On Tue, Sep 14, 2021 at 10:13:04AM +1000, NeilBrown wrote: > > Of particular interest is the ext4_journal_start family of calls which > can now have EXT4_EX_NOFAIL 'or'ed in to the 'type'. This could be seen > as a blurring of types. However 'type' is 8 bits, and EXT4_EX_NOFAIL is > a high bit, so it is safe in practice. I'm really not fond of this type blurring. What I'd suggeset doing instead is adding a "gfp_t gfp_mask" parameter to the __ext4_journal_start_sb(). With the exception of one call site in fs/ext4/ialloc.c, most of the callers of __ext4_journal_start_sb() are via #define helper macros or inline funcions. So it would just require adding a GFP_NOFS as an extra parameter to the various macros and inline functions which call __ext4_journal_start_sb() in ext4_jbd2.h. The function ext4_journal_start_with_revoke() is called exactly once so we could just bury the __GFP_NOFAIL in the definition of that macros, e.g.: #define ext4_journal_start_with_revoke(inode, type, blocks, revoke_creds) \ __ext4_journal_start((inode), __LINE__, (type), (blocks), 0, \ GFP_NOFS | __GFP_NOFAIL, (revoke_creds)) but it's probably better to do something like this: #define ext4_journal_start_with_revoke(gfp_mask, inode, type, blocks, revoke_creds) \ __ext4_journal_start((inode), __LINE__, (type), (blocks), 0, \ gfp_mask, (revoke_creds)) So it's explicit in the C function ext4_ext_remove_space() in fs/ext4/extents.c that we are explicitly requesting the __GFP_NOFAIL behavior. Does that make sense? - Ted
