Messages in this thread | | | Subject | Re: [patch 12/12] fuse: add blksize field to fuse_attr | From | Miklos Szeredi <> | Date | Fri, 05 Oct 2007 01:15:05 +0200 |
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> > From: Miklos Szeredi <mszeredi@suse.cz> > > > > Allow the userspace filesystem to supply a blksize value to be > > returned by stat() and friends. If the field is zero, it defaults to > > the old PAGE_CACHE_SIZE value. > > > > Why does fuse need this feature?
There are cases, when the filesystem will be passed the buffer from a single read or write call, namely:
1) in 'direct-io' mode (not O_DIRECT), read/write requests don't go through the page cache, but go directly to the userspace fs
2) currently buffered writes are done with single page requests, but if Nick's ->perform_write() patch goes it, it will be possible to do larger write requests. But only if the original write() was also bigger than a page.
In these cases the filesystem might want to give a hint to the app about the optimal I/O size.
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