Messages in this thread | | | Date | Wed, 18 May 2022 22:28:33 +0200 | Subject | Re: [PATCH v5 1/3] FUSE: Avoid lookups in fuse create | From | Bernd Schubert <> |
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On 5/18/22 19:44, Vivek Goyal wrote: > On Wed, May 18, 2022 at 01:41:02PM -0400, Vivek Goyal wrote: >> On Tue, May 17, 2022 at 03:37:42PM +0530, Dharmendra Singh wrote: >> >> [..] >>> diff --git a/include/uapi/linux/fuse.h b/include/uapi/linux/fuse.h >>> index d6ccee961891..bebe4be3f1cb 100644 >>> --- a/include/uapi/linux/fuse.h >>> +++ b/include/uapi/linux/fuse.h >>> @@ -301,6 +301,7 @@ struct fuse_file_lock { >>> * FOPEN_CACHE_DIR: allow caching this directory >>> * FOPEN_STREAM: the file is stream-like (no file position at all) >>> * FOPEN_NOFLUSH: don't flush data cache on close (unless FUSE_WRITEBACK_CACHE) >>> + * FOPEN_FILE_CREATED: the file was actually created >>> */ >>> #define FOPEN_DIRECT_IO (1 << 0) >>> #define FOPEN_KEEP_CACHE (1 << 1) >>> @@ -308,6 +309,7 @@ struct fuse_file_lock { >>> #define FOPEN_CACHE_DIR (1 << 3) >>> #define FOPEN_STREAM (1 << 4) >>> #define FOPEN_NOFLUSH (1 << 5) >>> +#define FOPEN_FILE_CREATED (1 << 6) >>> >>> /** >>> * INIT request/reply flags >>> @@ -537,6 +539,7 @@ enum fuse_opcode { >>> FUSE_SETUPMAPPING = 48, >>> FUSE_REMOVEMAPPING = 49, >>> FUSE_SYNCFS = 50, >>> + FUSE_CREATE_EXT = 51, >> >> I am wondering if we really have to introduce a new opcode for this. Both >> FUSE_CREATE and FUSE_CREATE_EXT prepare and send fuse_create_in{} and >> expect fuse_entry_out and fuse_open_out in response. So no new structures >> are being added. Only thing FUSE_CREATE_EXT does extra is that it also >> reports back whether file was actually created or not. >> >> May be instead of adding an new fuse_opcode, we could simply add a >> new flag which we send in fuse_create_in and that reqeusts to report >> if file was created or not. This is along the lines of >> FUSE_OPEN_KILL_SUIDGID. >> >> So say, a new flag FUSE_OPEN_REPORT_CREATE flag. Which we will set in >> fuse_create_in->open_flags. If file server sees this flag is set, it >> knows that it needs to set FOPEN_FILE_CREATED flag in response. >> >> To me creating a new flag FUSE_OPEN_REPORT_CREATE seems better instead >> of adding a new opcode. > > Actually I take that back. If we were to use a flag, then we will have to > do feature negotiation in advance at init time and only then we can set > FUSE_OPEN_REPORT_CREATE. But we are relying on no new feature bit instead > -ENOSYS will be returned if server does not support FUSE_CREATE_EXT. > So adding a new opcode is better.
I guess it might work, if a flag is set and also returned (I would then call it FUSE_CREATE_EXT) - user space creat would need to set FOPEN_FILE_CREATED and that new flag. I just doubt that it simplifies things.
Btw, thanks a lot for your thorough reviews! Much appreciated.
Thanks, Bernd
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