From 5bb6ce3aeb02497668a4e8971268b041aa61de8d Mon Sep 17 00:00:00 2001 From: "Fabio M. De Francesco" Date: Mon, 1 Aug 2022 14:27:09 +0200 Subject: [PATCH] fs/isofs: replace kmap() with kmap_local_page() MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit The use of kmap() is being deprecated in favor of kmap_local_page(). There are two main problems with kmap(): (1) It comes with an overhead as mapping space is restricted and protected by a global lock for synchronization and (2) it also requires global TLB invalidation when the kmap's pool wraps and it might block when the mapping space is fully utilized until a slot becomes available. With kmap_local_page() the mappings are per thread, CPU local, can take page faults, and can be called from any context (including interrupts). Tasks can be preempted and, when scheduled to run again, the kernel virtual addresses are restored and still valid. It is faster than kmap() in kernels with HIGHMEM enabled. Since kmap_local_page() can be safely used in compress.c, it should be called everywhere instead of kmap(). Therefore, replace kmap() with kmap_local_page() in compress.c. Where it is needed, use memzero_page() instead of open coding kmap_local_page() plus memset() to fill the pages with zeros. Delete the redundant flush_dcache_page() in the two call sites of memzero_page(). Tested with mkisofs on a QEMU/KVM x86_32 VM, 6GB RAM, booting a kernel with HIGHMEM64GB enabled. Link: https://lkml.kernel.org/r/20220801122709.8164-1-fmdefrancesco@gmail.com Signed-off-by: Fabio M. De Francesco Suggested-by: Ira Weiny Reviewed-by: Jan Kara Cc: Matthew Wilcox (Oracle) Cc: Roman Gushchin Cc: Pali Rohár Cc: Muchun Song Cc: Theodore Ts'o Signed-off-by: Andrew Morton --- fs/isofs/compress.c | 20 ++++++++++---------- 1 file changed, 10 insertions(+), 10 deletions(-) diff --git a/fs/isofs/compress.c b/fs/isofs/compress.c index b466172eec25..09285e82eb08 100644 --- a/fs/isofs/compress.c +++ b/fs/isofs/compress.c @@ -67,8 +67,7 @@ static loff_t zisofs_uncompress_block(struct inode *inode, loff_t block_start, for ( i = 0 ; i < pcount ; i++ ) { if (!pages[i]) continue; - memset(page_address(pages[i]), 0, PAGE_SIZE); - flush_dcache_page(pages[i]); + memzero_page(pages[i], 0, PAGE_SIZE); SetPageUptodate(pages[i]); } return ((loff_t)pcount) << PAGE_SHIFT; @@ -120,7 +119,7 @@ static loff_t zisofs_uncompress_block(struct inode *inode, loff_t block_start, zerr != Z_STREAM_END) { if (!stream.avail_out) { if (pages[curpage]) { - stream.next_out = page_address(pages[curpage]) + stream.next_out = kmap_local_page(pages[curpage]) + poffset; stream.avail_out = PAGE_SIZE - poffset; poffset = 0; @@ -176,6 +175,10 @@ static loff_t zisofs_uncompress_block(struct inode *inode, loff_t block_start, flush_dcache_page(pages[curpage]); SetPageUptodate(pages[curpage]); } + if (stream.next_out != (unsigned char *)zisofs_sink_page) { + kunmap_local(stream.next_out); + stream.next_out = NULL; + } curpage++; } if (!stream.avail_in) @@ -183,6 +186,8 @@ static loff_t zisofs_uncompress_block(struct inode *inode, loff_t block_start, } inflate_out: zlib_inflateEnd(&stream); + if (stream.next_out && stream.next_out != (unsigned char *)zisofs_sink_page) + kunmap_local(stream.next_out); z_eio: mutex_unlock(&zisofs_zlib_lock); @@ -283,9 +288,7 @@ static int zisofs_fill_pages(struct inode *inode, int full_page, int pcount, } if (poffset && *pages) { - memset(page_address(*pages) + poffset, 0, - PAGE_SIZE - poffset); - flush_dcache_page(*pages); + memzero_page(*pages, poffset, PAGE_SIZE - poffset); SetPageUptodate(*pages); } return 0; @@ -343,10 +346,8 @@ static int zisofs_read_folio(struct file *file, struct folio *folio) for (i = 0; i < pcount; i++, index++) { if (i != full_page) pages[i] = grab_cache_page_nowait(mapping, index); - if (pages[i]) { + if (pages[i]) ClearPageError(pages[i]); - kmap(pages[i]); - } } err = zisofs_fill_pages(inode, full_page, pcount, pages); @@ -357,7 +358,6 @@ static int zisofs_read_folio(struct file *file, struct folio *folio) flush_dcache_page(pages[i]); if (i == full_page && err) SetPageError(pages[i]); - kunmap(pages[i]); unlock_page(pages[i]); if (i != full_page) put_page(pages[i]);