On Sat, Jul 5, 2025 at 2:06 AM John Groves <John@xxxxxxxxxx> wrote: > > On 25/07/04 03:30PM, John Groves wrote: > > On 25/07/04 10:54AM, Amir Goldstein wrote: > > > On Thu, Jul 3, 2025 at 8:51 PM John Groves <John@xxxxxxxxxx> wrote: > > > > > > > > Upon completion of an OPEN, if we're in famfs-mode we do a GET_FMAP to > > > > retrieve and cache up the file-to-dax map in the kernel. If this > > > > succeeds, read/write/mmap are resolved direct-to-dax with no upcalls. > > > > > > > > GET_FMAP has a variable-size response payload, and the allocated size > > > > is sent in the in_args[0].size field. If the fmap would overflow the > > > > message, the fuse server sends a reply of size 'sizeof(uint32_t)' which > > > > specifies the size of the fmap message. Then the kernel can realloc a > > > > large enough buffer and try again. > > > > > > > > Signed-off-by: John Groves <john@xxxxxxxxxx> > > > > --- > > > > fs/fuse/file.c | 84 +++++++++++++++++++++++++++++++++++++++ > > > > fs/fuse/fuse_i.h | 36 ++++++++++++++++- > > > > fs/fuse/inode.c | 19 +++++++-- > > > > fs/fuse/iomode.c | 2 +- > > > > include/uapi/linux/fuse.h | 18 +++++++++ > > > > 5 files changed, 154 insertions(+), 5 deletions(-) > > > > > > > > diff --git a/fs/fuse/file.c b/fs/fuse/file.c > > > > index 93b82660f0c8..8616fb0a6d61 100644 > > > > --- a/fs/fuse/file.c > > > > +++ b/fs/fuse/file.c > > > > @@ -230,6 +230,77 @@ static void fuse_truncate_update_attr(struct inode *inode, struct file *file) > > > > fuse_invalidate_attr_mask(inode, FUSE_STATX_MODSIZE); > > > > } > > > > > > > > +#if IS_ENABLED(CONFIG_FUSE_FAMFS_DAX) > > > > > > We generally try to avoid #ifdef blocks in c files > > > keep them mostly in h files and use in c files > > > if (IS_ENABLED(CONFIG_FUSE_FAMFS_DAX)) > > > > > > also #if IS_ENABLED(CONFIG_FUSE_FAMFS_DAX) > > > it a bit strange for a bool Kconfig because it looks too > > > much like the c code, so I prefer > > > #ifdef CONFIG_FUSE_FAMFS_DAX > > > when you have to use it > > > > > > If you need entire functions compiled out, why not put them in famfs.c? > > > > Perhaps moving fuse_get_fmap() to famfs.c is the best approach. Will try that > > first. > > > > Regarding '#if IS_ENABLED(CONFIG_FUSE_FAMFS_DAX)', vs. > > '#ifdef CONFIG_FUSE_FAMFS_DAX' vs. '#if CONFIG_FUSE_FAMFS_DAX'... > > > > I've learned to be cautious there because the latter two are undefined if > > CONFIG_FUSE_FAMFS_DAX=m. I've been burned by this. Yes, that's a risk, but as the code is shaping up right now, I do not foresee FAMFS becoming a module(?) > > > > My original thinking was that famfs made sense as a module, but I'm leaning > > the other way now - and in this series fs/fuse/Kconfig makes it a bool - > > meaning all three macro tests will work because a bool can't be set to 'm'. > > > > So to the extent that I need conditional compilation macros I can switch > > to '#ifdef...'. > > Doh. Spirit of full disclosure: this commit doesn't build if > CONFIG_FUSE_FAMFS_DAX is not set (!=y). So the conditionals are at > risk if getting worse, not better. Working on it... > You're probably going to need to add stub inline functions for all the functions from famfs.c and a few more wrappers I guess. The right amount of ifdefs in C files is really a matter of judgement, but the fewer the better for code flow clarity. Thanks, Amir.
