Matthew Wilcox <[email protected]> writes: > On Wed, Nov 12, 2025 at 04:36:05PM +0530, Ojaswin Mujoo wrote: >> From: John Garry <[email protected]> >> >> Add page flag PG_atomic, meaning that a folio needs to be written back >> atomically. This will be used by for handling RWF_ATOMIC buffered IO >> in upcoming patches. > > Page flags are a precious resource. I'm not thrilled about allocating one > to this rather niche usecase. Wouldn't this be more aptly a flag on the > address_space rather than the folio? ie if we're doing this kind of write > to a file, aren't most/all of the writes to the file going to be atomic?
As of today the atomic writes functionality works on the per-write basis (given it's a per-write characteristic). So, we can have two types of dirty folios sitting in the page cache of an inode. Ones which were done using atomic buffered I/O flag (RWF_ATOMIC) and the other ones which were non-atomic writes. Hence a need of a folio flag to distinguish between the two writes. -ritesh
