Sorry for the noise. Ira Weiny had replied my previous mail [1] but unfortunately the reply was moved into junk box, and I didn't note that. [1] https://lore.kernel.org/all/YW2Oj4FrIB8do3zX@xxxxxxxxxx/T/#mb022959fe3b6e9b82e2b066dd8daa301cd2b2c53 On 10/26/21 10:12 PM, JeffleXu wrote: > Hi, > > Recently I'm working on supporting per-file DAX for virtiofs [1]. Vivek > Goyal and I are interested [2] why the default behavior has changed > since introduction of per-file DAX on ext4 and xfs [3][4]. > > That is, before the introduction of per-file DAX, when user doesn't > specify '-o dax', DAX is disabled for all files. After supporting > per-file DAX, when neither '-o dax' nor '-o dax=always|inode|never' is > specified, it actually works in a '-o dax=inode' way if the underlying > blkdev is DAX capable, i.e. depending on the persistent inode flag. That > is, the default behavior has changed from user's perspective. > > We are not sure if this is intentional or not. Appreciate if anyone > could offer some hint. > > > [1] https://lore.kernel.org/all/YW2Oj4FrIB8do3zX@xxxxxxxxxx/T/ > [2] > https://lore.kernel.org/all/YW2Oj4FrIB8do3zX@xxxxxxxxxx/T/#mf067498887ca2023c64c8b8f6aec879557eb28f8 > [3] 9cb20f94afcd2964944f9468e38da736ee855b19 ("fs/ext4: Make DAX mount > option a tri-state") > [4] 02beb2686ff964884756c581d513e103542dcc6a ("fs/xfs: Make DAX mount > option a tri-state") > > -- Thanks, Jeffle
