[PATCH 2/4] NFS: Ensure nfs_readpage returns promptly when internal error occurs

Dave Wysochanski
2021-06-28T17:39:12Z

A previous refactoring of nfs_readpage() might end up calling
wait_on_page_locked_killable() even if readpage_async_filler() failed
with an internal error and pg_error was non-zero (for example, if
nfs_create_request() failed). In the case of an internal error,
skip over wait_on_page_locked_killable() as this is only needed
when the read is sent and an error occurs during completion handling.

Signed-off-by: Dave Wysochanski <dwysocha@redhat.com>
---
fs/nfs/read.c | 21 ++++++++++++---------
1 file changed, 12 insertions(+), 9 deletions(-)

diff --git a/fs/nfs/read.c b/fs/nfs/read.c
index 684a730f6670..b0680351df23 100644
--- a/fs/nfs/read.c
+++ b/fs/nfs/read.c
@@ -74,7 +74,7 @@ void nfs_pageio_init_read(struct nfs_pageio_descriptor *pgio,
}
EXPORT_SYMBOL_GPL(nfs_pageio_init_read);

-static void nfs_pageio_complete_read(struct nfs_pageio_descriptor *pgio)
+static int nfs_pageio_complete_read(struct nfs_pageio_descriptor *pgio)
{
struct nfs_pgio_mirror *pgm;
unsigned long npages;
@@ -88,6 +88,8 @@ static void nfs_pageio_complete_read(struct nfs_pageio_descriptor *pgio)
NFS_I(pgio->pg_inode)->read_io += pgm->pg_bytes_written;
npages = (pgm->pg_bytes_written + PAGE_SIZE - 1) >> PAGE_SHIFT;
nfs_add_stats(pgio->pg_inode, NFSIOS_READPAGES, npages);
+
+ return pgio->pg_error < 0 ? pgio->pg_error : 0;
}

@@ -373,16 +375,17 @@ int nfs_readpage(struct file *file, struct page *page)
&nfs_async_read_completion_ops);

ret = readpage_async_filler(&desc, page);
+ if (ret)
+ goto out;

- if (!ret)
- nfs_pageio_complete_read(&desc.pgio);
+ ret = nfs_pageio_complete_read(&desc.pgio);
+ if (ret)
+ goto out;
+
+ ret = wait_on_page_locked_killable(page);
+ if (!PageUptodate(page) && !ret)
+ ret = xchg(&desc.ctx->error, 0);

- ret = desc.pgio.pg_error < 0 ? desc.pgio.pg_error : 0;
- if (!ret) {
- ret = wait_on_page_locked_killable(page);
- if (!PageUptodate(page) && !ret)
- ret = xchg(&desc.ctx->error, 0);
- }
out:
put_nfs_open_context(desc.ctx);
return ret;
--
1.8.3.1