From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from verein.lst.de (verein.lst.de [213.95.11.211]) (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 E3D58431E43; Mon, 20 Jul 2026 14:41:46 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=213.95.11.211 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784558511; cv=none; b=G0H84env9J1frbvT2IfWZH4mGbvEejiuBjXxvPy78ieAl3l2ddgLP4ZPISEYeDb7zR9M467lcSv+qkhf8TkvBV+JEgHO6hcErz26uTit6W8g+O+toyNibfPyuHoghPelUqHwmW++dFCR0E6qzUQlKU5Z01gPNHee5vsjBKukxGo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784558511; c=relaxed/simple; bh=oJfujzCtMKrxNILgudZSHedCBI4VmL+Wifsa/DxjPZo=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=h6UukREWt+KWu3CDW/JuDkB4Vj2B7/1abWc3+KB0lLMRHxY8CtPqXa4sgR8WnVHxbxJ4kQt1nhdMdL5/5Cu3w6kfQOakDH+bB9+mpsUh2cEYZnDeiSnGy8KmxiYCj+g5Gqj5YplqE1Rfb43bAz1O0IPDYSCmadtqnGsczOR3pr4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=lst.de; spf=pass smtp.mailfrom=lst.de; arc=none smtp.client-ip=213.95.11.211 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=lst.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=lst.de Received: by verein.lst.de (Postfix, from userid 2407) id EEEC468C4E; Mon, 20 Jul 2026 16:41:41 +0200 (CEST) Date: Mon, 20 Jul 2026 16:41:41 +0200 From: Christoph Hellwig To: Mark Brown Cc: Andrew Morton , Christoph Hellwig , Linux Kernel Mailing List , Linux Next Mailing List , Matthew Brost , Hugh Dickins , Baolin Wang , linux-mm@kvack.org Subject: Re: linux-next: manual merge of the mm-unstable tree with the drm-misc-fixes tree Message-ID: <20260720144141.GA16699@lst.de> References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.17 (2007-11-01) On Mon, Jul 20, 2026 at 02:31:04PM +0100, Mark Brown wrote: > Hi all, > > Today's linux-next merge of the mm-unstable tree got a conflict in: > > drivers/gpu/drm/ttm/ttm_backup.c > > between commit: > > a3fdf74ffa596 ("drm/ttm/pool: back up at native page order") > > from the drm-misc-fixes tree and commit: > > c6bfdcf16f131 ("shmem: provide a shmem_write_folio wrapper") > > from the mm-unstable tree. > > I fixed it up (see below) and can carry the fix as necessary. This > is now fixed as far as linux-next is concerned, but any non trivial > conflicts should be mentioned to your upstream maintainer when your tree > is submitted for merging. You may also want to consider cooperating > with the maintainer of the conflicting tree to minimise any particularly > complex conflicts. Much of the code here really should sit in shmem.c instead of having random drivers/subsystems poke into the internals of shmem mappings and folios. But I feel like a broken record for saying that again and again without any action :( > > diff --combined drivers/gpu/drm/ttm/ttm_backup.c > index 3c067aadc52de,c5b813a563e7f..0000000000000 > --- a/drivers/gpu/drm/ttm/ttm_backup.c > +++ b/drivers/gpu/drm/ttm/ttm_backup.c > @@@ -6,10 -6,9 +6,10 @@@ > #include > > #include > -#include > #include > > +#include "ttm_pool_internal.h" > + > /* > * Need to map shmem indices to handle since a handle value > * of 0 means error, following the swp_entry_t convention. > @@@ -69,23 -68,17 +69,23 @@@ int ttm_backup_copy_page(struct file *b > } > > /** > - * ttm_backup_backup_page() - Backup a page > + * ttm_backup_backup_folio() - Backup a folio > * @backup: The struct backup pointer to use. > - * @page: The page to back up. > - * @writeback: Whether to perform immediate writeback of the page. > + * @folio: The folio to back up. > + * @order: The allocation order of @folio. Since TTM allocates higher-order > + * pages without __GFP_COMP, folio_nr_pages(@folio) would always > + * return 1; the caller must pass the true order explicitly. > + * @writeback: Whether to perform immediate writeback of the folio's pages. > * This may have performance implications. > - * @idx: A unique integer for each page and each struct backup. > + * @idx: A unique integer for the first page of the folio and each struct backup. > * This allows the backup implementation to avoid managing > * its address space separately. > - * @page_gfp: The gfp value used when the page was allocated. > - * This is used for accounting purposes. > + * @folio_gfp: The gfp value used when the folio was allocated. > + * Currently unused. > * @alloc_gfp: The gfp to be used when allocating memory. > + * @nr_pages_backed: Output. On a successful return, set to the number of > + * pages actually backed up, which may be less than (1 << @order) > + * if an -ENOMEM was encountered mid-folio. > * > * Context: If called from reclaim context, the caller needs to > * assert that the shrinker gfp has __GFP_FS set, to avoid > @@@ -94,87 -87,53 +94,87 @@@ > * that the shrinker gfp has __GFP_IO set, since without it, > * we're not allowed to start backup IO. > * > - * Return: A handle on success. Negative error code on failure. > - * > - * Note: This function could be extended to back up a folio and > - * implementations would then split the folio internally if needed. > - * Drawback is that the caller would then have to keep track of > - * the folio size- and usage. > + * Return: A handle for the first backed-up page on success (handles for > + * subsequent pages follow sequentially). -ENOMEM if no pages could be backed > + * up. Any other negative error code if a non-ENOMEM failure occurred; in that > + * case any pages backed up so far are truncated before returning. > */ > s64 > -ttm_backup_backup_page(struct file *backup, struct page *page, > - bool writeback, pgoff_t idx, gfp_t page_gfp, > - gfp_t alloc_gfp) > +ttm_backup_backup_folio(struct file *backup, struct folio *folio, > + unsigned int order, bool writeback, pgoff_t idx, > + gfp_t folio_gfp, gfp_t alloc_gfp, > + pgoff_t *nr_pages_backed) > { > struct address_space *mapping = backup->f_mapping; > - unsigned long handle = 0; > + int nr_pages = 1 << order; > struct folio *to_folio; > - int ret; > + int ret, i; > > - to_folio = shmem_read_folio_gfp(mapping, idx, alloc_gfp); > - if (IS_ERR(to_folio)) > - return PTR_ERR(to_folio); > + *nr_pages_backed = 0; > > - folio_mark_accessed(to_folio); > - folio_lock(to_folio); > - folio_mark_dirty(to_folio); > - copy_highpage(folio_file_page(to_folio, idx), page); > - handle = ttm_backup_shmem_idx_to_handle(idx); > + for (i = 0; i < nr_pages; ) { > + int to_nr, j; > > - if (writeback && !folio_mapped(to_folio) && > - folio_clear_dirty_for_io(to_folio)) { > - folio_set_reclaim(to_folio); > - ret = shmem_write_folio(to_folio); > - if (!folio_test_writeback(to_folio)) > - folio_clear_reclaim(to_folio); > /* > - * If writeout succeeds, it unlocks the folio. errors > - * are otherwise dropped, since writeout is only best > - * effort here. > + * Only inject past the first subpage so *nr_pages_backed is > + * always > 0 here, matching a genuine mid-compound -ENOMEM > + * and driving the caller's reactive split fallback instead > + * of an early, no-progress failure. > */ > - if (ret) > + if (IS_ENABLED(CONFIG_FAULT_INJECTION) && i && > + ttm_backup_fault_inject_folio()) > + to_folio = ERR_PTR(-ENOMEM); > + else > + to_folio = shmem_read_folio_gfp(mapping, idx + i, alloc_gfp); > + if (IS_ERR(to_folio)) { > + int err = PTR_ERR(to_folio); > + > + if (err == -ENOMEM && *nr_pages_backed) > + return ttm_backup_shmem_idx_to_handle(idx); > + > + if (*nr_pages_backed) { > + shmem_truncate_range(file_inode(backup), > + (loff_t)idx << PAGE_SHIFT, > + ((loff_t)(idx + i) << PAGE_SHIFT) - 1); > + /* > + * The pages just truncated are no longer > + * backed up; don't let the caller mistake > + * them for valid handles. > + */ > + *nr_pages_backed = 0; > + } > + return err; > + } > + > + to_nr = min_t(int, nr_pages - i, > + folio_next_index(to_folio) - (idx + i)); > + > + folio_mark_accessed(to_folio); > + folio_lock(to_folio); > + folio_mark_dirty(to_folio); > + > + for (j = 0; j < to_nr; j++) > + copy_highpage(folio_file_page(to_folio, idx + i + j), > + folio_page(folio, i + j)); > + > + if (writeback && !folio_mapped(to_folio) && > + folio_clear_dirty_for_io(to_folio)) { > + folio_set_reclaim(to_folio); > ++ ret = shmem_write_folio(to_folio); > + if (!folio_test_writeback(to_folio)) > + folio_clear_reclaim(to_folio); > + if (ret == AOP_WRITEPAGE_ACTIVATE) > + folio_unlock(to_folio); > + } else { > folio_unlock(to_folio); > - } else { > - folio_unlock(to_folio); > + } > + > + folio_put(to_folio); > + i += to_nr; > + *nr_pages_backed = i; > } > > - folio_put(to_folio); > - > - return handle; > + return ttm_backup_shmem_idx_to_handle(idx); > } > > /** ---end quoted text---