcLzgAlrJZ52 Hn24JTZTb1L2XNUb5XqEBTOzJ98S98UZYMp5rc9YC71wP6Ffo3/EZ34kLqFby2MNPi6Y Ofgo+NSfyVe67MVsvzVOqQZjMa1t16WDshS1PMB0R1f8rnItl1WpQQarS0gebZUMLrJf v8hjEm5gZYyZJoP0Wx8p3pVpjyp1dSaXDuaHTxo2lQULdK2V30Zi+ygWrCtFBEmZ2trn pSsRhAIGONoFL8/ueM9bhjgi3Ms1Ikaqjkqi/WzdLBk+oZOs4PWPkRgd3XbpBbV3R1/h Ziww== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1731684714; x=1732289514; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=3KCTaRjNmkxmxaKf/dEMrgpxbgs8A3iRugI4cag6Bm4=; b=TXwn1hGjqOklegqDsecA4bI4uM8tsg29Eiy57LXe9DD5ZID0p69KWKJKen1M56j3Sm F1CBdGwXlWdwHse7NmHhSQdnpN1lBBvmxB9bPUAT0e5DbLykUdXyFCr9xkVSFONI1+0I Q2s7T2Qm66AF1OyPdJng9V3eGwqCzVS0SZllKjPiTTjJaWqTq9tlt70GW4aVWA1l4JTg Nn0LgsQFVKGP2fg5xLMavIFfsrnAPPeF1Vhak9eBTznWcqEHc/lTNjNhlD7a2ns3lD94 Mx6aKMfbOtFiKAmEjRCd9kb9+8YRf4whUaX8L9/Zy3xtky5uvBFcu+TZxjWwmUt5/9DI FICw== X-Forwarded-Encrypted: i=1; AJvYcCVyUo2AXO1zrobVr1YL6va2vcg6CwlJMvr826GdbT7gGcdm4ERtfw6b00TNW7gF1MKCwcNbog4nQfcswQ==@vger.kernel.org X-Gm-Message-State: AOJu0YzVnCaOYsC4T2J33KEkDYjF3GkUkDNecejTUF+vrRRDCaKa3O2B hHQBGItEj9QclzS8Mb0lW4d2N2oogqEKao1Waz1HGs090aAhuGMqCBBg2HhCgGE= X-Google-Smtp-Source: AGHT+IFmVYcZJStgSp9a9E1dsOyyT4rBH0daYbq6mRod+diiaSsdzS2Ed6cQkqbS64804RotiUDKFQ== X-Received: by 2002:a05:690c:9:b0:6e2:a129:1623 with SMTP id 00721157ae682-6ee55c69ee9mr29748387b3.38.1731684714337; Fri, 15 Nov 2024 07:31:54 -0800 (PST) Received: from localhost (syn-076-182-020-124.res.spectrum.com. [76.182.20.124]) by smtp.gmail.com with ESMTPSA id 00721157ae682-6ee4444ccdfsm7704207b3.120.2024.11.15.07.31.53 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 15 Nov 2024 07:31:53 -0800 (PST) From: Josef Bacik To: kernel-team@fb.com, linux-fsdevel@vger.kernel.org, jack@suse.cz, amir73il@gmail.com, brauner@kernel.org, torvalds@linux-foundation.org, viro@zeniv.linux.org.uk, linux-xfs@vger.kernel.org, linux-btrfs@vger.kernel.org, linux-mm@kvack.org, linux-ext4@vger.kernel.org Subject: [PATCH v8 16/19] fsnotify: generate pre-content permission event on page fault Date: Fri, 15 Nov 2024 10:30:29 -0500 Message-ID: X-Mailer: git-send-email 2.43.0 In-Reply-To: References: Precedence: bulk X-Mailing-List: linux-btrfs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 FS_PRE_ACCESS or FS_PRE_MODIFY will be generated on page fault depending on the faulting method. This pre-content event is meant to be used by hierarchical storage managers that want to fill in the file content on first read access. Export a simple helper that file systems that have their own ->fault() will use, and have a more complicated helper to be do fancy things with in filemap_fault. Signed-off-by: Josef Bacik --- include/linux/mm.h | 1 + mm/filemap.c | 78 ++++++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 79 insertions(+) diff --git a/include/linux/mm.h b/include/linux/mm.h index 01c5e7a4489f..90155ef8599a 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -3406,6 +3406,7 @@ extern vm_fault_t filemap_fault(struct vm_fault *vmf); extern vm_fault_t filemap_map_pages(struct vm_fault *vmf, pgoff_t start_pgoff, pgoff_t end_pgoff); extern vm_fault_t filemap_page_mkwrite(struct vm_fault *vmf); +extern vm_fault_t filemap_fsnotify_fault(struct vm_fault *vmf); extern unsigned long stack_guard_gap; /* Generic expand stack which grows the stack according to GROWS{UP,DOWN} */ diff --git a/mm/filemap.c b/mm/filemap.c index 68ea596f6905..0bf7d645dec5 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -47,6 +47,7 @@ #include #include #include +#include #include #include #include "internal.h" @@ -3289,6 +3290,52 @@ static vm_fault_t filemap_fault_recheck_pte_none(struct vm_fault *vmf) return ret; } +/** + * filemap_fsnotify_fault - maybe emit a pre-content event. + * @vmf: struct vm_fault containing details of the fault. + * @folio: the folio we're faulting in. + * + * If we have a pre-content watch on this file we will emit an event for this + * range. If we return anything the fault caller should return immediately, we + * will return VM_FAULT_RETRY if we had to emit an event, which will trigger the + * fault again and then the fault handler will run the second time through. + * + * This is meant to be called with the folio that we will be filling in to make + * sure the event is emitted for the correct range. + * + * Return: a bitwise-OR of %VM_FAULT_ codes, 0 if nothing happened. + */ +vm_fault_t filemap_fsnotify_fault(struct vm_fault *vmf) +{ + struct file *fpin = NULL; + int mask = (vmf->flags & FAULT_FLAG_WRITE) ? MAY_WRITE : MAY_ACCESS; + loff_t pos = vmf->pgoff >> PAGE_SHIFT; + size_t count = PAGE_SIZE; + vm_fault_t ret; + + /* + * We already did this and now we're retrying with everything locked, + * don't emit the event and continue. + */ + if (vmf->flags & FAULT_FLAG_TRIED) + return 0; + + /* No watches, we're done. */ + if (!fsnotify_file_has_pre_content_watches(vmf->vma->vm_file)) + return 0; + + fpin = maybe_unlock_mmap_for_io(vmf, fpin); + if (!fpin) + return VM_FAULT_SIGBUS; + + ret = fsnotify_file_area_perm(fpin, mask, &pos, count); + fput(fpin); + if (ret) + return VM_FAULT_SIGBUS; + return VM_FAULT_RETRY; +} +EXPORT_SYMBOL_GPL(filemap_fsnotify_fault); + /** * filemap_fault - read in file data for page fault handling * @vmf: struct vm_fault containing details of the fault @@ -3392,6 +3439,37 @@ vm_fault_t filemap_fault(struct vm_fault *vmf) * or because readahead was otherwise unable to retrieve it. */ if (unlikely(!folio_test_uptodate(folio))) { + /* + * If this is a precontent file we have can now emit an event to + * try and populate the folio. + */ + if (!(vmf->flags & FAULT_FLAG_TRIED) && + fsnotify_file_has_pre_content_watches(file)) { + loff_t pos = folio_pos(folio); + size_t count = folio_size(folio); + + /* We're NOWAIT, we have to retry. */ + if (vmf->flags & FAULT_FLAG_RETRY_NOWAIT) { + folio_unlock(folio); + goto out_retry; + } + + if (mapping_locked) + filemap_invalidate_unlock_shared(mapping); + mapping_locked = false; + + folio_unlock(folio); + fpin = maybe_unlock_mmap_for_io(vmf, fpin); + if (!fpin) + goto out_retry; + + error = fsnotify_file_area_perm(fpin, MAY_ACCESS, &pos, + count); + if (error) + ret = VM_FAULT_SIGBUS; + goto out_retry; + } + /* * If the invalidate lock is not held, the folio was in cache * and uptodate and now it is not. Strange but possible since we