2012-05-29 04:31:50

by Peng Tao

Subject: [PATCH-v2] pnfsblock: bail out partial page IO

Current block layout driver read/write code assumes page
aligned IO in many places. Add a checker to validate the assumption.

Cc: [email protected]
Signed-off-by: Peng Tao <[email protected]>
---
fs/nfs/blocklayout/blocklayout.c | 39 +++++++++++++++++++++++++++++++++++--
1 files changed, 36 insertions(+), 3 deletions(-)

diff --git a/fs/nfs/blocklayout/blocklayout.c b/fs/nfs/blocklayout/blocklayout.c
index 7ae8a60..dd392ed 100644
--- a/fs/nfs/blocklayout/blocklayout.c
+++ b/fs/nfs/blocklayout/blocklayout.c
@@ -228,6 +228,14 @@ bl_end_par_io_read(void *data, int unused)
schedule_work(&rdata->task.u.tk_work);
}

+static bool
+bl_check_alignment(u64 offset, u32 len, unsigned long blkmask)
+{
+ if ((offset & blkmask) || (len & blkmask))
+ return false;
+ return true;
+}
+
static enum pnfs_try_status
bl_read_pagelist(struct nfs_read_data *rdata)
{
@@ -244,6 +252,9 @@ bl_read_pagelist(struct nfs_read_data *rdata)
dprintk("%s enter nr_pages %u offset %lld count %u\n", __func__,
rdata->pages.npages, f_offset, (unsigned int)rdata->args.count);

+ if (!bl_check_alignment(f_offset, rdata->args.count, PAGE_CACHE_MASK))
+ goto use_mds;
+
par = alloc_parallel(rdata);
if (!par)
goto use_mds;
@@ -552,7 +563,7 @@ bl_write_pagelist(struct nfs_write_data *wdata, int sync)
struct bio *bio = NULL;
struct pnfs_block_extent *be = NULL, *cow_read = NULL;
sector_t isect, last_isect = 0, extent_length = 0;
- struct parallel_io *par;
+ struct parallel_io *par = NULL;
loff_t offset = wdata->args.offset;
size_t count = wdata->args.count;
struct page **pages = wdata->args.pages;
@@ -563,6 +574,10 @@ bl_write_pagelist(struct nfs_write_data *wdata, int sync)
NFS_SERVER(header->inode)->pnfs_blksize >> PAGE_CACHE_SHIFT;

dprintk("%s enter, %Zu@%lld\n", __func__, count, offset);
+ /* Check for alignment first */
+ if (!bl_check_alignment(offset, count, PAGE_CACHE_MASK))
+ goto out_mds;
+
/* At this point, wdata->pages is a (sequential) list of nfs_pages.
* We want to write each, and if there is an error set pnfs_error
* to have it redone using nfs.
@@ -996,14 +1011,32 @@ bl_clear_layoutdriver(struct nfs_server *server)
return 0;
}

+static void
+bl_pg_init_read(struct nfs_pageio_descriptor *pgio, struct nfs_page *req)
+{
+ if (!bl_check_alignment(req->wb_offset, req->wb_bytes, PAGE_CACHE_MASK))
+ nfs_pageio_reset_read_mds(pgio);
+ else
+ pnfs_generic_pg_init_read(pgio, req);
+}
+
+static void
+bl_pg_init_write(struct nfs_pageio_descriptor *pgio, struct nfs_page *req)
+{
+ if (!bl_check_alignment(req->wb_offset, req->wb_bytes, PAGE_CACHE_MASK))
+ nfs_pageio_reset_write_mds(pgio);
+ else
+ pnfs_generic_pg_init_write(pgio, req);
+}
+
static const struct nfs_pageio_ops bl_pg_read_ops = {
- .pg_init = pnfs_generic_pg_init_read,
+ .pg_init = bl_pg_init_read,
.pg_test = pnfs_generic_pg_test,
.pg_doio = pnfs_generic_pg_readpages,
};

static const struct nfs_pageio_ops bl_pg_write_ops = {
- .pg_init = pnfs_generic_pg_init_write,
+ .pg_init = bl_pg_init_write,
.pg_test = pnfs_generic_pg_test,
.pg_doio = pnfs_generic_pg_writepages,
};
--
1.7.1.262.g5ef3d

2012-05-29 05:09:38

by Jonathan Nieder

Subject: Re: [PATCH-v2] pnfsblock: bail out partial page IO

Hi,

Peng Tao wrote:

> Current block layout driver read/write code assumes page
> aligned IO in many places. Add a checker to validate the assumption.
>
> Cc: [email protected]
> Signed-off-by: Peng Tao <[email protected]>

Does this fix a build error, oops, hang, data corruption, real
security issue, or other important bug that has been bothering people?

If so, please add a few more words explaining the symptoms in the
commit log. If not, it sounds like a good change but it wouldn't be
suitable for stable.

Hope that helps,
Jonathan