On Mon, Apr 13, 2020 at 9:06 AM <ira.weiny@xxxxxxxxx> wrote: > > From: Ira Weiny <ira.weiny@xxxxxxxxx> > > Add XXX to test per file DAX operations. Please change commit title to "xfs: Add test for per file DAX operations" The title Add xfs/XXX is not useful even if XXX where a number. But the kernel patch suggests that there is an intention to make this behavior also applicable to ext4?? If that is the case I would recommend making this a generic tests which requires filesystem support for -o dax=XXX > > The following is tested[*] > > 1. There exists an in-kernel access mode flag S_DAX that is set when > file accesses go directly to persistent memory, bypassing the page > cache. Applications must call statx to discover the current S_DAX > state (STATX_ATTR_DAX). > > 2. There exists an advisory file inode flag FS_XFLAG_DAX that is > inherited from the parent directory FS_XFLAG_DAX inode flag at file > creation time. This advisory flag can be set or cleared at any > time, but doing so does not immediately affect the S_DAX state. > > Unless overridden by mount options (see (3)), if FS_XFLAG_DAX is set > and the fs is on pmem then it will enable S_DAX at inode load time; > if FS_XFLAG_DAX is not set, it will not enable S_DAX. > > 3. There exists a dax= mount option. > > "-o dax=never" means "never set S_DAX, ignore FS_XFLAG_DAX." > > "-o dax=always" means "always set S_DAX (at least on pmem), > and ignore FS_XFLAG_DAX." > > "-o dax" is an alias for "dax=always". > > "-o dax=inode" means "follow FS_XFLAG_DAX" and is the default. > > 4. There exists an advisory directory inode flag FS_XFLAG_DAX that can > be set or cleared at any time. The flag state is copied into any > files or subdirectories when they are created within that directory. > > 5. Programs that require a specific file access mode (DAX or not DAX) > can do one of the following: > > (a) Create files in directories that the FS_XFLAG_DAX flag set as > needed; or > > (b) Have the administrator set an override via mount option; or > > (c) Set or clear the file's FS_XFLAG_DAX flag as needed. Programs > must then cause the kernel to evict the inode from memory. This > can be done by: > > i> Closing the file and re-opening the file and using statx to > see if the fs has changed the S_DAX flag; and > > ii> If the file still does not have the desired S_DAX access > mode, either unmount and remount the filesystem, or close > the file and use drop_caches. > > 6. It's not unreasonable that users who want to squeeze every last bit > of performance out of the particular rough and tumble bits of their > storage also be exposed to the difficulties of what happens when the > operating system can't totally virtualize those hardware > capabilities. Your high performance sports car is not a Toyota > minivan, as it were. > > [*] https://lore.kernel.org/lkml/20200409165927.GD6741@magnolia/ > > Signed-off-by: Ira Weiny <ira.weiny@xxxxxxxxx> > > --- > Changes from v6 (kernel patch set): > Start versions tracking the kernel patch set. > Update for new requirements > > Changes from V1 (xfstests patch): > Add test to ensure moved files preserve their flag > Check chattr of non-dax flags (check bug found by Darrick) > --- ... > --- a/tests/xfs/group > +++ b/tests/xfs/group > @@ -511,3 +511,4 @@ > 511 auto quick quota > 512 auto quick acl attr > 513 auto mount > +999 auto The test looks also 'quick' Thanks, Amir.
