| Message ID | 1679653680-2-1-git-send-email-ruansy.fnst@fujitsu.com (mailing list archive) |
|---|---|
| State | Mainlined, archived |
| Headers | show |
| Series | fsdax: force clear dirty mark if CoW | expand |
On Fri, 24 Mar 2023 10:28:00 +0000 Shiyang Ruan <ruansy.fnst@fujitsu.com> wrote: > XFS allows CoW on non-shared extents to combat fragmentation[1]. The > old non-shared extent could be mwrited before, its dax entry is marked > dirty. To be able to delete this entry, clear its dirty mark before > invalidate_inode_pages2_range(). What are the user-visible runtime effects of this flaw? Are we able to identify a Fixes: target for this? Perhaps f80e1668888f3 ("fsdax: invalidate pages when CoW")?
在 2023/3/25 3:42, Andrew Morton 写道: > On Fri, 24 Mar 2023 10:28:00 +0000 Shiyang Ruan <ruansy.fnst@fujitsu.com> wrote: > >> XFS allows CoW on non-shared extents to combat fragmentation[1]. The >> old non-shared extent could be mwrited before, its dax entry is marked >> dirty. To be able to delete this entry, clear its dirty mark before >> invalidate_inode_pages2_range(). > > What are the user-visible runtime effects of this flaw? This bug won't leak or mess up the data of filesystem. In dmesg it will show like this: [ 28.512349] ------------[ cut here ]------------ [ 28.512622] WARNING: CPU: 2 PID: 5255 at fs/dax.c:390 dax_insert_entry+0x342/0x390 [ 28.513050] Modules linked in: rpcsec_gss_krb5 auth_rpcgss nfsv4 nfs lockd grace fscache netfs nft_fib_inet nft_fib_ipv4 nft_fib_ipv6 nft_fib nft_reject_inet nf_reject_ipv4 nf_reject_ipv6 nft_reject nft_ct nf_conntrack nf_defrag_ipv6 nf_defrag_ipv4 ip_set nf_tables [ 28.515462] CPU: 2 PID: 5255 Comm: fsstress Kdump: loaded Not tainted 6.3.0-rc1-00001-g85e1481e19c1-dirty #117 [ 28.515902] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS Arch Linux 1.16.1-1-1 04/01/2014 [ 28.516307] RIP: 0010:dax_insert_entry+0x342/0x390 [ 28.516536] Code: 30 5b 5d 41 5c 41 5d 41 5e 41 5f c3 cc cc cc cc 48 8b 45 20 48 83 c0 01 e9 e2 fe ff ff 48 8b 45 20 48 83 c0 01 e9 cd fe ff ff <0f> 0b e9 53 ff ff ff 48 8b 7c 24 08 31 f6 e8 1b 61 a1 00 eb 8c 48 [ 28.517417] RSP: 0000:ffffc9000845fb18 EFLAGS: 00010086 [ 28.517721] RAX: 0000000000000053 RBX: 0000000000000155 RCX: 000000000018824b [ 28.518113] RDX: 0000000000000000 RSI: ffffffff827525a6 RDI: 00000000ffffffff [ 28.518515] RBP: ffffea00062092c0 R08: 0000000000000000 R09: ffffc9000845f9c8 [ 28.518905] R10: 0000000000000003 R11: ffffffff82ddb7e8 R12: 0000000000000155 [ 28.519301] R13: 0000000000000000 R14: 000000000018824b R15: ffff88810cfa76b8 [ 28.519703] FS: 00007f14a0c94740(0000) GS:ffff88817bd00000(0000) knlGS:0000000000000000 [ 28.520148] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 28.520472] CR2: 00007f14a0c8d000 CR3: 000000010321c004 CR4: 0000000000770ee0 [ 28.520863] PKRU: 55555554 [ 28.521043] Call Trace: [ 28.521219] <TASK> [ 28.521368] dax_fault_iter+0x196/0x390 [ 28.521595] dax_iomap_pte_fault+0x19b/0x3d0 [ 28.521852] __xfs_filemap_fault+0x234/0x2b0 [ 28.522116] __do_fault+0x30/0x130 [ 28.522334] do_fault+0x193/0x340 [ 28.522586] __handle_mm_fault+0x2d3/0x690 [ 28.522975] handle_mm_fault+0xe6/0x2c0 [ 28.523259] do_user_addr_fault+0x1bc/0x6f0 [ 28.523521] exc_page_fault+0x60/0x140 [ 28.523763] asm_exc_page_fault+0x22/0x30 [ 28.524001] RIP: 0033:0x7f14a0b589ca [ 28.524225] Code: c5 fe 7f 07 c5 fe 7f 47 20 c5 fe 7f 47 40 c5 fe 7f 47 60 c5 f8 77 c3 66 0f 1f 84 00 00 00 00 00 40 0f b6 c6 48 89 d1 48 89 fa <f3> aa 48 89 d0 c5 f8 77 c3 66 66 2e 0f 1f 84 00 00 00 00 00 66 90 [ 28.525198] RSP: 002b:00007fff1dea1c98 EFLAGS: 00010202 [ 28.525505] RAX: 000000000000001e RBX: 000000000014a000 RCX: 0000000000006046 [ 28.525895] RDX: 00007f14a0c82000 RSI: 000000000000001e RDI: 00007f14a0c8d000 [ 28.526290] RBP: 000000000000006f R08: 0000000000000004 R09: 000000000014a000 [ 28.526681] R10: 0000000000000008 R11: 0000000000000246 R12: 028f5c28f5c28f5c [ 28.527067] R13: 8f5c28f5c28f5c29 R14: 0000000000011046 R15: 00007f14a0c946c0 [ 28.527449] </TASK> [ 28.527600] ---[ end trace 0000000000000000 ]--- > > Are we able to identify a Fixes: target for this? Perhaps > f80e1668888f3 ("fsdax: invalidate pages when CoW")? > Yes, it is to fix this commit. -- Thanks, Ruan.
On Mon, 27 Mar 2023 11:19:01 +0800 Shiyang Ruan <ruansy.fnst@fujitsu.com> wrote: > > > 在 2023/3/25 3:42, Andrew Morton 写道: > > On Fri, 24 Mar 2023 10:28:00 +0000 Shiyang Ruan <ruansy.fnst@fujitsu.com> wrote: > > > >> XFS allows CoW on non-shared extents to combat fragmentation[1]. The > >> old non-shared extent could be mwrited before, its dax entry is marked > >> dirty. To be able to delete this entry, clear its dirty mark before > >> invalidate_inode_pages2_range(). > > > > What are the user-visible runtime effects of this flaw? > > This bug won't leak or mess up the data of filesystem. In dmesg it will > show like this: > > [ 28.512349] ------------[ cut here ]------------ > [ 28.512622] WARNING: CPU: 2 PID: 5255 at fs/dax.c:390 > dax_insert_entry+0x342/0x390 > > ... > > > > > Are we able to identify a Fixes: target for this? Perhaps > > f80e1668888f3 ("fsdax: invalidate pages when CoW")? > > > > Yes, it is to fix this commit. OK, thanks. I added the extra changelog info, added the Fixes and a cc:stable. Some review from other fsdax developers would be helpful, please.
diff --git a/fs/dax.c b/fs/dax.c index 5d2e9b10030e..2ababb89918d 100644 --- a/fs/dax.c +++ b/fs/dax.c @@ -781,6 +781,33 @@ static int __dax_invalidate_entry(struct address_space *mapping, return ret; } +static int __dax_clear_dirty_range(struct address_space *mapping, + pgoff_t start, pgoff_t end) +{ + XA_STATE(xas, &mapping->i_pages, start); + unsigned int scanned = 0; + void *entry; + + xas_lock_irq(&xas); + xas_for_each(&xas, entry, end) { + entry = get_unlocked_entry(&xas, 0); + xas_clear_mark(&xas, PAGECACHE_TAG_DIRTY); + xas_clear_mark(&xas, PAGECACHE_TAG_TOWRITE); + put_unlocked_entry(&xas, entry, WAKE_NEXT); + + if (++scanned % XA_CHECK_SCHED) + continue; + + xas_pause(&xas); + xas_unlock_irq(&xas); + cond_resched(); + xas_lock_irq(&xas); + } + xas_unlock_irq(&xas); + + return 0; +} + /* * Delete DAX entry at @index from @mapping. Wait for it * to be unlocked before deleting it. @@ -1440,6 +1467,16 @@ static loff_t dax_iomap_iter(const struct iomap_iter *iomi, * written by write(2) is visible in mmap. */ if (iomap->flags & IOMAP_F_NEW || cow) { + /* + * Filesystem allows CoW on non-shared extents. The src extents + * may have been mmapped with dirty mark before. To be able to + * invalidate its dax entries, we need to clear the dirty mark + * in advance. + */ + if (cow) + __dax_clear_dirty_range(iomi->inode->i_mapping, + pos >> PAGE_SHIFT, + (end - 1) >> PAGE_SHIFT); invalidate_inode_pages2_range(iomi->inode->i_mapping, pos >> PAGE_SHIFT, (end - 1) >> PAGE_SHIFT);
XFS allows CoW on non-shared extents to combat fragmentation[1]. The old non-shared extent could be mwrited before, its dax entry is marked dirty. To be able to delete this entry, clear its dirty mark before invalidate_inode_pages2_range(). [1] https://lore.kernel.org/linux-xfs/20230321151339.GA11376@frogsfrogsfrogs/ Signed-off-by: Shiyang Ruan <ruansy.fnst@fujitsu.com> --- fs/dax.c | 37 +++++++++++++++++++++++++++++++++++++ 1 file changed, 37 insertions(+)