From: Anna Schumaker <Anna.Schumaker@xxxxxxxxxx>
I found that the read code might send multiple requests using the same
nfs_pgio_header, but nfs4_proc_read_setup() is only called once. This is
how we ended up occasionally double-freeing the scratch buffer, but also
means we set a NULL pointer but non-zero length to the xdr scratch
buffer. This results in an oops the first time decoding needs to copy
something to scratch, which frequently happens when decoding READ_PLUS
hole segments.
I fix this by moving scratch handling into the pageio read code. I
provide a function to allocate scratch space for decoding read replies,
and free the scratch buffer when the nfs_pgio_header is freed.
Krzysztof Kozlowski hit a bug a while ago with similar symptoms,
and I'm hopeful that this patch fixes his issue.
Reported-by: Krzysztof Kozlowski <krzysztof.kozlowski@xxxxxxxxxx>
Fixes: fbd2a05f29a9 (NFSv4.2: Rework scratch handling for READ_PLUS)
Signed-off-by: Anna Schumaker <Anna.Schumaker@xxxxxxxxxx>
---
v3: Remove accidentally copy-and-pasted line from the commit message
---
fs/nfs/internal.h | 1 +
fs/nfs/nfs42.h | 1 +
fs/nfs/nfs42xdr.c | 2 +-
fs/nfs/nfs4proc.c | 13 +------------
fs/nfs/read.c | 10 ++++++++++
5 files changed, 14 insertions(+), 13 deletions(-)
diff --git a/fs/nfs/internal.h b/fs/nfs/internal.h
index 3cc027d3bd58..1607c23f68d4 100644
--- a/fs/nfs/internal.h
+++ b/fs/nfs/internal.h
@@ -489,6 +489,7 @@ extern const struct nfs_pgio_completion_ops nfs_async_read_completion_ops;
extern void nfs_pageio_init_read(struct nfs_pageio_descriptor *pgio,
struct inode *inode, bool force_mds,
const struct nfs_pgio_completion_ops *compl_ops);
+extern bool nfs_read_alloc_scratch(struct nfs_pgio_header *hdr, size_t size);
extern int nfs_read_add_folio(struct nfs_pageio_descriptor *pgio,
struct nfs_open_context *ctx,
struct folio *folio);
diff --git a/fs/nfs/nfs42.h b/fs/nfs/nfs42.h
index 0fe5aacbcfdf..b59876b01a1e 100644
--- a/fs/nfs/nfs42.h
+++ b/fs/nfs/nfs42.h
@@ -13,6 +13,7 @@
* more? Need to consider not to pre-alloc too much for a compound.
*/
#define PNFS_LAYOUTSTATS_MAXDEV (4)
+#define READ_PLUS_SCRATCH_SIZE (16)
/* nfs4.2proc.c */
#ifdef CONFIG_NFS_V4_2
diff --git a/fs/nfs/nfs42xdr.c b/fs/nfs/nfs42xdr.c
index 75765382cc0e..20aa5e746497 100644
--- a/fs/nfs/nfs42xdr.c
+++ b/fs/nfs/nfs42xdr.c
@@ -1351,7 +1351,7 @@ static int nfs4_xdr_dec_read_plus(struct rpc_rqst *rqstp,
struct compound_hdr hdr;
int status;
- xdr_set_scratch_buffer(xdr, res->scratch, sizeof(res->scratch));
+ xdr_set_scratch_buffer(xdr, res->scratch, READ_PLUS_SCRATCH_SIZE);
status = decode_compound_hdr(xdr, &hdr);
if (status)
diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index d3665390c4cb..73dc8a793ae9 100644
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -5437,18 +5437,8 @@ static bool nfs4_read_plus_not_supported(struct rpc_task *task,
return false;
}
-static inline void nfs4_read_plus_scratch_free(struct nfs_pgio_header *hdr)
-{
- if (hdr->res.scratch) {
- kfree(hdr->res.scratch);
- hdr->res.scratch = NULL;
- }
-}
-
static int nfs4_read_done(struct rpc_task *task, struct nfs_pgio_header *hdr)
{
- nfs4_read_plus_scratch_free(hdr);
-
if (!nfs4_sequence_done(task, &hdr->res.seq_res))
return -EAGAIN;
if (nfs4_read_stateid_changed(task, &hdr->args))
@@ -5468,8 +5458,7 @@ static bool nfs42_read_plus_support(struct nfs_pgio_header *hdr,
/* Note: We don't use READ_PLUS with pNFS yet */
if (nfs_server_capable(hdr->inode, NFS_CAP_READ_PLUS) && !hdr->ds_clp) {
msg->rpc_proc = &nfs4_procedures[NFSPROC4_CLNT_READ_PLUS];
- hdr->res.scratch = kmalloc(32, GFP_KERNEL);
- return hdr->res.scratch != NULL;
+ return nfs_read_alloc_scratch(hdr, READ_PLUS_SCRATCH_SIZE);
}
return false;
}
diff --git a/fs/nfs/read.c b/fs/nfs/read.c
index f71eeee67e20..7dc21a48e3e7 100644
--- a/fs/nfs/read.c
+++ b/fs/nfs/read.c
@@ -47,6 +47,8 @@ static struct nfs_pgio_header *nfs_readhdr_alloc(void)
static void nfs_readhdr_free(struct nfs_pgio_header *rhdr)
{
+ if (rhdr->res.scratch != NULL)
+ kfree(rhdr->res.scratch);
kmem_cache_free(nfs_rdata_cachep, rhdr);
}
@@ -108,6 +110,14 @@ void nfs_pageio_reset_read_mds(struct nfs_pageio_descriptor *pgio)
}
EXPORT_SYMBOL_GPL(nfs_pageio_reset_read_mds);
+bool nfs_read_alloc_scratch(struct nfs_pgio_header *hdr, size_t size)
+{
+ WARN_ON(hdr->res.scratch != NULL);
+ hdr->res.scratch = kmalloc(size, GFP_KERNEL);
+ return hdr->res.scratch != NULL;
+}
+EXPORT_SYMBOL_GPL(nfs_read_alloc_scratch);
+
static void nfs_readpage_release(struct nfs_page *req, int error)
{
struct folio *folio = nfs_page_to_folio(req);
--
2.41.0
