On Mon, Mar 21, 2011 at 4:43 AM, Ted Ts'o <tytso@xxxxxxx> wrote: > On Tue, Mar 01, 2011 at 03:30:24PM +0200, Amir Goldstein wrote: >> ext4_handle_release_buffer() is an API, which is not being used properly. >> This is not so bad considering that it calls jbd2_journal_release_buffer(), >> which does nothing, but the snapshots implementation of this API does >> something. >> >> ext4_jbd2.h defines 2 identical wrapper functions: >> ext4_journal_release_buffer() and ext4_handle_release_buffer(). >> The former has no callers, so it was removed. > > Note that there are some commented-out calls to > ext4_journal_release_buffer() in resize.c; they're probably commented > out because at least today, jbd2_journal_release_buffer() is indeed a > no-op. > > I'll update resize.c to use the preferred call. Speaking of which, > how does on-line resize work in the face of the snapshot feature? Is > that something that is or isn't supported? Yes, it is supported. (offline resize isn't supported). The old snapshots sizes (i_disksize) represent the file system size at the time of the snapshot. > > Note also that there may be places where a buffer has > get_write_access() called on it, only for it to be never modified. > resize.c is an example of that. Those places can be a problem (since COW does happen and use up transaction credits) and calling buffer_release can help (it tries to extend the transaction), but specifically, resize.c is not a problem, since blocks outside the active snapshot's i_disksize are never COWed. > >> There are 2 users of the API: >> ext4_new_inode() calls ext4_handle_release_buffer() and >> ext4_xattr_block_set() calls jbd2_journal_release_buffer() directly. >> The latter was chagned to call the wrapper API. >> >> Signed-off-by: Amir Goldstein <amir73il@xxxxxxxxxxxx> > > I'll apply this patch the changes. > > - Ted > > -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
