From: Matthew Wilcox <willy@infradead.org>
To: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: "Theodore Ts'o" <tytso@mit.edu>,
Andreas Dilger <adilger.kernel@dilger.ca>,
Jan Kara <jack@suse.com>,
Andrew Morton <akpm@linux-foundation.org>,
Alexander Viro <viro@zeniv.linux.org.uk>,
Hugh Dickins <hughd@google.com>,
Andrea Arcangeli <aarcange@redhat.com>,
Dave Hansen <dave.hansen@intel.com>,
Vlastimil Babka <vbabka@suse.cz>,
Ross Zwisler <ross.zwisler@linux.intel.com>,
linux-ext4@vger.kernel.org, linux-fsdevel@vger.kernel.org,
linux-kernel@vger.kernel.org, linux-mm@kvack.org,
linux-block@vger.kernel.org
Subject: Re: [PATCHv6 12/37] brd: make it handle huge pages
Date: Fri, 10 Feb 2017 09:24:01 -0800 [thread overview]
Message-ID: <20170210172401.GB2267@bombadil.infradead.org> (raw)
In-Reply-To: <20170126115819.58875-13-kirill.shutemov@linux.intel.com>
On Thu, Jan 26, 2017 at 02:57:54PM +0300, Kirill A. Shutemov wrote:
> Do not assume length of bio segment is never larger than PAGE_SIZE.
> With huge pages it's HPAGE_PMD_SIZE (2M on x86-64).
I don't think we even need hugepages for BRD to be buggy. I think there are
already places which allocate compound pages (not in highmem, obviously ...)
and put them in biovecs. So this is pure and simple a bugfix.
That said, I find the current code in brd a bit inelegant, and I don't
think this patch helps... indeed, I think it's buggy:
> @@ -202,12 +202,15 @@ static int copy_to_brd_setup(struct brd_device *brd, sector_t sector, size_t n)
> size_t copy;
>
> copy = min_t(size_t, n, PAGE_SIZE - offset);
> + n -= copy;
> if (!brd_insert_page(brd, sector))
> return -ENOSPC;
> - if (copy < n) {
> + while (n) {
> sector += copy >> SECTOR_SHIFT;
> if (!brd_insert_page(brd, sector))
> return -ENOSPC;
> + copy = min_t(size_t, n, PAGE_SIZE);
> + n -= copy;
> }
We're decrementing 'n' to 0, then testing it, so we never fill in the
last page ... right?
Anyway, here's my effort. Untested.
diff --git a/drivers/block/brd.c b/drivers/block/brd.c
index 3adc32a3153b..0802a6abcd81 100644
--- a/drivers/block/brd.c
+++ b/drivers/block/brd.c
@@ -202,12 +202,14 @@ static int copy_to_brd_setup(struct brd_device *brd, sector_t sector, size_t n)
size_t copy;
copy = min_t(size_t, n, PAGE_SIZE - offset);
- if (!brd_insert_page(brd, sector))
- return -ENOSPC;
- if (copy < n) {
- sector += copy >> SECTOR_SHIFT;
+ for (;;) {
if (!brd_insert_page(brd, sector))
return -ENOSPC;
+ n -= copy;
+ if (!n)
+ break;
+ sector += copy >> SECTOR_SHIFT;
+ copy = min_t(size_t, n, PAGE_SIZE);
}
return 0;
}
@@ -239,26 +241,23 @@ static void copy_to_brd(struct brd_device *brd, const void *src,
struct page *page;
void *dst;
unsigned int offset = (sector & (PAGE_SECTORS-1)) << SECTOR_SHIFT;
- size_t copy;
+ size_t copy = min_t(size_t, n, PAGE_SIZE - offset);
- copy = min_t(size_t, n, PAGE_SIZE - offset);
- page = brd_lookup_page(brd, sector);
- BUG_ON(!page);
-
- dst = kmap_atomic(page);
- memcpy(dst + offset, src, copy);
- kunmap_atomic(dst);
-
- if (copy < n) {
- src += copy;
- sector += copy >> SECTOR_SHIFT;
- copy = n - copy;
+ for (;;) {
page = brd_lookup_page(brd, sector);
BUG_ON(!page);
dst = kmap_atomic(page);
- memcpy(dst, src, copy);
+ memcpy(dst + offset, src, copy);
kunmap_atomic(dst);
+
+ n -= copy;
+ if (!n)
+ break;
+ src += copy;
+ sector += copy >> SECTOR_SHIFT;
+ offset = 0;
+ copy = min_t(size_t, n, PAGE_SIZE);
}
}
@@ -271,28 +270,24 @@ static void copy_from_brd(void *dst, struct brd_device *brd,
struct page *page;
void *src;
unsigned int offset = (sector & (PAGE_SECTORS-1)) << SECTOR_SHIFT;
- size_t copy;
+ size_t copy = min_t(size_t, n, PAGE_SIZE - offset);
- copy = min_t(size_t, n, PAGE_SIZE - offset);
- page = brd_lookup_page(brd, sector);
- if (page) {
- src = kmap_atomic(page);
- memcpy(dst, src + offset, copy);
- kunmap_atomic(src);
- } else
- memset(dst, 0, copy);
-
- if (copy < n) {
- dst += copy;
- sector += copy >> SECTOR_SHIFT;
- copy = n - copy;
+ for (;;) {
page = brd_lookup_page(brd, sector);
if (page) {
src = kmap_atomic(page);
- memcpy(dst, src, copy);
+ memcpy(dst, src + offset, copy);
kunmap_atomic(src);
} else
memset(dst, 0, copy);
+
+ n -= copy;
+ if (!n)
+ break;
+ dst += copy;
+ sector += copy >> SECTOR_SHIFT;
+ offset = 0;
+ copy = min_t(size_t, n, PAGE_SIZE);
}
}
next prev parent reply other threads:[~2017-02-10 18:08 UTC|newest]
Thread overview: 67+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-01-26 11:57 [PATCHv6 00/37] ext4: support of huge pages Kirill A. Shutemov
2017-01-26 11:57 ` [PATCHv6 01/37] mm, shmem: swich huge tmpfs to multi-order radix-tree entries Kirill A. Shutemov
2017-02-09 3:57 ` Matthew Wilcox
2017-02-09 16:58 ` Kirill A. Shutemov
2017-02-13 13:43 ` Kirill A. Shutemov
2017-01-26 11:57 ` [PATCHv6 02/37] Revert "radix-tree: implement radix_tree_maybe_preload_order()" Kirill A. Shutemov
2017-01-26 15:38 ` Matthew Wilcox
2017-01-26 11:57 ` [PATCHv6 03/37] page-flags: relax page flag policy for few flags Kirill A. Shutemov
2017-02-09 4:01 ` Matthew Wilcox
2017-02-13 13:59 ` Kirill A. Shutemov
2017-01-26 11:57 ` [PATCHv6 04/37] mm, rmap: account file thp pages Kirill A. Shutemov
2017-02-09 20:17 ` Matthew Wilcox
2017-01-26 11:57 ` [PATCHv6 05/37] thp: try to free page's buffers before attempt split Kirill A. Shutemov
2017-02-09 20:14 ` Matthew Wilcox
2017-02-13 14:32 ` Kirill A. Shutemov
2017-01-26 11:57 ` [PATCHv6 06/37] thp: handle write-protection faults for file THP Kirill A. Shutemov
2017-01-26 15:44 ` Matthew Wilcox
2017-01-26 15:57 ` Kirill A. Shutemov
2017-02-09 20:19 ` Matthew Wilcox
2017-01-26 11:57 ` [PATCHv6 07/37] filemap: allocate huge page in page_cache_read(), if allowed Kirill A. Shutemov
2017-02-09 21:18 ` Matthew Wilcox
2017-02-13 15:17 ` Kirill A. Shutemov
2017-01-26 11:57 ` [PATCHv6 08/37] filemap: handle huge pages in do_generic_file_read() Kirill A. Shutemov
2017-02-09 21:55 ` Matthew Wilcox
2017-02-13 15:33 ` Kirill A. Shutemov
2017-02-13 16:01 ` Matthew Wilcox
2017-02-13 16:09 ` Matthew Wilcox
2017-02-13 16:28 ` Matthew Wilcox
2017-01-26 11:57 ` [PATCHv6 09/37] filemap: allocate huge page in pagecache_get_page(), if allowed Kirill A. Shutemov
2017-02-09 21:59 ` Matthew Wilcox
2017-01-26 11:57 ` [PATCHv6 10/37] filemap: handle huge pages in filemap_fdatawait_range() Kirill A. Shutemov
2017-02-09 23:03 ` Matthew Wilcox
2017-01-26 11:57 ` [PATCHv6 11/37] HACK: readahead: alloc huge pages, if allowed Kirill A. Shutemov
2017-02-09 23:34 ` Matthew Wilcox
2017-02-10 0:23 ` Andreas Dilger
2017-02-10 14:51 ` Matthew Wilcox
2017-01-26 11:57 ` [PATCHv6 12/37] brd: make it handle huge pages Kirill A. Shutemov
2017-02-10 17:24 ` Matthew Wilcox [this message]
2017-01-26 11:57 ` [PATCHv6 13/37] mm: make write_cache_pages() work on " Kirill A. Shutemov
2017-02-10 17:46 ` Matthew Wilcox
2017-01-26 11:57 ` [PATCHv6 14/37] thp: introduce hpage_size() and hpage_mask() Kirill A. Shutemov
2017-01-26 11:57 ` [PATCHv6 15/37] thp: do not threat slab pages as huge in hpage_{nr_pages,size,mask} Kirill A. Shutemov
2017-02-10 22:13 ` Matthew Wilcox
2017-01-26 11:57 ` [PATCHv6 16/37] thp: make thp_get_unmapped_area() respect S_HUGE_MODE Kirill A. Shutemov
2017-02-10 17:50 ` Matthew Wilcox
2017-01-26 11:57 ` [PATCHv6 17/37] fs: make block_read_full_page() be able to read huge page Kirill A. Shutemov
2017-02-10 17:58 ` Matthew Wilcox
2017-01-26 11:58 ` [PATCHv6 18/37] fs: make block_write_{begin,end}() be able to handle huge pages Kirill A. Shutemov
2017-01-26 11:58 ` [PATCHv6 19/37] fs: make block_page_mkwrite() aware about " Kirill A. Shutemov
2017-01-26 11:58 ` [PATCHv6 20/37] truncate: make truncate_inode_pages_range() " Kirill A. Shutemov
2017-01-26 11:58 ` [PATCHv6 21/37] truncate: make invalidate_inode_pages2_range() " Kirill A. Shutemov
2017-01-26 11:58 ` [PATCHv6 22/37] mm, hugetlb: switch hugetlbfs to multi-order radix-tree entries Kirill A. Shutemov
2017-01-26 11:58 ` [PATCHv6 23/37] mm: account huge pages to dirty, writaback, reclaimable, etc Kirill A. Shutemov
2017-01-26 11:58 ` [PATCHv6 24/37] ext4: make ext4_mpage_readpages() hugepage-aware Kirill A. Shutemov
2017-01-26 11:58 ` [PATCHv6 25/37] ext4: make ext4_writepage() work on huge pages Kirill A. Shutemov
2017-01-26 11:58 ` [PATCHv6 26/37] ext4: handle huge pages in ext4_page_mkwrite() Kirill A. Shutemov
2017-01-26 11:58 ` [PATCHv6 27/37] ext4: handle huge pages in __ext4_block_zero_page_range() Kirill A. Shutemov
2017-01-26 11:58 ` [PATCHv6 28/37] ext4: make ext4_block_write_begin() aware about huge pages Kirill A. Shutemov
2017-01-26 11:58 ` [PATCHv6 29/37] ext4: handle huge pages in ext4_da_write_end() Kirill A. Shutemov
2017-01-26 11:58 ` [PATCHv6 30/37] ext4: make ext4_da_page_release_reservation() aware about huge pages Kirill A. Shutemov
2017-01-26 11:58 ` [PATCHv6 31/37] ext4: handle writeback with " Kirill A. Shutemov
2017-01-26 11:58 ` [PATCHv6 32/37] ext4: make EXT4_IOC_MOVE_EXT work " Kirill A. Shutemov
2017-01-26 11:58 ` [PATCHv6 33/37] ext4: fix SEEK_DATA/SEEK_HOLE for " Kirill A. Shutemov
2017-01-26 11:58 ` [PATCHv6 34/37] ext4: make fallocate() operations work with " Kirill A. Shutemov
2017-01-26 11:58 ` [PATCHv6 35/37] ext4: reserve larger jounral transaction for " Kirill A. Shutemov
2017-01-26 11:58 ` [PATCHv6 36/37] mm, fs, ext4: expand use of page_mapping() and page_to_pgoff() Kirill A. Shutemov
2017-01-26 11:58 ` [PATCHv6 37/37] ext4, vfs: add huge= mount option Kirill A. Shutemov
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