[ 088/147] pnfsblock: fix partial page buffer wirte

Ben Hutchings
2012-10-14T14:43:21Z

From: Peng Tao <bergwolf@gmail.com>

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@emc.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
[bwh: Backported to Linux 3.2:
- Adjust context
- s/wdata->pages\.npages/wdata->npages/
- s/header->pnfs_error/wdata->pnfs_error/
- Drop change in missing out_mds exit path]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
fs/nfs/blocklayout/blocklayout.c | 177 +++++++++++++++++++++++++++++++++++---
fs/nfs/blocklayout/blocklayout.h | 1 +
2 files changed, 166 insertions(+), 12 deletions(-)

--- a/fs/nfs/blocklayout/blocklayout.c
+++ b/fs/nfs/blocklayout/blocklayout.c
@@ -164,25 +164,39 @@ static struct bio *bl_alloc_init_bio(int
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)
{
@@ -446,6 +460,106 @@ map_block(struct buffer_head *bh, sector
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.
*/
@@ -479,7 +593,6 @@ init_page_for_write(struct page *page, s
SetPageUptodate(page);

cleanup:
- bl_put_extent(cow_read);
if (bh)
free_buffer_head(bh);
if (ret) {
@@ -501,6 +614,7 @@ bl_write_pagelist(struct nfs_write_data
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;
@@ -615,10 +729,11 @@ 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;
@@ -626,7 +741,26 @@ 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,
NULL);
@@ -636,15 +770,35 @@ 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;
@@ -662,12 +816,10 @@ 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;
--- a/fs/nfs/blocklayout/blocklayout.h
+++ b/fs/nfs/blocklayout/blocklayout.h
@@ -40,6 +40,7 @@

#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 */