user/sven/linux.git/include/linux/buffer_head.h, branch v5.19.16

fs: only do a memory barrier for the first set_buffer_uptodate()

2022-09-15T08:47:07Z

commit 2f79cdfe58c13949bbbb65ba5926abfe9561d0ec upstream. Commit d4252071b97d ("add barriers to buffer_uptodate and set_buffer_uptodate") added proper memory barriers to the buffer head BH_Uptodate bit, so that anybody who tests a buffer for being up-to-date will be guaranteed to actually see initialized state. However, that commit didn't _just_ add the memory barrier, it also ended up dropping the "was it already set" logic that the BUFFER_FNS() macro had. That's conceptually the right thing for a generic "this is a memory barrier" operation, but in the case of the buffer contents, we really only care about the memory barrier for the _first_ time we set the bit, in that the only memory ordering protection we need is to avoid anybody seeing uninitialized memory contents. Any other access ordering wouldn't be about the BH_Uptodate bit anyway, and would require some other proper lock (typically BH_Lock or the folio lock). A reader that races with somebody invalidating the buffer head isn't an issue wrt the memory ordering, it's a serialization issue. Now, you'd think that the buffer head operations don't matter in this day and age (and I certainly thought so), but apparently some loads still end up being heavy users of buffer heads. In particular, the kernel test robot reported that not having this bit access optimization in place caused a noticeable direct IO performance regression on ext4: fxmark.ssd_ext4_no_jnl_DWTL_54_directio.works/sec -26.5% regression although you presumably need a fast disk and a lot of cores to actually notice. Link: https://lore.kernel.org/all/Yw8L7HTZ%2FdE2%2Fo9C@xsang-OptiPlex-9020/ Reported-by: kernel test robot Tested-by: Fengwei Yin Cc: Mikulas Patocka Cc: Matthew Wilcox (Oracle) Cc: stable@kernel.org Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman

add barriers to buffer_uptodate and set_buffer_uptodate

2022-08-17T13:13:41Z

commit d4252071b97d2027d246f6a82cbee4d52f618b47 upstream. Let's have a look at this piece of code in __bread_slow: get_bh(bh); bh->b_end_io = end_buffer_read_sync; submit_bh(REQ_OP_READ, 0, bh); wait_on_buffer(bh); if (buffer_uptodate(bh)) return bh; Neither wait_on_buffer nor buffer_uptodate contain any memory barrier. Consequently, if someone calls sb_bread and then reads the buffer data, the read of buffer data may be executed before wait_on_buffer(bh) on architectures with weak memory ordering and it may return invalid data. Fix this bug by adding a memory barrier to set_buffer_uptodate and an acquire barrier to buffer_uptodate (in a similar way as folio_test_uptodate and folio_mark_uptodate). Signed-off-by: Mikulas Patocka Reviewed-by: Matthew Wilcox (Oracle) Cc: stable@vger.kernel.org Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman

fs: Change try_to_free_buffers() to take a folio

2022-05-10T03:12:34Z

All but two of the callers already have a folio; pass a folio into try_to_free_buffers(). This removes the last user of cancel_dirty_page() so remove that wrapper function too. Signed-off-by: Matthew Wilcox (Oracle) Reviewed-by: Jeff Layton

fs: Convert block_read_full_page() to block_read_full_folio()

2022-05-09T20:21:44Z

This function is NOT converted to handle large folios, so include an assert that the filesystem isn't passing one in. Otherwise, use the folio functions instead of the page functions, where they exist. Convert all filesystems which use block_read_full_page(). Signed-off-by: Matthew Wilcox (Oracle)

fs: Convert is_dirty_writeback() to take a folio

2022-05-08T18:45:56Z

Pass a folio instead of a page to aops->is_dirty_writeback(). Convert both implementations and the caller. Signed-off-by: Matthew Wilcox (Oracle) Reviewed-by: Christoph Hellwig

fs: Remove aop flags parameter from nobh_write_begin()

2022-05-08T18:28:19Z

There are no more aop flags left, so remove the parameter. Signed-off-by: Matthew Wilcox (Oracle) Reviewed-by: Christoph Hellwig

fs: Remove aop flags parameter from cont_write_begin()

2022-05-08T18:28:19Z

There are no more aop flags left, so remove the parameter. Signed-off-by: Matthew Wilcox (Oracle) Reviewed-by: Christoph Hellwig

fs: Remove aop flags parameter from block_write_begin()

2022-05-08T18:28:19Z

There are no more aop flags left, so remove the parameter. Signed-off-by: Matthew Wilcox (Oracle) Reviewed-by: Christoph Hellwig

fs: Convert __set_page_dirty_buffers to block_dirty_folio

2022-03-16T17:37:04Z

Convert all callers; mostly this is just changing the aops to point at it, but a few implementations need a little more work. Signed-off-by: Matthew Wilcox (Oracle) Tested-by: Damien Le Moal Acked-by: Damien Le Moal Tested-by: Mike Marshall # orangefs Tested-by: David Howells # afs

fs: Turn block_invalidatepage into block_invalidate_folio

2022-03-15T12:23:29Z

Remove special-casing of a NULL invalidatepage, since there is no more block_invalidatepage. Signed-off-by: Matthew Wilcox (Oracle) Tested-by: Damien Le Moal Acked-by: Damien Le Moal Tested-by: Mike Marshall # orangefs Tested-by: David Howells # afs