On Wed, Feb 26, 2020 at 05:05:03AM -0800, Matthew Wilcox wrote: > On Wed, Feb 26, 2020 at 03:27:08PM +0530, Ritesh Harjani wrote: > > Currently FIEMAP_EXTENT_LAST is not working consistently across > > different filesystem's fiemap implementations and thus this feature > > may be broken. So fix the documentation about this flag to meet the > > right expectations. > > Are you saying filesystems have both false positives and false negatives? > I can understand how a filesystem might fail to set FIEMAP_EXTENT_LAST, > but not how a filesystem might set it when there's actually another > extent beyond this one. > > > * FIEMAP_EXTENT_LAST > > -This is the last extent in the file. A mapping attempt past this > > -extent will return nothing. > > +This is generally the last extent in the file. A mapping attempt past this > > +extent may return nothing. But the user must still confirm by trying to map > > +past this extent, since different filesystems implement this differently. "This flag means nothing and can be set arbitrarily by the fs for the lulz." Yuck. I was really hoping for "This is set on the last extent record in the dataset generated by the query parameters", particularly becaue that's how e2fsprogs utilties interpret that flag. --D
