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Subject[PATCH 4.19 65/81] NFS: Fix O_DIRECT accounting of number of bytes read/written
Date
From: Trond Myklebust <trondmy@gmail.com>

commit 031d73ed768a40684f3ca21992265ffdb6a270bf upstream.

When a series of O_DIRECT reads or writes are truncated, either due to
eof or due to an error, then we should return the number of contiguous
bytes that were received/sent starting at the offset specified by the
application.

Currently, we are failing to correctly check contiguity, and so we're
failing the generic/465 in xfstests when the race between the read
and write RPCs causes the file to get extended while the 2 reads are
outstanding. If the first read RPC call wins the race and returns with
eof set, we should treat the second read RPC as being truncated.

Reported-by: Su Yanjun <suyj.fnst@cn.fujitsu.com>
Fixes: 1ccbad9f9f9bd ("nfs: fix DIO good bytes calculation")
Cc: stable@vger.kernel.org # 4.1+
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
fs/nfs/direct.c | 78 ++++++++++++++++++++++++++++++--------------------------
1 file changed, 43 insertions(+), 35 deletions(-)

--- a/fs/nfs/direct.c
+++ b/fs/nfs/direct.c
@@ -122,32 +122,49 @@ static inline int put_dreq(struct nfs_di
}

static void
-nfs_direct_good_bytes(struct nfs_direct_req *dreq, struct nfs_pgio_header *hdr)
+nfs_direct_handle_truncated(struct nfs_direct_req *dreq,
+ const struct nfs_pgio_header *hdr,
+ ssize_t dreq_len)
+{
+ struct nfs_direct_mirror *mirror = &dreq->mirrors[hdr->pgio_mirror_idx];
+
+ if (!(test_bit(NFS_IOHDR_ERROR, &hdr->flags) ||
+ test_bit(NFS_IOHDR_EOF, &hdr->flags)))
+ return;
+ if (dreq->max_count >= dreq_len) {
+ dreq->max_count = dreq_len;
+ if (dreq->count > dreq_len)
+ dreq->count = dreq_len;
+
+ if (test_bit(NFS_IOHDR_ERROR, &hdr->flags))
+ dreq->error = hdr->error;
+ else /* Clear outstanding error if this is EOF */
+ dreq->error = 0;
+ }
+ if (mirror->count > dreq_len)
+ mirror->count = dreq_len;
+}
+
+static void
+nfs_direct_count_bytes(struct nfs_direct_req *dreq,
+ const struct nfs_pgio_header *hdr)
{
- int i;
- ssize_t count;
+ struct nfs_direct_mirror *mirror = &dreq->mirrors[hdr->pgio_mirror_idx];
+ loff_t hdr_end = hdr->io_start + hdr->good_bytes;
+ ssize_t dreq_len = 0;

- WARN_ON_ONCE(dreq->count >= dreq->max_count);
+ if (hdr_end > dreq->io_start)
+ dreq_len = hdr_end - dreq->io_start;

- if (dreq->mirror_count == 1) {
- dreq->mirrors[hdr->pgio_mirror_idx].count += hdr->good_bytes;
- dreq->count += hdr->good_bytes;
- } else {
- /* mirrored writes */
- 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 */
- count = dreq->mirrors[0].count;
+ nfs_direct_handle_truncated(dreq, hdr, dreq_len);

- for (i = 1; i < dreq->mirror_count; i++)
- count = min(count, dreq->mirrors[i].count);
+ if (dreq_len > dreq->max_count)
+ dreq_len = dreq->max_count;

- dreq->count = count;
- }
+ if (mirror->count < dreq_len)
+ mirror->count = dreq_len;
+ if (dreq->count < dreq_len)
+ dreq->count = dreq_len;
}

/*
@@ -401,20 +418,12 @@ static void nfs_direct_read_completion(s
struct nfs_direct_req *dreq = hdr->dreq;

spin_lock(&dreq->lock);
- if (test_bit(NFS_IOHDR_ERROR, &hdr->flags))
- dreq->error = hdr->error;
-
if (test_bit(NFS_IOHDR_REDO, &hdr->flags)) {
spin_unlock(&dreq->lock);
goto out_put;
}

- if (hdr->good_bytes != 0)
- nfs_direct_good_bytes(dreq, hdr);
-
- if (test_bit(NFS_IOHDR_EOF, &hdr->flags))
- dreq->error = 0;
-
+ nfs_direct_count_bytes(dreq, hdr);
spin_unlock(&dreq->lock);

while (!list_empty(&hdr->pages)) {
@@ -651,6 +660,9 @@ static void nfs_direct_write_reschedule(
nfs_direct_write_scan_commit_list(dreq->inode, &reqs, &cinfo);

dreq->count = 0;
+ dreq->max_count = 0;
+ list_for_each_entry(req, &reqs, wb_list)
+ dreq->max_count += req->wb_bytes;
dreq->verf.committed = NFS_INVALID_STABLE_HOW;
nfs_clear_pnfs_ds_commit_verifiers(&dreq->ds_cinfo);
for (i = 0; i < dreq->mirror_count; i++)
@@ -783,17 +795,13 @@ static void nfs_direct_write_completion(
nfs_init_cinfo_from_dreq(&cinfo, dreq);

spin_lock(&dreq->lock);
-
- if (test_bit(NFS_IOHDR_ERROR, &hdr->flags))
- dreq->error = hdr->error;
-
if (test_bit(NFS_IOHDR_REDO, &hdr->flags)) {
spin_unlock(&dreq->lock);
goto out_put;
}

+ nfs_direct_count_bytes(dreq, hdr);
if (hdr->good_bytes != 0) {
- nfs_direct_good_bytes(dreq, hdr);
if (nfs_write_need_commit(hdr)) {
if (dreq->flags == NFS_ODIRECT_RESCHED_WRITES)
request_commit = true;

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