RE: [PATCH 041/270] pnfsblock: fix partial page buffer wirte

From: Peng, Tao
Date: Mon Dec 03 2012 - 21:56:06 EST

> -----Original Message-----
> From: Peng, Tao
> Sent: Saturday, December 01, 2012 11:47 PM
> To: Myklebust, Trond; Greg Kroah-Hartman; Ben Hutchings
> Cc: linux-kernel@xxxxxxxxxxxxxxx; stable@xxxxxxxxxxxxxxx; kernel-team@xxxxxxxxxxxxxxxx; Herton Ronaldo
> Krzesinski
> Subject: RE: [PATCH 041/270] pnfsblock: fix partial page buffer wirte
>
> Hi Greg and Ben,
>
> Attached is the patch of upstream commit fe6e1e8d9fad86873eb74a26e80a8f91f9e870b5 backported to 3.4.20
> stable branch (head 0f4475cfaaf80e34ea5496a93ce579fe8c6950d5).
>
Hi Greg,

Somehow the patch got dropped? I just scanned through the newly released 3.4.21 and it doesn't have the patch.

Is it because the patch was sent as attachment? My apology for that... I'm resending it bellow. It applies cleanly on top of 3.4.21 (commit 3d514b82). Please queue it for the next 3.4 stable release. Thanks!

Best,
Tao

From bb51f7df0688f137998c3746705a346c7d8323c2 Mon Sep 17 00:00:00 2001
From: Peng Tao <bergwolf@xxxxxxxxx>
Date: Fri, 24 Aug 2012 00:27:51 +0800
Subject: [PATCH] pnfsblock: fix partial page buffer wirte

commit fe6e1e8d9fad86873eb74a26e80a8f91f9e870b5 upstream.

If applications use flock to protect its write range, generic NFS
will not do read-modify-write cycle at page cache level. Therefore
LD should know how to handle non-sector aligned writes. Otherwise
there will be data corruption.

Signed-off-by: Peng Tao <tao.peng@xxxxxxx>
Signed-off-by: Trond Myklebust <Trond.Myklebust@xxxxxxxxxx>
---
fs/nfs/blocklayout/blocklayout.c | 176 +++++++++++++++++++++++++++++++++++---
fs/nfs/blocklayout/blocklayout.h | 1 +
2 files changed, 165 insertions(+), 12 deletions(-)

diff --git a/fs/nfs/blocklayout/blocklayout.c b/fs/nfs/blocklayout/blocklayout.c
index 7f6a23f..d16dae2 100644
--- a/fs/nfs/blocklayout/blocklayout.c
+++ b/fs/nfs/blocklayout/blocklayout.c
@@ -162,25 +162,39 @@ static struct bio *bl_alloc_init_bio(int npg, sector_t isect,
return bio;
}

-static struct bio *bl_add_page_to_bio(struct bio *bio, int npg, int rw,
+static struct bio *do_add_page_to_bio(struct bio *bio, int npg, int rw,
sector_t isect, struct page *page,
struct pnfs_block_extent *be,
void (*end_io)(struct bio *, int err),
- struct parallel_io *par)
+ struct parallel_io *par,
+ unsigned int offset, int len)
{
+ isect = isect + (offset >> SECTOR_SHIFT);
+ dprintk("%s: npg %d rw %d isect %llu offset %u len %d\n", __func__,
+ npg, rw, (unsigned long long)isect, offset, len);
retry:
if (!bio) {
bio = bl_alloc_init_bio(npg, isect, be, end_io, par);
if (!bio)
return ERR_PTR(-ENOMEM);
}
- if (bio_add_page(bio, page, PAGE_CACHE_SIZE, 0) < PAGE_CACHE_SIZE) {
+ if (bio_add_page(bio, page, len, offset) < len) {
bio = bl_submit_bio(rw, bio);
goto retry;
}
return bio;
}

+static struct bio *bl_add_page_to_bio(struct bio *bio, int npg, int rw,
+ sector_t isect, struct page *page,
+ struct pnfs_block_extent *be,
+ void (*end_io)(struct bio *, int err),
+ struct parallel_io *par)
+{
+ return do_add_page_to_bio(bio, npg, rw, isect, page, be,
+ end_io, par, 0, PAGE_CACHE_SIZE);
+}
+
/* This is basically copied from mpage_end_io_read */
static void bl_end_io_read(struct bio *bio, int err)
{
@@ -443,6 +457,107 @@ map_block(struct buffer_head *bh, sector_t isect, struct pnfs_block_extent *be)
return;
}

+static void
+bl_read_single_end_io(struct bio *bio, int error)
+{
+ struct bio_vec *bvec = bio->bi_io_vec + bio->bi_vcnt - 1;
+ struct page *page = bvec->bv_page;
+
+ /* Only one page in bvec */
+ unlock_page(page);
+}
+
+static int
+bl_do_readpage_sync(struct page *page, struct pnfs_block_extent *be,
+ unsigned int offset, unsigned int len)
+{
+ struct bio *bio;
+ struct page *shadow_page;
+ sector_t isect;
+ char *kaddr, *kshadow_addr;
+ int ret = 0;
+
+ dprintk("%s: offset %u len %u\n", __func__, offset, len);
+
+ shadow_page = alloc_page(GFP_NOFS | __GFP_HIGHMEM);
+ if (shadow_page == NULL)
+ return -ENOMEM;
+
+ bio = bio_alloc(GFP_NOIO, 1);
+ if (bio == NULL)
+ return -ENOMEM;
+
+ isect = (page->index << PAGE_CACHE_SECTOR_SHIFT) +
+ (offset / SECTOR_SIZE);
+
+ bio->bi_sector = isect - be->be_f_offset + be->be_v_offset;
+ bio->bi_bdev = be->be_mdev;
+ bio->bi_end_io = bl_read_single_end_io;
+
+ lock_page(shadow_page);
+ if (bio_add_page(bio, shadow_page,
+ SECTOR_SIZE, round_down(offset, SECTOR_SIZE)) == 0) {
+ unlock_page(shadow_page);
+ bio_put(bio);
+ return -EIO;
+ }
+
+ submit_bio(READ, bio);
+ wait_on_page_locked(shadow_page);
+ if (unlikely(!test_bit(BIO_UPTODATE, &bio->bi_flags))) {
+ ret = -EIO;
+ } else {
+ kaddr = kmap_atomic(page);
+ kshadow_addr = kmap_atomic(shadow_page);
+ memcpy(kaddr + offset, kshadow_addr + offset, len);
+ kunmap_atomic(kshadow_addr);
+ kunmap_atomic(kaddr);
+ }
+ __free_page(shadow_page);
+ bio_put(bio);
+
+ return ret;
+}
+
+static int
+bl_read_partial_page_sync(struct page *page, struct pnfs_block_extent *be,
+ unsigned int dirty_offset, unsigned int dirty_len,
+ bool full_page)
+{
+ int ret = 0;
+ unsigned int start, end;
+
+ if (full_page) {
+ start = 0;
+ end = PAGE_CACHE_SIZE;
+ } else {
+ start = round_down(dirty_offset, SECTOR_SIZE);
+ end = round_up(dirty_offset + dirty_len, SECTOR_SIZE);
+ }
+
+ dprintk("%s: offset %u len %d\n", __func__, dirty_offset, dirty_len);
+ if (!be) {
+ zero_user_segments(page, start, dirty_offset,
+ dirty_offset + dirty_len, end);
+ if (start == 0 && end == PAGE_CACHE_SIZE &&
+ trylock_page(page)) {
+ SetPageUptodate(page);
+ unlock_page(page);
+ }
+ return ret;
+ }
+
+ if (start != dirty_offset)
+ ret = bl_do_readpage_sync(page, be, start,
+ dirty_offset - start);
+
+ if (!ret && (dirty_offset + dirty_len < end))
+ ret = bl_do_readpage_sync(page, be, dirty_offset + dirty_len,
+ end - dirty_offset - dirty_len);
+
+ return ret;
+}
+
/* Given an unmapped page, zero it or read in page for COW, page is locked
* by caller.
*/
@@ -476,7 +591,6 @@ init_page_for_write(struct page *page, struct pnfs_block_extent *cow_read)
SetPageUptodate(page);

cleanup:
- bl_put_extent(cow_read);
if (bh)
free_buffer_head(bh);
if (ret) {
@@ -547,6 +661,7 @@ bl_write_pagelist(struct nfs_write_data *wdata, int sync)
struct parallel_io *par;
loff_t offset = wdata->args.offset;
size_t count = wdata->args.count;
+ unsigned int pg_offset, pg_len, saved_len;
struct page **pages = wdata->args.pages;
struct page *page;
pgoff_t index;
@@ -651,10 +766,11 @@ next_page:
if (!extent_length) {
/* We've used up the previous extent */
bl_put_extent(be);
+ bl_put_extent(cow_read);
bio = bl_submit_bio(WRITE, bio);
/* Get the next one */
be = bl_find_get_extent(BLK_LSEG2EXT(wdata->lseg),
- isect, NULL);
+ isect, &cow_read);
if (!be || !is_writable(be, isect)) {
wdata->pnfs_error = -EINVAL;
goto out;
@@ -671,7 +787,26 @@ next_page:
extent_length = be->be_length -
(isect - be->be_f_offset);
}
- if (be->be_state == PNFS_BLOCK_INVALID_DATA) {
+
+ dprintk("%s offset %lld count %Zu\n", __func__, offset, count);
+ pg_offset = offset & ~PAGE_CACHE_MASK;
+ if (pg_offset + count > PAGE_CACHE_SIZE)
+ pg_len = PAGE_CACHE_SIZE - pg_offset;
+ else
+ pg_len = count;
+
+ saved_len = pg_len;
+ if (be->be_state == PNFS_BLOCK_INVALID_DATA &&
+ !bl_is_sector_init(be->be_inval, isect)) {
+ ret = bl_read_partial_page_sync(pages[i], cow_read,
+ pg_offset, pg_len, true);
+ if (ret) {
+ dprintk("%s bl_read_partial_page_sync fail %d\n",
+ __func__, ret);
+ wdata->pnfs_error = ret;
+ goto out;
+ }
+
ret = bl_mark_sectors_init(be->be_inval, isect,
PAGE_CACHE_SECTORS);
if (unlikely(ret)) {
@@ -680,15 +815,33 @@ next_page:
wdata->pnfs_error = ret;
goto out;
}
+
+ /* Expand to full page write */
+ pg_offset = 0;
+ pg_len = PAGE_CACHE_SIZE;
+ } else if ((pg_offset & (SECTOR_SIZE - 1)) ||
+ (pg_len & (SECTOR_SIZE - 1))) {
+ /* ahh, nasty case. We have to do sync full sector
+ * read-modify-write cycles.
+ */
+ unsigned int saved_offset = pg_offset;
+ ret = bl_read_partial_page_sync(pages[i], be, pg_offset,
+ pg_len, false);
+ pg_offset = round_down(pg_offset, SECTOR_SIZE);
+ pg_len = round_up(saved_offset + pg_len, SECTOR_SIZE)
+ - pg_offset;
}
- bio = bl_add_page_to_bio(bio, wdata->npages - i, WRITE,
+ bio = do_add_page_to_bio(bio, wdata->npages - i, WRITE,
isect, pages[i], be,
- bl_end_io_write, par);
+ bl_end_io_write, par,
+ pg_offset, pg_len);
if (IS_ERR(bio)) {
wdata->pnfs_error = PTR_ERR(bio);
bio = NULL;
goto out;
}
+ offset += saved_len;
+ count -= saved_len;
isect += PAGE_CACHE_SECTORS;
last_isect = isect;
extent_length -= PAGE_CACHE_SECTORS;
@@ -706,17 +859,16 @@ next_page:
}

write_done:
- wdata->res.count = (last_isect << SECTOR_SHIFT) - (offset);
- if (count < wdata->res.count) {
- wdata->res.count = count;
- }
+ wdata->res.count = wdata->args.count;
out:
bl_put_extent(be);
+ bl_put_extent(cow_read);
bl_submit_bio(WRITE, bio);
put_parallel(par);
return PNFS_ATTEMPTED;
out_mds:
bl_put_extent(be);
+ bl_put_extent(cow_read);
kfree(par);
return PNFS_NOT_ATTEMPTED;
}
diff --git a/fs/nfs/blocklayout/blocklayout.h b/fs/nfs/blocklayout/blocklayout.h
index 0335069..39bb51a 100644
--- a/fs/nfs/blocklayout/blocklayout.h
+++ b/fs/nfs/blocklayout/blocklayout.h
@@ -41,6 +41,7 @@

#define PAGE_CACHE_SECTORS (PAGE_CACHE_SIZE >> SECTOR_SHIFT)
#define PAGE_CACHE_SECTOR_SHIFT (PAGE_CACHE_SHIFT - SECTOR_SHIFT)
+#define SECTOR_SIZE (1 << SECTOR_SHIFT)

struct block_mount_id {
spinlock_t bm_lock; /* protects list */
--
1.7.9.5

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