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 <[email protected]>
---
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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