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 9874B2628D for ; Sat, 9 May 2026 03:22:31 +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=1778296952; cv=none; b=CGmGQSba4fwohHki2l5xbJwx4h7NdPgCsRJ5pb089xYrrXp4duMnfRd7NbZwC/yjTiCgS6zdk2wq0jQyTVhZRK2YN4Q1kXcIB00K9QSUA3dAXIy8zzO/19g04bJnnkN6VpxnBnH/dKyPJIigGwVPpQ6mHJ15W9VI3f5sDEpLEwA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778296952; c=relaxed/simple; bh=xYC5APhpuXuJMhAQGgy1Ki95P4Mp/kkir11f7iCKv1g=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=noZnGoSmY+WzD4bTYrJwWQlMpFfgtlm+rcHnB5oBjoTUwGC8Q1JXavgYeT3XMlLg9ZHlfPeeZB3z07udlFm2okITLt/WFjKA0dsS2i1nsjcTQg1w2lpzLd6GH1hHxMxfi9fY3f1/DJQbCGlHfgHZnPep2BXfxxZDSkmnuBBUK34= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=CEWeaxX2; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="CEWeaxX2" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 4DE87C2BCB0; Sat, 9 May 2026 03:22:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1778296951; bh=xYC5APhpuXuJMhAQGgy1Ki95P4Mp/kkir11f7iCKv1g=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=CEWeaxX2XCHeZRH9MrxlcIUywJYdLdilNpZn144pv7gDqN2sS7UX7OqVV82d2NBb3 +jtIusk+3/PfDH/u0tYEkuR3223NwtKeyz//LSONozCYS8WVa/qc+9tYVy952wPPcZ YapmpCRgmMAJwqNpCRjYWpz4T+YP3c7ttpfPPGyBLb9OW0yhXwzWt1EYSKOUfQ4ecg 7vjzKGV9F8ruPrvv8nXaqPU2M6oYnQZqjBdDabX3WT0FJgPrtVMoEksOoDw6TpgiDL vVDQRaJdLRGo00Zatc82mp4CiQWHEFB2cW6jdDoOPAA3CWODEP4LX4niGg5eHKpVTi Uu3E64zdnWEaw== From: Sasha Levin To: stable@vger.kernel.org Cc: Gao Xiang , Chao Yu , Sasha Levin Subject: [PATCH 6.18.y 1/2] erofs: tidy up z_erofs_lz4_handle_overlap() Date: Fri, 8 May 2026 23:22:28 -0400 Message-ID: <20260509032229.3064816-1-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <2026050413-commute-discourse-5f47@gregkh> References: <2026050413-commute-discourse-5f47@gregkh> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Gao Xiang [ Upstream commit 9ae77198d4815c63fc8ebacc659c71d150d1e51b ] - Add some useful comments to explain inplace I/Os and decompression; - Rearrange the code to get rid of one unnecessary goto. Reviewed-by: Chao Yu Signed-off-by: Gao Xiang Stable-dep-of: 21e161de2dc6 ("erofs: fix unsigned underflow in z_erofs_lz4_handle_overlap()") Signed-off-by: Sasha Levin --- fs/erofs/decompressor.c | 85 ++++++++++++++++++++++------------------- 1 file changed, 46 insertions(+), 39 deletions(-) diff --git a/fs/erofs/decompressor.c b/fs/erofs/decompressor.c index 354762c9723f9..2f4cef67cf640 100644 --- a/fs/erofs/decompressor.c +++ b/fs/erofs/decompressor.c @@ -105,44 +105,58 @@ static int z_erofs_lz4_prepare_dstpages(struct z_erofs_decompress_req *rq, return kaddr ? 1 : 0; } -static void *z_erofs_lz4_handle_overlap(struct z_erofs_decompress_req *rq, +static void *z_erofs_lz4_handle_overlap(const struct z_erofs_decompress_req *rq, void *inpage, void *out, unsigned int *inputmargin, int *maptype, bool may_inplace) { - unsigned int oend, omargin, total, i; + unsigned int oend, omargin, cnt, i; struct page **in; - void *src, *tmp; - - if (rq->inplace_io) { - oend = rq->pageofs_out + rq->outputsize; - omargin = PAGE_ALIGN(oend) - oend; - if (rq->partial_decoding || !may_inplace || - omargin < LZ4_DECOMPRESS_INPLACE_MARGIN(rq->inputsize)) - goto docopy; + void *src; + /* + * If in-place I/O isn't used, for example, the bounce compressed cache + * can hold data for incomplete read requests. Just map the compressed + * buffer as well and decompress directly. + */ + if (!rq->inplace_io) { + if (rq->inpages <= 1) { + *maptype = 0; + return inpage; + } + kunmap_local(inpage); + src = erofs_vm_map_ram(rq->in, rq->inpages); + if (!src) + return ERR_PTR(-ENOMEM); + *maptype = 1; + return src; + } + /* + * Then, deal with in-place I/Os. The reasons why in-place I/O is useful + * are: (1) It minimizes memory footprint during the I/O submission, + * which is useful for slow storage (including network devices and + * low-end HDDs/eMMCs) but with a lot inflight I/Os; (2) If in-place + * decompression can also be applied, it will reuse the unique buffer so + * that no extra CPU D-cache is polluted with temporary compressed data + * for extreme performance. + */ + oend = rq->pageofs_out + rq->outputsize; + omargin = PAGE_ALIGN(oend) - oend; + if (!rq->partial_decoding && may_inplace && + omargin >= LZ4_DECOMPRESS_INPLACE_MARGIN(rq->inputsize)) { for (i = 0; i < rq->inpages; ++i) if (rq->out[rq->outpages - rq->inpages + i] != rq->in[i]) - goto docopy; - kunmap_local(inpage); - *maptype = 3; - return out + ((rq->outpages - rq->inpages) << PAGE_SHIFT); - } - - if (rq->inpages <= 1) { - *maptype = 0; - return inpage; + break; + if (i >= rq->inpages) { + kunmap_local(inpage); + *maptype = 3; + return out + ((rq->outpages - rq->inpages) << PAGE_SHIFT); + } } - kunmap_local(inpage); - src = erofs_vm_map_ram(rq->in, rq->inpages); - if (!src) - return ERR_PTR(-ENOMEM); - *maptype = 1; - return src; - -docopy: - /* Or copy compressed data which can be overlapped to per-CPU buffer */ - in = rq->in; + /* + * If in-place decompression can't be applied, copy compressed data that + * may potentially overlap during decompression to a per-CPU buffer. + */ src = z_erofs_get_gbuf(rq->inpages); if (!src) { DBG_BUGON(1); @@ -150,20 +164,13 @@ static void *z_erofs_lz4_handle_overlap(struct z_erofs_decompress_req *rq, return ERR_PTR(-EFAULT); } - tmp = src; - total = rq->inputsize; - while (total) { - unsigned int page_copycnt = - min_t(unsigned int, total, PAGE_SIZE - *inputmargin); - + for (i = 0, in = rq->in; i < rq->inputsize; i += cnt, ++in) { + cnt = min_t(u32, rq->inputsize - i, PAGE_SIZE - *inputmargin); if (!inpage) inpage = kmap_local_page(*in); - memcpy(tmp, inpage + *inputmargin, page_copycnt); + memcpy(src + i, inpage + *inputmargin, cnt); kunmap_local(inpage); inpage = NULL; - tmp += page_copycnt; - total -= page_copycnt; - ++in; *inputmargin = 0; } *maptype = 2; -- 2.53.0