From mboxrd@z Thu Jan 1 00:00:00 1970 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 BD6931487D5; Thu, 30 Jan 2025 14:16:49 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1738246609; cv=none; b=W1PYFG6lQhWqq0hd/K0lWFtXltY0eFWRzVJhRw5zsBcysdjSixDgty8jIITL6aMPZT30VB5rYtT6X81ZlNaff5eYh7LsaAXrdjpNAq8NbhXyM3Jq9ALSFwdYdAx4hxHWjtqBG2UKt4my/roH6O734Z2Jdtxoo9oC/Vc6LfbMKT8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1738246609; c=relaxed/simple; bh=fqnslBpRAu64wEEVOQEfAcE+ahmrSwf4tf/mpbfyQzI=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=SgXGxDr0U0pXxC2Q/7gsZSUtxpAyD0IFiy/8OzJC+5sJbSF8PlO+aZBcu7V+2SIJ+G8E+A67O52FS3BJfgGUW2is6b6M8Kv/LxBFxNKEFuLn/kGzY4EMJ/po/xtY/KHkSwTRzAevQuhEfzMZKyWyfaEba/s4bS/5uk/TgUB05Jw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=f7ZRQAJW; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="f7ZRQAJW" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3F926C4CED2; Thu, 30 Jan 2025 14:16:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1738246609; bh=fqnslBpRAu64wEEVOQEfAcE+ahmrSwf4tf/mpbfyQzI=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=f7ZRQAJWJ1iQwoDDxlG9LBfGhfDqcrk6V5wKAK0FcSgNFdJfOfCnG/hQd9oAgeJsX Ro9ya26z1Q2qzmJYo4LVawhLzN2yQTDUHQDDqXbOhWaP4Ahs8J12u6Ca21JpSr4SxV 2oZ1FFBvnFc22WcN40i9FKt8zCVR932Fd33mG5AY= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Chuck Lever , Christian Brauner Subject: [PATCH 6.6 24/43] libfs: Use d_children list to iterate simple_offset directories Date: Thu, 30 Jan 2025 14:59:31 +0100 Message-ID: <20250130133459.876402442@linuxfoundation.org> X-Mailer: git-send-email 2.48.1 In-Reply-To: <20250130133458.903274626@linuxfoundation.org> References: <20250130133458.903274626@linuxfoundation.org> User-Agent: quilt/0.68 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.6-stable review patch. If anyone has any objections, please let me know. ------------------ From: Chuck Lever [ Upstream commit b9b588f22a0c049a14885399e27625635ae6ef91 ] The mtree mechanism has been effective at creating directory offsets that are stable over multiple opendir instances. However, it has not been able to handle the subtleties of renames that are concurrent with readdir. Instead of using the mtree to emit entries in the order of their offset values, use it only to map incoming ctx->pos to a starting entry. Then use the directory's d_children list, which is already maintained properly by the dcache, to find the next child to emit. One of the sneaky things about this is that when the mtree-allocated offset value wraps (which is very rare), looking up ctx->pos++ is not going to find the next entry; it will return NULL. Instead, by following the d_children list, the offset values can appear in any order but all of the entries in the directory will be visited eventually. Note also that the readdir() is guaranteed to reach the tail of this list. Entries are added only at the head of d_children, and readdir walks from its current position in that list towards its tail. Signed-off-by: Chuck Lever Link: https://lore.kernel.org/r/20241228175522.1854234-6-cel@kernel.org Signed-off-by: Christian Brauner [ cel: adjusted to apply to origin/linux-6.6.y ] Signed-off-by: Chuck Lever Signed-off-by: Greg Kroah-Hartman --- fs/libfs.c | 84 ++++++++++++++++++++++++++++++++++++++++++------------------- 1 file changed, 59 insertions(+), 25 deletions(-) --- a/fs/libfs.c +++ b/fs/libfs.c @@ -241,12 +241,13 @@ EXPORT_SYMBOL(simple_dir_inode_operation /* simple_offset_add() never assigns these to a dentry */ enum { + DIR_OFFSET_FIRST = 2, /* Find first real entry */ DIR_OFFSET_EOD = S32_MAX, }; /* simple_offset_add() allocation range */ enum { - DIR_OFFSET_MIN = 2, + DIR_OFFSET_MIN = DIR_OFFSET_FIRST + 1, DIR_OFFSET_MAX = DIR_OFFSET_EOD - 1, }; @@ -452,51 +453,84 @@ static loff_t offset_dir_llseek(struct f return vfs_setpos(file, offset, U32_MAX); } -static struct dentry *offset_find_next(struct offset_ctx *octx, loff_t offset) +static struct dentry *find_positive_dentry(struct dentry *parent, + struct dentry *dentry, + bool next) +{ + struct dentry *found = NULL; + + spin_lock(&parent->d_lock); + if (next) + dentry = list_next_entry(dentry, d_child); + else if (!dentry) + dentry = list_first_entry_or_null(&parent->d_subdirs, + struct dentry, d_child); + for (; dentry && !list_entry_is_head(dentry, &parent->d_subdirs, d_child); + dentry = list_next_entry(dentry, d_child)) { + if (!simple_positive(dentry)) + continue; + spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED); + if (simple_positive(dentry)) + found = dget_dlock(dentry); + spin_unlock(&dentry->d_lock); + if (likely(found)) + break; + } + spin_unlock(&parent->d_lock); + return found; +} + +static noinline_for_stack struct dentry * +offset_dir_lookup(struct dentry *parent, loff_t offset) { + struct inode *inode = d_inode(parent); + struct offset_ctx *octx = inode->i_op->get_offset_ctx(inode); struct dentry *child, *found = NULL; + XA_STATE(xas, &octx->xa, offset); - rcu_read_lock(); - child = xas_next_entry(&xas, DIR_OFFSET_MAX); - if (!child) - goto out; - spin_lock(&child->d_lock); - if (simple_positive(child)) - found = dget_dlock(child); - spin_unlock(&child->d_lock); -out: - rcu_read_unlock(); + if (offset == DIR_OFFSET_FIRST) + found = find_positive_dentry(parent, NULL, false); + else { + rcu_read_lock(); + child = xas_next_entry(&xas, DIR_OFFSET_MAX); + found = find_positive_dentry(parent, child, false); + rcu_read_unlock(); + } return found; } static bool offset_dir_emit(struct dir_context *ctx, struct dentry *dentry) { - u32 offset = dentry2offset(dentry); struct inode *inode = d_inode(dentry); - return ctx->actor(ctx, dentry->d_name.name, dentry->d_name.len, offset, - inode->i_ino, fs_umode_to_dtype(inode->i_mode)); + return dir_emit(ctx, dentry->d_name.name, dentry->d_name.len, + inode->i_ino, fs_umode_to_dtype(inode->i_mode)); } -static void offset_iterate_dir(struct inode *inode, struct dir_context *ctx) +static void offset_iterate_dir(struct file *file, struct dir_context *ctx) { - struct offset_ctx *octx = inode->i_op->get_offset_ctx(inode); + struct dentry *dir = file->f_path.dentry; struct dentry *dentry; + dentry = offset_dir_lookup(dir, ctx->pos); + if (!dentry) + goto out_eod; while (true) { - dentry = offset_find_next(octx, ctx->pos); - if (!dentry) - goto out_eod; + struct dentry *next; - if (!offset_dir_emit(ctx, dentry)) { - dput(dentry); + ctx->pos = dentry2offset(dentry); + if (!offset_dir_emit(ctx, dentry)) break; - } - ctx->pos = dentry2offset(dentry) + 1; + next = find_positive_dentry(dir, dentry, true); dput(dentry); + + if (!next) + goto out_eod; + dentry = next; } + dput(dentry); return; out_eod: @@ -535,7 +569,7 @@ static int offset_readdir(struct file *f if (!dir_emit_dots(file, ctx)) return 0; if (ctx->pos != DIR_OFFSET_EOD) - offset_iterate_dir(d_inode(dir), ctx); + offset_iterate_dir(file, ctx); return 0; }