Julia Lawall <julia.lawall@xxxxxxx> writes: > On Fri, 5 Oct 2018, Kalle Valo wrote: > >> YueHaibing <yuehaibing@xxxxxxxxxx> writes: >> >> > Use DEFINE_DEBUGFS_ATTRIBUTE rather than DEFINE_SIMPLE_ATTRIBUTE >> > for debugfs files. >> > >> > Semantic patch information: >> > Rationale: DEFINE_SIMPLE_ATTRIBUTE + debugfs_create_file() >> > imposes some significant overhead as compared to >> > DEFINE_DEBUGFS_ATTRIBUTE + debugfs_create_file_unsafe(). >> > >> > Generated by: scripts/coccinelle/api/debugfs/debugfs_simple_attr.cocci >> >> Just out of curiosity, what kind of overhead are we talking about here? > > The log message on the commit introducing the semantic patch says the > following: > > In order to protect against file removal races, debugfs files created via > debugfs_create_file() now get wrapped by a struct file_operations at their > opening. > > If the original struct file_operations are known to be safe against removal > races by themselves already, the proxy creation may be bypassed by creating > the files through debugfs_create_file_unsafe(). > > In order to help debugfs users who use the common > DEFINE_SIMPLE_ATTRIBUTE() + debugfs_create_file() > idiom to transition to removal safe struct file_operations, the helper > macro DEFINE_DEBUGFS_ATTRIBUTE() has been introduced. > > Thus, the preferred strategy is to use > DEFINE_DEBUGFS_ATTRIBUTE() + debugfs_create_file_unsafe() > now. I admit that I didn't have time to investigate this is detail but I'm still not understanding where is that "significant overhead" coming from and how big of overhead are we talking about? I guess it has something to do with full_proxy_open() vs open_proxy_open()? Not that I'm against this patch, just curious when I see someone claiming "significant overhead" which is not obvious for me. -- Kalle Valo
