From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp-out2.suse.de (smtp-out2.suse.de [195.135.220.29]) (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 7349E9449 for ; Thu, 9 Mar 2023 11:13:13 +0000 (UTC) Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by smtp-out2.suse.de (Postfix) with ESMTPS id BA22820038; Thu, 9 Mar 2023 11:13:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_rsa; t=1678360391; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=Gbf95vBZ5k9dAL8M3+AX1LlYXPAiH98C9Dqf/EiMlS8=; b=L4GQl+rCi7b/MlyiNCdlvP2/QHKYSvrumdcDGMrBzztwmi38bCFmnGky5OC57tE0RHNqs1 7ixmN+UDKQDs7qdXNJXp8kM4Yh6i0SgG3yx2LHagLLa6elEk0YbHrXOHaRnzB3yiNaZ15O 06yPlYNnALxdXMnr1zP8jY0WKHDijDI= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_ed25519; t=1678360391; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=Gbf95vBZ5k9dAL8M3+AX1LlYXPAiH98C9Dqf/EiMlS8=; b=RqUUZs3zze8kfxz8IeZ6c3MJNo33G7eXkX3dJBPrfXidjrYIU6s49P6pyslGajl/2z7Pgk kkgN3lTDU9B34LBw== Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by imap2.suse-dmz.suse.de (Postfix) with ESMTPS id 9F19A1391B; Thu, 9 Mar 2023 11:13:11 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id 4KlAJke/CWRiRwAAMHmgww (envelope-from ); Thu, 09 Mar 2023 11:13:11 +0000 From: Vlastimil Babka To: Andrew Morton Cc: "Liam R. Howlett" , Matthew Wilcox , linux-mm@kvack.org, linux-kernel@vger.kernel.org, patches@lists.linux.dev, maple-tree@lists.infradead.org, Vlastimil Babka Subject: [PATCH 06/10] mm/mmap/vma_merge: set mid to NULL if not applicable Date: Thu, 9 Mar 2023 12:12:54 +0100 Message-Id: <20230309111258.24079-7-vbabka@suse.cz> X-Mailer: git-send-email 2.39.2 In-Reply-To: <20230309111258.24079-1-vbabka@suse.cz> References: <20230309111258.24079-1-vbabka@suse.cz> Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit There are several places where we test if 'mid' is really the area NNNN in the diagram and the tests have two variants and are non-obvious to follow. Instead, set 'mid' to NULL up-front if it's not the NNNN area, and simplify the tests. Also update the description in comment accordingly. Signed-off-by: Vlastimil Babka --- mm/mmap.c | 21 +++++++++++++-------- 1 file changed, 13 insertions(+), 8 deletions(-) diff --git a/mm/mmap.c b/mm/mmap.c index be60b344e4b1..3396c9b13f1c 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -848,10 +848,11 @@ can_vma_merge_after(struct vm_area_struct *vma, unsigned long vm_flags, * * The following mprotect cases have to be considered, where AAAA is * the area passed down from mprotect_fixup, never extending beyond one - * vma, PPPPPP is the prev vma specified, and NNNNNN the next vma after: + * vma, PPPPPP is the prev vma specified, NNNN is a vma that overlaps + * the area AAAA and XXXXXX the next vma after AAAA: * * AAAA AAAA AAAA - * PPPPPPNNNNNN PPPPPPXXXXXX PPPPPPNNNNNN + * PPPPPPXXXXXX PPPPPPXXXXXX PPPPPPNNNNNN * cannot merge might become might become * PPXXXXXXXXXX PPPPPPPPPPNN * mmap, brk or case 4 below case 5 below @@ -879,9 +880,10 @@ can_vma_merge_after(struct vm_area_struct *vma, unsigned long vm_flags, * * In the code below: * PPPP is represented by *prev - * NNNN is represented by *mid (and possibly equal to *next) - * XXXX is represented by *next or not represented at all. - * AAAA is not represented - it will be merged or the function will return NULL + * NNNN is represented by *mid or not represented at all (NULL) + * XXXX is represented by *next or not represented at all (NULL) + * AAAA is not represented - it will be merged and the vma containing the + * area is returned, or the function will return NULL */ struct vm_area_struct *vma_merge(struct vma_iterator *vmi, struct mm_struct *mm, struct vm_area_struct *prev, unsigned long addr, @@ -918,6 +920,9 @@ struct vm_area_struct *vma_merge(struct vma_iterator *vmi, struct mm_struct *mm, else next = mid; + if (mid && end <= mid->vm_start) + mid = NULL; + /* verify some invariant that must be enforced by the caller */ VM_WARN_ON(prev && addr <= prev->vm_start); VM_WARN_ON(mid && end > mid->vm_end); @@ -952,7 +957,7 @@ struct vm_area_struct *vma_merge(struct vma_iterator *vmi, struct mm_struct *mm, remove = next; /* case 1 */ vma_end = next->vm_end; err = dup_anon_vma(prev, next); - if (mid != next) { /* case 6 */ + if (mid) { /* case 6 */ remove = mid; remove2 = next; if (!next->anon_vma) @@ -960,7 +965,7 @@ struct vm_area_struct *vma_merge(struct vma_iterator *vmi, struct mm_struct *mm, } } else if (merge_prev) { err = 0; /* case 2 */ - if (mid && end > mid->vm_start) { + if (mid) { err = dup_anon_vma(prev, mid); if (end == mid->vm_end) { /* case 7 */ remove = mid; @@ -982,7 +987,7 @@ struct vm_area_struct *vma_merge(struct vma_iterator *vmi, struct mm_struct *mm, vma_end = next->vm_end; vma_pgoff = next->vm_pgoff; err = 0; - if (mid != next) { /* case 8 */ + if (mid) { /* case 8 */ vma_pgoff = mid->vm_pgoff; remove = mid; err = dup_anon_vma(next, mid); -- 2.39.2