Messages in this thread | | | Date | Fri, 20 Dec 2013 18:54:40 +0400 | From | Maxim Patlasov <> | Subject | Re: [PATCH 07/11] fuse: restructure fuse_readpage() |
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Hi Miklos,
Sorry for delay, see please inline comments below.
On 11/12/2013 09:17 PM, Miklos Szeredi wrote: > On Thu, Oct 10, 2013 at 05:11:25PM +0400, Maxim Patlasov wrote: >> Move the code filling and sending read request to a separate function. Future >> patches will use it for .write_begin -- partial modification of a page >> requires reading the page from the storage very similarly to what fuse_readpage >> does. >> >> Signed-off-by: Maxim Patlasov <MPatlasov@parallels.com> >> --- >> fs/fuse/file.c | 55 +++++++++++++++++++++++++++++++++++++------------------ >> 1 file changed, 37 insertions(+), 18 deletions(-) >> >> diff --git a/fs/fuse/file.c b/fs/fuse/file.c >> index b4d4189..77eb849 100644 >> --- a/fs/fuse/file.c >> +++ b/fs/fuse/file.c >> @@ -700,21 +700,14 @@ static void fuse_short_read(struct fuse_req *req, struct inode *inode, >> } >> } >> >> -static int fuse_readpage(struct file *file, struct page *page) >> +static int __fuse_readpage(struct file *file, struct page *page, size_t count, >> + int *err, struct fuse_req **req_pp, u64 *attr_ver_p) > Signature of this helper looks really ugly. A quick look tells me that neither > caller actually needs 'req'.
fuse_readpage() passes 'req' to fuse_short_read(). And the latter uses req->pages[] to nullify a part of request.
> And fuse_get_attr_version() can be moved to the > one caller that needs it.
Yes, it's doable. But this would make attr_version mechanism less efficient (under some loads): suppose the file on server was truncated externally, then fuse_readpage() acquires fc->attr_version, then some innocent write bumps fc->attr_version while we're waiting for fuse writeback, then fuse_read_update_size() would noop. In the other words, it's beneficial to keep the time interval between acquiring fc->attr_version and subsequent comparison as short as possible.
> And negative err can be returned.
Yes, but this will require some precautions for positive req->out.h.error. Like "err = (req->out.h.error <= 0) ? req->out.h.error : -EIO;". But this must be OK - filtering out positive req->out.h.error is a good idea, imho.
> And then all those > ugly pointer args are gone and the whole thing is much simpler.
If you agree with my comments above, only 1 of 3 ugly pointers can be avoided. Another way would be to revert the code back to the initial implementation where fuse_readpage() and fuse_prepare_write() sent read requests independently.
Thanks, Maxim
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