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Subject[PATCH 5/6] FUSE: implement fuse_req->prep()
Date
Implement ->prep() which is the opposite equivalent of ->end().  It's
called right before the request is passed to userland server in the
kernel context of the server. ->prep() can fail the request without
disrupting the whole channel.

This will be used by direct mmap implementation.

Signed-off-by: Tejun Heo <tj@kernel.org>
---
fs/fuse/dev.c | 29 ++++++++++++++++++++++++++---
fs/fuse/fuse_i.h | 6 ++++++
2 files changed, 32 insertions(+), 3 deletions(-)

diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c
index c83ff20..05414b8 100644
--- a/fs/fuse/dev.c
+++ b/fs/fuse/dev.c
@@ -747,6 +747,7 @@ static ssize_t fuse_dev_read(struct kiocb *iocb, const struct iovec *iov,
unsigned long nr_segs, loff_t pos)
{
int err;
+ bool restart;
struct fuse_req *req;
struct fuse_in *in;
struct fuse_copy_state cs;
@@ -793,12 +794,32 @@ static ssize_t fuse_dev_read(struct kiocb *iocb, const struct iovec *iov,
goto restart;
}
spin_unlock(&fc->lock);
+
+ restart = false;
fuse_copy_init(&cs, fc, 1, req, iov, nr_segs);
+
+ /*
+ * Execute prep if available. Failure from prep doesn't
+ * indicate faulty channel. On failure, fail the current
+ * request and proceed to the next one.
+ */
+ if (req->prep) {
+ err = req->prep(fc, req);
+ if (err) {
+ restart = true;
+ goto finish;
+ }
+ }
+
err = fuse_copy_one(&cs, &in->h, sizeof(in->h));
- if (!err)
- err = fuse_copy_args(&cs, in->numargs, in->argpages,
- (struct fuse_arg *) in->args, 0);
+ if (err)
+ goto finish;
+
+ err = fuse_copy_args(&cs, in->numargs, in->argpages,
+ (struct fuse_arg *) in->args, 0);
+ finish:
fuse_copy_finish(&cs);
+
spin_lock(&fc->lock);
req->locked = 0;
if (req->aborted) {
@@ -808,6 +829,8 @@ static ssize_t fuse_dev_read(struct kiocb *iocb, const struct iovec *iov,
if (err) {
req->out.h.error = -EIO;
request_end(fc, req);
+ if (restart)
+ goto restart;
return err;
}
if (!req->isreply)
diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h
index 90eb42c..9d3becb 100644
--- a/fs/fuse/fuse_i.h
+++ b/fs/fuse/fuse_i.h
@@ -282,6 +282,12 @@ struct fuse_req {
/** Link on fi->writepages */
struct list_head writepages_entry;

+ /** Request preparation callback. Called from the kernel
+ context of the FUSE server before passing the request to
+ the FUSE server. Non-zero return from this function will
+ fail the request. */
+ int (*prep)(struct fuse_conn *, struct fuse_req *);
+
/** Request completion callback. This function is called from
the kernel context of the FUSE server if the request isn't
being aborted. If the request is being aborted, it's
--
1.5.6


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