6.10-stable review patch. If anyone has any objections, please let me know.
------------------
From: Naohiro Aota naohiro.aota@wdc.com
[ Upstream commit 6252690f7e1b173b86a4c27dfc046b351ab423e7 ]
In __extent_writepage_io(), we call btrfs_set_range_writeback() -> folio_start_writeback(), which clears PAGECACHE_TAG_DIRTY mark from the mapping xarray if the folio is not dirty. This worked fine before commit 97713b1a2ced ("btrfs: do not clear page dirty inside extent_write_locked_range()").
After the commit, however, the folio is still dirty at this point, so the mapping DIRTY tag is not cleared anymore. Then, __extent_writepage_io() calls btrfs_folio_clear_dirty() to clear the folio's dirty flag. That results in the page being unlocked with a "strange" state. The page is not PageDirty, but the mapping tag is set as PAGECACHE_TAG_DIRTY.
This strange state looks like causing a hang with a call trace below when running fstests generic/091 on a null_blk device. It is waiting for a folio lock.
While I don't have an exact relation between this hang and the strange state, fixing the state also fixes the hang. And, that state is worth fixing anyway.
This commit reorders btrfs_folio_clear_dirty() and btrfs_set_range_writeback() in __extent_writepage_io(), so that the PAGECACHE_TAG_DIRTY tag is properly removed from the xarray.
[464.274] task:fsx state:D stack:0 pid:3034 tgid:3034 ppid:2853 flags:0x00004002 [464.286] Call Trace: [464.291] <TASK> [464.295] __schedule+0x10ed/0x6260 [464.301] ? __pfx___blk_flush_plug+0x10/0x10 [464.308] ? __submit_bio+0x37c/0x450 [464.314] ? __pfx___schedule+0x10/0x10 [464.321] ? lock_release+0x567/0x790 [464.327] ? __pfx_lock_acquire+0x10/0x10 [464.334] ? __pfx_lock_release+0x10/0x10 [464.340] ? __pfx_lock_acquire+0x10/0x10 [464.347] ? __pfx_lock_release+0x10/0x10 [464.353] ? do_raw_spin_lock+0x12e/0x270 [464.360] schedule+0xdf/0x3b0 [464.365] io_schedule+0x8f/0xf0 [464.371] folio_wait_bit_common+0x2ca/0x6d0 [464.378] ? folio_wait_bit_common+0x1cc/0x6d0 [464.385] ? __pfx_folio_wait_bit_common+0x10/0x10 [464.392] ? __pfx_filemap_get_folios_tag+0x10/0x10 [464.400] ? __pfx_wake_page_function+0x10/0x10 [464.407] ? __pfx___might_resched+0x10/0x10 [464.414] ? do_raw_spin_unlock+0x58/0x1f0 [464.420] extent_write_cache_pages+0xe49/0x1620 [btrfs] [464.428] ? lock_acquire+0x435/0x500 [464.435] ? __pfx_extent_write_cache_pages+0x10/0x10 [btrfs] [464.443] ? btrfs_do_write_iter+0x493/0x640 [btrfs] [464.451] ? orc_find.part.0+0x1d4/0x380 [464.457] ? __pfx_lock_release+0x10/0x10 [464.464] ? __pfx_lock_release+0x10/0x10 [464.471] ? btrfs_do_write_iter+0x493/0x640 [btrfs] [464.478] btrfs_writepages+0x1cc/0x460 [btrfs] [464.485] ? __pfx_btrfs_writepages+0x10/0x10 [btrfs] [464.493] ? is_bpf_text_address+0x6e/0x100 [464.500] ? kernel_text_address+0x145/0x160 [464.507] ? unwind_get_return_address+0x5e/0xa0 [464.514] ? arch_stack_walk+0xac/0x100 [464.521] do_writepages+0x176/0x780 [464.527] ? lock_release+0x567/0x790 [464.533] ? __pfx_do_writepages+0x10/0x10 [464.540] ? __pfx_lock_acquire+0x10/0x10 [464.546] ? __pfx_stack_trace_save+0x10/0x10 [464.553] ? do_raw_spin_lock+0x12e/0x270 [464.560] ? do_raw_spin_unlock+0x58/0x1f0 [464.566] ? _raw_spin_unlock+0x23/0x40 [464.573] ? wbc_attach_and_unlock_inode+0x3da/0x7d0 [464.580] filemap_fdatawrite_wbc+0x113/0x180 [464.587] ? prepare_pages.constprop.0+0x13c/0x5c0 [btrfs] [464.596] __filemap_fdatawrite_range+0xaf/0xf0 [464.603] ? __pfx___filemap_fdatawrite_range+0x10/0x10 [464.611] ? trace_irq_enable.constprop.0+0xce/0x110 [464.618] ? kasan_quarantine_put+0xd7/0x1e0 [464.625] btrfs_start_ordered_extent+0x46f/0x570 [btrfs] [464.633] ? __pfx_btrfs_start_ordered_extent+0x10/0x10 [btrfs] [464.642] ? __clear_extent_bit+0x2c0/0x9d0 [btrfs] [464.650] btrfs_lock_and_flush_ordered_range+0xc6/0x180 [btrfs] [464.659] ? __pfx_btrfs_lock_and_flush_ordered_range+0x10/0x10 [btrfs] [464.669] btrfs_read_folio+0x12a/0x1d0 [btrfs] [464.676] ? __pfx_btrfs_read_folio+0x10/0x10 [btrfs] [464.684] ? __pfx_filemap_add_folio+0x10/0x10 [464.691] ? __pfx___might_resched+0x10/0x10 [464.698] ? __filemap_get_folio+0x1c5/0x450 [464.705] prepare_uptodate_page+0x12e/0x4d0 [btrfs] [464.713] prepare_pages.constprop.0+0x13c/0x5c0 [btrfs] [464.721] ? fault_in_iov_iter_readable+0xd2/0x240 [464.729] btrfs_buffered_write+0x5bd/0x12f0 [btrfs] [464.737] ? __pfx_btrfs_buffered_write+0x10/0x10 [btrfs] [464.745] ? __pfx_lock_release+0x10/0x10 [464.752] ? generic_write_checks+0x275/0x400 [464.759] ? down_write+0x118/0x1f0 [464.765] ? up_write+0x19b/0x500 [464.770] btrfs_direct_write+0x731/0xba0 [btrfs] [464.778] ? __pfx_btrfs_direct_write+0x10/0x10 [btrfs] [464.785] ? __pfx___might_resched+0x10/0x10 [464.792] ? lock_acquire+0x435/0x500 [464.798] ? lock_acquire+0x435/0x500 [464.804] btrfs_do_write_iter+0x494/0x640 [btrfs] [464.811] ? __pfx_btrfs_do_write_iter+0x10/0x10 [btrfs] [464.819] ? __pfx___might_resched+0x10/0x10 [464.825] ? rw_verify_area+0x6d/0x590 [464.831] vfs_write+0x5d7/0xf50 [464.837] ? __might_fault+0x9d/0x120 [464.843] ? __pfx_vfs_write+0x10/0x10 [464.849] ? btrfs_file_llseek+0xb1/0xfb0 [btrfs] [464.856] ? lock_release+0x567/0x790 [464.862] ksys_write+0xfb/0x1d0 [464.867] ? __pfx_ksys_write+0x10/0x10 [464.873] ? _raw_spin_unlock+0x23/0x40 [464.879] ? btrfs_getattr+0x4af/0x670 [btrfs] [464.886] ? vfs_getattr_nosec+0x79/0x340 [464.892] do_syscall_64+0x95/0x180 [464.898] ? __do_sys_newfstat+0xde/0xf0 [464.904] ? __pfx___do_sys_newfstat+0x10/0x10 [464.911] ? trace_irq_enable.constprop.0+0xce/0x110 [464.918] ? syscall_exit_to_user_mode+0xac/0x2a0 [464.925] ? do_syscall_64+0xa1/0x180 [464.931] ? trace_irq_enable.constprop.0+0xce/0x110 [464.939] ? trace_irq_enable.constprop.0+0xce/0x110 [464.946] ? syscall_exit_to_user_mode+0xac/0x2a0 [464.953] ? btrfs_file_llseek+0xb1/0xfb0 [btrfs] [464.960] ? do_syscall_64+0xa1/0x180 [464.966] ? btrfs_file_llseek+0xb1/0xfb0 [btrfs] [464.973] ? trace_irq_enable.constprop.0+0xce/0x110 [464.980] ? syscall_exit_to_user_mode+0xac/0x2a0 [464.987] ? __pfx_btrfs_file_llseek+0x10/0x10 [btrfs] [464.995] ? trace_irq_enable.constprop.0+0xce/0x110 [465.002] ? __pfx_btrfs_file_llseek+0x10/0x10 [btrfs] [465.010] ? do_syscall_64+0xa1/0x180 [465.016] ? lock_release+0x567/0x790 [465.022] ? __pfx_lock_acquire+0x10/0x10 [465.028] ? __pfx_lock_release+0x10/0x10 [465.034] ? trace_irq_enable.constprop.0+0xce/0x110 [465.042] ? syscall_exit_to_user_mode+0xac/0x2a0 [465.049] ? do_syscall_64+0xa1/0x180 [465.055] ? syscall_exit_to_user_mode+0xac/0x2a0 [465.062] ? do_syscall_64+0xa1/0x180 [465.068] ? syscall_exit_to_user_mode+0xac/0x2a0 [465.075] ? do_syscall_64+0xa1/0x180 [465.081] ? clear_bhb_loop+0x25/0x80 [465.087] ? clear_bhb_loop+0x25/0x80 [465.093] ? clear_bhb_loop+0x25/0x80 [465.099] entry_SYSCALL_64_after_hwframe+0x76/0x7e [465.106] RIP: 0033:0x7f093b8ee784 [465.111] RSP: 002b:00007ffc29d31b28 EFLAGS: 00000202 ORIG_RAX: 0000000000000001 [465.122] RAX: ffffffffffffffda RBX: 0000000000006000 RCX: 00007f093b8ee784 [465.131] RDX: 000000000001de00 RSI: 00007f093b6ed200 RDI: 0000000000000003 [465.141] RBP: 000000000001de00 R08: 0000000000006000 R09: 0000000000000000 [465.150] R10: 0000000000023e00 R11: 0000000000000202 R12: 0000000000006000 [465.160] R13: 0000000000023e00 R14: 0000000000023e00 R15: 0000000000000001 [465.170] </TASK> [465.174] INFO: lockdep is turned off.
Reported-by: Shinichiro Kawasaki shinichiro.kawasaki@wdc.com Fixes: 97713b1a2ced ("btrfs: do not clear page dirty inside extent_write_locked_range()") Reviewed-by: Qu Wenruo wqu@suse.com Signed-off-by: Naohiro Aota naohiro.aota@wdc.com Signed-off-by: David Sterba dsterba@suse.com Signed-off-by: Sasha Levin sashal@kernel.org --- fs/btrfs/extent_io.c | 14 +++++++------- 1 file changed, 7 insertions(+), 7 deletions(-)
diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c index 0486b1f911248..3bad7c0be1f10 100644 --- a/fs/btrfs/extent_io.c +++ b/fs/btrfs/extent_io.c @@ -1420,6 +1420,13 @@ static noinline_for_stack int __extent_writepage_io(struct btrfs_inode *inode, free_extent_map(em); em = NULL;
+ /* + * Although the PageDirty bit might be cleared before entering + * this function, subpage dirty bit is not cleared. + * So clear subpage dirty bit here so next time we won't submit + * page for range already written to disk. + */ + btrfs_folio_clear_dirty(fs_info, page_folio(page), cur, iosize); btrfs_set_range_writeback(inode, cur, cur + iosize - 1); if (!PageWriteback(page)) { btrfs_err(inode->root->fs_info, @@ -1427,13 +1434,6 @@ static noinline_for_stack int __extent_writepage_io(struct btrfs_inode *inode, page->index, cur, end); }
- /* - * Although the PageDirty bit is cleared before entering this - * function, subpage dirty bit is not cleared. - * So clear subpage dirty bit here so next time we won't submit - * page for range already written to disk. - */ - btrfs_folio_clear_dirty(fs_info, page_folio(page), cur, iosize);
submit_extent_page(bio_ctrl, disk_bytenr, page, iosize, cur - page_offset(page));