nfs: count DIO good bytes correctly with mirroring

When resending to MDS, we might resend multiple mirroring
requests to MDS. As a result, nfs_direct_good_bytes() ends
up counting bytes multiple times, causing application to
get wrong return results in read/write syscalls.

Fix it by tracking start of a dreq and checking the range of
pgio header.

Cc: Weston Andros Adamson <dros@primarydata.com>
Signed-off-by: Peng Tao <tao.peng@primarydata.com>

diff --git a/fs/nfs/direct.c b/fs/nfs/direct.c
index 4fad6b727eb441c69ce755bb59146576b180fcc3..3715b4957abc0a369e0ade7e80a587d531028cc7 100644 (file)
--- a/fs/nfs/direct.c
+++ b/fs/nfs/direct.c
@@ -88,6 +88,7 @@ struct nfs_direct_req {
 
        ssize_t                 count,          /* bytes actually processed */
                                bytes_left,     /* bytes left to be sent */
+                               io_start,       /* start of IO */
                                error;          /* any reported error */
        struct completion       completion;     /* wait for i/o completion */
 
@@ -130,10 +131,11 @@ nfs_direct_good_bytes(struct nfs_direct_req *dreq, struct nfs_pgio_header *hdr)
 
        WARN_ON_ONCE(hdr->pgio_mirror_idx >= dreq->mirror_count);
 
-       dreq->mirrors[hdr->pgio_mirror_idx].count += hdr->good_bytes;
-
-       if (hdr->pgio_mirror_idx == 0)
-               dreq->count += hdr->good_bytes;
+       count = dreq->mirrors[hdr->pgio_mirror_idx].count;
+       if (count + dreq->io_start < hdr->io_start + hdr->good_bytes) {
+               count = hdr->io_start + hdr->good_bytes - dreq->io_start;
+               dreq->mirrors[hdr->pgio_mirror_idx].count = count;
+       }
 
        /* update the dreq->count by finding the minimum agreed count from all
         * mirrors */
@@ -594,6 +596,7 @@ ssize_t nfs_file_direct_read(struct kiocb *iocb, struct iov_iter *iter,
 
        dreq->inode = inode;
        dreq->bytes_left = count;
+       dreq->io_start = pos;
        dreq->ctx = get_nfs_open_context(nfs_file_open_context(iocb->ki_filp));
        l_ctx = nfs_get_lock_context(dreq->ctx);
        if (IS_ERR(l_ctx)) {
@@ -1002,6 +1005,7 @@ ssize_t nfs_file_direct_write(struct kiocb *iocb, struct iov_iter *iter,
 
        dreq->inode = inode;
        dreq->bytes_left = count;
+       dreq->io_start = pos;
        dreq->ctx = get_nfs_open_context(nfs_file_open_context(iocb->ki_filp));
        l_ctx = nfs_get_lock_context(dreq->ctx);
        if (IS_ERR(l_ctx)) {