Sparse static analysis tools generate a warning with this message
"Using plain integer as NULL pointer". In this case this warning is
being shown because we are trying to initialize  pointer to NULL using
integer value 0.

Signed-off-by: Abhinav Singh <singhabhinav9051571833@gmail.com>
Link: https://lore.kernel.org/r/20231108044550.1006555-1-singhabhinav9051571833@gmail.com


Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Christian Brauner <brauner@kernel.org>

The one caller of DAX lock/unlock page already calls compound_head(), so
use page_folio() instead, then use a folio throughout the DAX code to
remove uses of page->mapping and page->index.

[jane.chu@oracle.com: add comment to mf_generic_kill_procss(), simplify mf_generic_kill_procs:folio initialization]
  Link: https://lkml.kernel.org/r/20230908222336.186313-1-jane.chu@oracle.com
Link: https://lkml.kernel.org/r/20230822231314.349200-1-willy@infradead.org


Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Jane Chu <jane.chu@oracle.com>
Acked-by: Naoya Horiguchi <naoya.horiguchi@nec.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Jane Chu <jane.chu@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Remove the unnecessary encoding of page order into an enum and pass the
page order directly.  That lets us get rid of pe_order().

The switch constructs have to be changed to if/else constructs to prevent
GCC from warning on builds with 3-level page tables where PMD_ORDER and
PUD_ORDER have the same value.

If you are looking at this commit because your driver stopped compiling,
look at the previous commit as well and audit your driver to be sure it
doesn't depend on mmap_lock being held in its ->huge_fault method.

[willy@infradead.org: use "order %u" to match the (non dev_t) style]
  Link: https://lkml.kernel.org/r/ZOUYekbtTv+n8hYf@casper.infradead.org
Link: https://lkml.kernel.org/r/20230818202335.2739663-4-willy@infradead.org


Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Patch series "Change calling convention for ->huge_fault", v2.

There are two unrelated changes to the calling convention for
->huge_fault.  I've bundled them together to help people notice the
change.  The first is to improve scalability of DAX page faults by
allowing them to be handled under the VMA lock.  The second is to remove
enum page_entry_size since it's really unnecessary.  The changelogs and
documentation updates hopefully work to that end.


This patch (of 3):

Allow this to be used in generic code.  Also add PUD_ORDER.

Link: https://lkml.kernel.org/r/20230818202335.2739663-1-willy@infradead.org
Link: https://lkml.kernel.org/r/20230818202335.2739663-2-willy@infradead.org


Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

When multiple processes mmap() a dax file, then at some point,
a process issues a 'load' and consumes a hwpoison, the process
receives a SIGBUS with si_code = BUS_MCEERR_AR and with si_lsb
set for the poison scope. Soon after, any other process issues
a 'load' to the poisoned page (that is unmapped from the kernel
side by memory_failure), it receives a SIGBUS with
si_code = BUS_ADRERR and without valid si_lsb.

This is confusing to user, and is different from page fault due
to poison in RAM memory, also some helpful information is lost.

Channel dax backend driver's poison detection to the filesystem
such that instead of reporting VM_FAULT_SIGBUS, it could report
VM_FAULT_HWPOISON.

If user level block IO syscalls fail due to poison, the errno will
be converted to EIO to maintain block API consistency.

Signed-off-by: Jane Chu <jane.chu@oracle.com>
Link: https://lore.kernel.org/r/20230615181325.1327259-2-jane.chu@oracle.com


Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Vishal Verma <vishal.l.verma@intel.com>

The variable 'error' is being assigned a value that is never read,
the assignment and the variable and redundant and can be removed.
Cleans up clang scan build warning:

fs/dax.c:1880:10: warning: Although the value stored to 'error' is
used in the enclosing expression, the value is never actually read
from 'error' [deadcode.DeadStores]

Signed-off-by: Colin Ian King <colin.i.king@gmail.com>
Link: https://lore.kernel.org/r/20230621130256.2676126-1-colin.i.king@gmail.com


Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Vishal Verma <vishal.l.verma@intel.com>

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. 

This results in a WARNing:

[   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 ]---


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/

Link: https://lkml.kernel.org/r/1679653680-2-1-git-send-email-ruansy.fnst@fujitsu.com


Fixes: f80e1668 ("fsdax: invalidate pages when CoW")
Signed-off-by: Shiyang Ruan <ruansy.fnst@fujitsu.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Darrick J. Wong <djwong@kernel.org>
Cc: Jan Kara <jack@suse.cz>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

In an dedupe comparison iter loop, the length of iomap_iter decreases
because it implies the remaining length after each iteration.

The dedupe command will fail with -EIO if the range is larger than one 
page size and not aligned to the page size.  Also report warning in dmesg:

[ 4338.498374] ------------[ cut here ]------------
[ 4338.498689] WARNING: CPU: 3 PID: 1415645 at fs/iomap/iter.c:16 
...

The compare function should use the min length of the current iters,
not the total length.

Link: https://lkml.kernel.org/r/1679469958-2-1-git-send-email-ruansy.fnst@fujitsu.com


Fixes: 0e79e373 ("fsdax: dedupe: iter two files at the same time")
Signed-off-by: Shiyang Ruan <ruansy.fnst@fujitsu.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

unshare copies data from source to destination.  But if the source is
HOLE or UNWRITTEN extents, we should zero the destination, otherwise
the HOLE or UNWRITTEN part will be user-visible old data of the new
allocated extent.

Found by running generic/649 while mounting with -o dax=always on pmem.

Link: https://lkml.kernel.org/r/1679483469-2-1-git-send-email-ruansy.fnst@fujitsu.com


Fixes: d984648e ("fsdax,xfs: port unshare to fsdax")
Signed-off-by: Shiyang Ruan <ruansy.fnst@fujitsu.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Darrick J. Wong <djwong@kernel.org>
Cc: Jan Kara <jack@suse.cz>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

The copy_mc_to_kernel() will return 0 if it executed successfully.  Then
the return value should be set to the length it copied.

[akpm@linux-foundation.org: don't mess up `ret', per Matthew]
Link: https://lkml.kernel.org/r/1675341227-14-1-git-send-email-ruansy.fnst@fujitsu.com


Fixes: d984648e ("fsdax,xfs: port unshare to fsdax")
Signed-off-by: Shiyang Ruan <ruansy.fnst@fujitsu.com>
Cc: Darrick J. Wong <djwong@kernel.org>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Matthew Wilcox <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Implement unshare in fsdax mode: copy data from srcmap to iomap.

Link: https://lkml.kernel.org/r/1669908753-169-1-git-send-email-ruansy.fnst@fujitsu.com


Signed-off-by: Shiyang Ruan <ruansy.fnst@fujitsu.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

The iomap_iter() on a range of one file may loop more than once.  In this
case, the inner dst_iter can update its iomap but the outer src_iter
can't.  This may cause the wrong remapping in filesystem.  Let them called
at the same time.

Link: https://lkml.kernel.org/r/1669908701-93-1-git-send-email-ruansy.fnst@fujitsu.com


Signed-off-by: Shiyang Ruan <ruansy.fnst@fujitsu.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

If a dax page is shared, mapread at different offsets can also trigger
page fault on same dax page.  So, change the flag from "cow" to "shared". 
And get the shared flag from filesystem when read.

Link: https://lkml.kernel.org/r/1669908538-55-5-git-send-email-ruansy.fnst@fujitsu.com


Signed-off-by: Shiyang Ruan <ruansy.fnst@fujitsu.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

If srcmap contains invalid data, such as HOLE and UNWRITTEN, the dest page
should be zeroed.  Otherwise, since it's a pmem, old data may remains on
the dest page, the result of CoW will be incorrect.

The function name is also not easy to understand, rename it to
"dax_iomap_copy_around()", which means it copies data around the range.

[akpm@linux-foundation.org: update dax_iomap_copy_around() kerneldoc, per Darrick]
Link: https://lkml.kernel.org/r/1669973145-318-1-git-send-email-ruansy.fnst@fujitsu.com
Link: https://lkml.kernel.org/r/1669908538-55-4-git-send-email-ruansy.fnst@fujitsu.com


Signed-off-by: Shiyang Ruan <ruansy.fnst@fujitsu.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

CoW changes the share state of a dax page, but the share count of the page
isn't updated.  The next time access this page, it should have been a
newly accessed, but old association exists.  So, we need to clear the
share state when CoW happens, in both dax_iomap_rw() and dax_zero_iter().

Link: https://lkml.kernel.org/r/1669908538-55-3-git-send-email-ruansy.fnst@fujitsu.com


Signed-off-by: Shiyang Ruan <ruansy.fnst@fujitsu.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Patch series "fsdax,xfs: fix warning messages", v2.

Many testcases failed in dax+reflink mode with warning message in dmesg.
Such as generic/051,075,127.  The warning message is like this:
[  775.509337] ------------[ cut here ]------------
[  775.509636] WARNING: CPU: 1 PID: 16815 at fs/dax.c:386 dax_insert_entry.cold+0x2e/0x69
[  775.510151] Modules linked in: auth_rpcgss oid_registry nfsv4 algif_hash af_alg af_packet nft_reject_inet nf_reject_ipv4 nf_reject_ipv6 nft_reject nft_ct nft_chain_nat iptable_nat nf_nat nf_conntrack nf_defrag_ipv6 nf_defrag_ipv4 ip_set nf_tables nfnetlink ip6table_filter ip6_tables iptable_filter ip_tables x_tables dax_pmem nd_pmem nd_btt sch_fq_codel configfs xfs libcrc32c fuse
[  775.524288] CPU: 1 PID: 16815 Comm: fsx Kdump: loaded Tainted: G        W          6.1.0-rc4+ #164 eb34e4ee4200c7cbbb47de2b1892c5a3e027fd6d
[  775.524904] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS Arch Linux 1.16.0-3-3 04/01/2014
[  775.525460] RIP: 0010:dax_insert_entry.cold+0x2e/0x69
[  775.525797] Code: c7 c7 18 eb e0 81 48 89 4c 24 20 48 89 54 24 10 e8 73 6d ff ff 48 83 7d 18 00 48 8b 54 24 10 48 8b 4c 24 20 0f 84 e3 e9 b9 ff <0f> 0b e9 dc e9 b9 ff 48 c7 c6 a0 20 c3 81 48 c7 c7 f0 ea e0 81 48
[  775.526708] RSP: 0000:ffffc90001d57b30 EFLAGS: 00010082
[  775.527042] RAX: 000000000000002a RBX: 0000000000000000 RCX: 0000000000000042
[  775.527396] RDX: ffffea000a0f6c80 RSI: ffffffff81dfab1b RDI: 00000000ffffffff
[  775.527819] RBP: ffffea000a0f6c40 R08: 0000000000000000 R09: ffffffff820625e0
[  775.528241] R10: ffffc90001d579d8 R11: ffffffff820d2628 R12: ffff88815fc98320
[  775.528598] R13: ffffc90001d57c18 R14: 0000000000000000 R15: 0000000000000001
[  775.528997] FS:  00007f39fc75d740(0000) GS:ffff88817bc80000(0000) knlGS:0000000000000000
[  775.529474] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  775.529800] CR2: 00007f39fc772040 CR3: 0000000107eb6001 CR4: 00000000003706e0
[  775.530214] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[  775.530592] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[  775.531002] Call Trace:
[  775.531230]  <TASK>
[  775.531444]  dax_fault_iter+0x267/0x6c0
[  775.531719]  dax_iomap_pte_fault+0x198/0x3d0
[  775.532002]  __xfs_filemap_fault+0x24a/0x2d0 [xfs aa8d25411432b306d9554da38096f4ebb86bdfe7]
[  775.532603]  __do_fault+0x30/0x1e0
[  775.532903]  do_fault+0x314/0x6c0
[  775.533166]  __handle_mm_fault+0x646/0x1250
[  775.533480]  handle_mm_fault+0xc1/0x230
[  775.533810]  do_user_addr_fault+0x1ac/0x610
[  775.534110]  exc_page_fault+0x63/0x140
[  775.534389]  asm_exc_page_fault+0x22/0x30
[  775.534678] RIP: 0033:0x7f39fc55820a
[  775.534950] Code: 00 01 00 00 00 74 99 83 f9 c0 0f 87 7b fe ff ff c5 fe 6f 4e 20 48 29 fe 48 83 c7 3f 49 8d 0c 10 48 83 e7 c0 48 01 fe 48 29 f9 <f3> a4 c4 c1 7e 7f 00 c4 c1 7e 7f 48 20 c5 f8 77 c3 0f 1f 44 00 00
[  775.535839] RSP: 002b:00007ffc66a08118 EFLAGS: 00010202
[  775.536157] RAX: 00007f39fc772001 RBX: 0000000000042001 RCX: 00000000000063c1
[  775.536537] RDX: 0000000000006400 RSI: 00007f39fac42050 RDI: 00007f39fc772040
[  775.536919] RBP: 0000000000006400 R08: 00007f39fc772001 R09: 0000000000042000
[  775.537304] R10: 0000000000000001 R11: 0000000000000246 R12: 0000000000000001
[  775.537694] R13: 00007f39fc772000 R14: 0000000000006401 R15: 0000000000000003
[  775.538086]  </TASK>
[  775.538333] ---[ end trace 0000000000000000 ]---

This also affects dax+noreflink mode if we run the test after a
dax+reflink test.  So, the most urgent thing is solving the warning
messages.

With these fixes, most warning messages in dax_associate_entry() are gone.
But honestly, generic/388 will randomly failed with the warning.  The
case shutdown the xfs when fsstress is running, and do it for many times. 
I think the reason is that dax pages in use are not able to be invalidated
in time when fs is shutdown.  The next time dax page to be associated, it
still remains the mapping value set last time.  I'll keep on solving it.

The warning message in dax_writeback_one() can also be fixed because of
the dax unshare.


This patch (of 8):

fsdax page is used not only when CoW, but also mapread.  To make the it
easily understood, use 'share' to indicate that the dax page is shared by
more than one extent.  And add helper functions to use it.

Also, the flag needs to be renamed to PAGE_MAPPING_DAX_SHARED.

[ruansy.fnst@fujitsu.com: rename several functions]
  Link: https://lkml.kernel.org/r/1669972991-246-1-git-send-email-ruansy.fnst@fujitsu.com
[ruansy.fnst@fujitsu.com: v2.2]
  Link: https://lkml.kernel.org/r/1670381359-53-1-git-send-email-ruansy.fnst@fujitsu.com
Link: https://lkml.kernel.org/r/1669908538-55-1-git-send-email-ruansy.fnst@fujitsu.com
Link: https://lkml.kernel.org/r/1669908538-55-2-git-send-email-ruansy.fnst@fujitsu.com


Signed-off-by: Shiyang Ruan <ruansy.fnst@fujitsu.com>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

I got an infinite loop and a WARNING report when executing a tail command
in virtiofs.

  WARNING: CPU: 10 PID: 964 at fs/iomap/iter.c:34 iomap_iter+0x3a2/0x3d0
  Modules linked in:
  CPU: 10 PID: 964 Comm: tail Not tainted 5.19.0-rc7
  Call Trace:
  <TASK>
  dax_iomap_rw+0xea/0x620
  ? __this_cpu_preempt_check+0x13/0x20
  fuse_dax_read_iter+0x47/0x80
  fuse_file_read_iter+0xae/0xd0
  new_sync_read+0xfe/0x180
  ? 0xffffffff81000000
  vfs_read+0x14d/0x1a0
  ksys_read+0x6d/0xf0
  __x64_sys_read+0x1a/0x20
  do_syscall_64+0x3b/0x90
  entry_SYSCALL_64_after_hwframe+0x63/0xcd

The tail command will call read() with a count of 0. In this case,
iomap_iter() will report this WARNING, and always return 1 which casuing
the infinite loop in dax_iomap_rw().

Fixing by checking count whether is 0 in dax_iomap_rw().

Fixes: ca289e0b ("fsdax: switch dax_iomap_rw to use iomap_iter")
Signed-off-by: Li Jinlin <lijinlin3@huawei.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Link: https://lore.kernel.org/r/20220725032050.3873372-1-lijinlin3@huawei.com


Signed-off-by: Dan Williams <dan.j.williams@intel.com>

With dax we cannot deal with readpage() etc.  So, we create a dax
comparison function which is similar with vfs_dedupe_file_range_compare().
And introduce dax_remap_file_range_prep() for filesystem use.

Link: https://lkml.kernel.org/r/20220603053738.1218681-13-ruansy.fnst@fujitsu.com


Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.com>
Signed-off-by: Shiyang Ruan <ruansy.fnst@fujitsu.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Dan Williams <dan.j.wiliams@intel.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Goldwyn Rodrigues <rgoldwyn@suse.de>
Cc: Jane Chu <jane.chu@oracle.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Naoya Horiguchi <naoya.horiguchi@nec.com>
Cc: Ritesh Harjani <riteshh@linux.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Punch hole on a reflinked file needs dax_iomap_cow_copy() too.  Otherwise,
data in not aligned area will be not correct.  So, add the CoW operation
for not aligned case in dax_memzero().

Link: https://lkml.kernel.org/r/20220603053738.1218681-12-ruansy.fnst@fujitsu.com


Signed-off-by: Shiyang Ruan <ruansy.fnst@fujitsu.com>
Reviewed-by: Ritesh Harjani <riteshh@linux.ibm.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Dan Williams <dan.j.wiliams@intel.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Goldwyn Rodrigues <rgoldwyn@suse.com>
Cc: Goldwyn Rodrigues <rgoldwyn@suse.de>
Cc: Jane Chu <jane.chu@oracle.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Naoya Horiguchi <naoya.horiguchi@nec.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Replace the existing entry to the newly allocated one in case of CoW. 
Also, we mark the entry as PAGECACHE_TAG_TOWRITE so writeback marks this
entry as writeprotected.  This helps us snapshots so new write pagefaults
after snapshots trigger a CoW.

Link: https://lkml.kernel.org/r/20220603053738.1218681-11-ruansy.fnst@fujitsu.com


Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.com>
Signed-off-by: Shiyang Ruan <ruansy.fnst@fujitsu.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Ritesh Harjani <riteshh@linux.ibm.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Dan Williams <dan.j.wiliams@intel.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Goldwyn Rodrigues <rgoldwyn@suse.de>
Cc: Jane Chu <jane.chu@oracle.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Naoya Horiguchi <naoya.horiguchi@nec.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

In the case where the iomap is a write operation and iomap is not equal to
srcmap after iomap_begin, we consider it is a CoW operation.

In this case, the destination (iomap->addr) points to a newly allocated
extent.  It is needed to copy the data from srcmap to the extent.  In
theory, it is better to copy the head and tail ranges which is outside of
the non-aligned area instead of copying the whole aligned range.  But in
dax page fault, it will always be an aligned range.  So copy the whole
range in this case.

Link: https://lkml.kernel.org/r/20220603053738.1218681-10-ruansy.fnst@fujitsu.com


Signed-off-by: Shiyang Ruan <ruansy.fnst@fujitsu.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Dan Williams <dan.j.wiliams@intel.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Goldwyn Rodrigues <rgoldwyn@suse.com>
Cc: Goldwyn Rodrigues <rgoldwyn@suse.de>
Cc: Jane Chu <jane.chu@oracle.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Naoya Horiguchi <naoya.horiguchi@nec.com>
Cc: Ritesh Harjani <riteshh@linux.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Add address output in dax_iomap_pfn() in order to perform a memcpy() in
CoW case.  Since this function both output address and pfn, rename it to
dax_iomap_direct_access().

[ruansy.fnst@fujitsu.com: initialize `rc', per Dan]
  Link: https://lore.kernel.org/linux-fsdevel/Yp8FUZnO64Qvyx5G@kili/
  Link: https://lkml.kernel.org/r/20220607143837.161174-1-ruansy.fnst@fujitsu.com
Link: https://lkml.kernel.org/r/20220603053738.1218681-9-ruansy.fnst@fujitsu.com


Signed-off-by: Shiyang Ruan <ruansy.fnst@fujitsu.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Ritesh Harjani <riteshh@linux.ibm.com>
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Dan Williams <dan.j.wiliams@intel.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Goldwyn Rodrigues <rgoldwyn@suse.com>
Cc: Goldwyn Rodrigues <rgoldwyn@suse.de>
Cc: Jane Chu <jane.chu@oracle.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Naoya Horiguchi <naoya.horiguchi@nec.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Introduce a PAGE_MAPPING_DAX_COW flag to support association with CoW file
mappings.  In this case, since the dax-rmap has already took the
responsibility to look up for shared files by given dax page, the
page->mapping is no longer to used for rmap but for marking that this dax
page is shared.  And to make sure disassociation works fine, we use
page->index as refcount, and clear page->mapping to the initial state when
page->index is decreased to 0.

With the help of this new flag, it is able to distinguish normal case and
CoW case, and keep the warning in normal case.

Link: https://lkml.kernel.org/r/20220603053738.1218681-8-ruansy.fnst@fujitsu.com


Signed-off-by: Shiyang Ruan <ruansy.fnst@fujitsu.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Dan Williams <dan.j.wiliams@intel.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Goldwyn Rodrigues <rgoldwyn@suse.com>
Cc: Goldwyn Rodrigues <rgoldwyn@suse.de>
Cc: Jane Chu <jane.chu@oracle.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Naoya Horiguchi <naoya.horiguchi@nec.com>
Cc: Ritesh Harjani <riteshh@linux.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

The current dax_lock_page() locks dax entry by obtaining mapping and index
in page.  To support 1-to-N RMAP in NVDIMM, we need a new function to lock
a specific dax entry corresponding to this file's mapping,index.  And
output the page corresponding to the specific dax entry for caller use.

Link: https://lkml.kernel.org/r/20220603053738.1218681-5-ruansy.fnst@fujitsu.com


Signed-off-by: Shiyang Ruan <ruansy.fnst@fujitsu.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Dan Williams <dan.j.wiliams@intel.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Goldwyn Rodrigues <rgoldwyn@suse.com>
Cc: Goldwyn Rodrigues <rgoldwyn@suse.de>
Cc: Jane Chu <jane.chu@oracle.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Naoya Horiguchi <naoya.horiguchi@nec.com>
Cc: Ritesh Harjani <riteshh@linux.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

It is unnecessary to check and set did_zero value in while() loop
in dax_zero_iter(), we can set did_zero to true only when zeroing
successfully at last.

Signed-off-by: Kaixu Xia <kaixuxia@tencent.com>
Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>

Introduce dax_recovery_write() operation. The function is used to
recover a dax range that contains poison. Typical use case is when
a user process receives a SIGBUS with si_code BUS_MCEERR_AR
indicating poison(s) in a dax range, in response, the user process
issues a pwrite() to the page-aligned dax range, thus clears the
poison and puts valid data in the range.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jane Chu <jane.chu@oracle.com>
Link: https://lore.kernel.org/r/20220422224508.440670-6-jane.chu@oracle.com


Signed-off-by: Dan Williams <dan.j.williams@intel.com>

Up till now, dax_direct_access() is used implicitly for normal
access, but for the purpose of recovery write, dax range with
poison is requested.  To make the interface clear, introduce
	enum dax_access_mode {
		DAX_ACCESS,
		DAX_RECOVERY_WRITE,
	}
where DAX_ACCESS is used for normal dax access, and
DAX_RECOVERY_WRITE is used for dax recovery write.

Suggested-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Jane Chu <jane.chu@oracle.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Cc: Mike Snitzer <snitzer@redhat.com>
Reviewed-by: Vivek Goyal <vgoyal@redhat.com>
Link: https://lore.kernel.org/r/165247982851.52965.11024212198889762949.stgit@dwillia2-desk3.amr.corp.intel.com


Signed-off-by: Dan Williams <dan.j.williams@intel.com>

Currently dax_mapping_entry_mkclean() fails to clean and write protect the
pte entry within a DAX PMD entry during an *sync operation.  This can
result in data loss in the following sequence:

  1) process A mmap write to DAX PMD, dirtying PMD radix tree entry and
     making the pmd entry dirty and writeable.
  2) process B mmap with the @offset (e.g. 4K) and @length (e.g. 4K)
     write to the same file, dirtying PMD radix tree entry (already
     done in 1)) and making the pte entry dirty and writeable.
  3) fsync, flushing out PMD data and cleaning the radix tree entry. We
     currently fail to mark the pte entry as clean and write protected
     since the vma of process B is not covered in dax_entry_mkclean().
  4) process B writes to the pte. These don't cause any page faults since
     the pte entry is dirty and writeable. The radix tree entry remains
     clean.
  5) fsync, which fails to flush the dirty PMD data because the radix tree
     entry was clean.
  6) crash - dirty data that should have been fsync'd as part of 5) could
     still have been in the processor cache, and is lost.

Just to use pfn_mkclean_range() to clean the pfns to fix this issue.

Link: https://lkml.kernel.org/r/20220403053957.10770-6-songmuchun@bytedance.com


Fixes: 4b4bb46d ("dax: clear dirty entry tags on cache flush")
Signed-off-by: Muchun Song <songmuchun@bytedance.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jan Kara <jack@suse.cz>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Ralph Campbell <rcampbell@nvidia.com>
Cc: Ross Zwisler <zwisler@kernel.org>
Cc: Xiongchun Duan <duanxiongchun@bytedance.com>
Cc: Xiyu Yang <xiyuyang19@fudan.edu.cn>
Cc: Yang Shi <shy828301@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

The flush_cache_page() only remove a PAGE_SIZE sized range from the cache.
However, it does not cover the full pages in a THP except a head page. 
Replace it with flush_cache_range() to fix this issue.  This is just a
documentation issue with the respect to properly documenting the expected
usage of cache flushing before modifying the pmd.  However, in practice
this is not a problem due to the fact that DAX is not available on
architectures with virtually indexed caches per:

  commit d92576f1 ("dax: does not work correctly with virtual aliasing caches")

Link: https://lkml.kernel.org/r/20220403053957.10770-3-songmuchun@bytedance.com


Fixes: f729c8c9 ("dax: wrprotect pmd_t in dax_mapping_entry_mkclean")
Signed-off-by: Muchun Song <songmuchun@bytedance.com>
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jan Kara <jack@suse.cz>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Ralph Campbell <rcampbell@nvidia.com>
Cc: Ross Zwisler <zwisler@kernel.org>
Cc: Xiongchun Duan <duanxiongchun@bytedance.com>
Cc: Xiyu Yang <xiyuyang19@fudan.edu.cn>
Cc: Yang Shi <shy828301@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

The function name has been changed, so the description should be updated
too.

Signed-off-by: Shiyang Ruan <ruansy.fnst@fujitsu.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20220127124058.1172422-5-ruansy.fnst@fujitsu.com


Signed-off-by: Dan Williams <dan.j.williams@intel.com>

There is no good reason to keep genhd.h separate from the main blkdev.h
header that includes it.  So fold the contents of genhd.h into blkdev.h
and remove genhd.h entirely.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Link: https://lore.kernel.org/r/20220124093913.742411-4-hch@lst.de


Signed-off-by: Jens Axboe <axboe@kernel.dk>

These methods indirect the actual DAX read/write path.  In the end pmem
uses magic flush and mc safe variants and fuse and dcssblk use plain ones
while device mapper picks redirects to the underlying device.

Add set_dax_nocache() and set_dax_nomc() APIs to control which copy
routines are used to remove indirect call from the read/write fast path
as well as a lot of boilerplate code.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Vivek Goyal <vgoyal@redhat.com> [virtiofs]
Link: https://lore.kernel.org/r/20211215084508.435401-5-hch@lst.de


Signed-off-by: Dan Williams <dan.j.williams@intel.com>

Remove the last user of ->bdev in dax.c by requiring the file system to
pass in an address that already includes the DAX offset.  As part of the
only set ->bdev or ->daxdev when actually required in the ->iomap_begin
methods.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Gao Xiang <hsiangkao@linux.alibaba.com> [erofs]
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Link: https://lore.kernel.org/r/20211129102203.2243509-27-hch@lst.de


Signed-off-by: Dan Williams <dan.j.williams@intel.com>

Add a flag so that the file system can easily detect DAX operations
based just on the iomap operation requested instead of looking at
inode state using IS_DAX.  This will be needed to apply the to be
added partition offset only for operations that actually use DAX,
but not things like fiemap that are based on the block device.
In the long run it should also allow turning the bdev, dax_dev
and inline_data into a union.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Link: https://lore.kernel.org/r/20211129102203.2243509-25-hch@lst.de


Signed-off-by: Dan Williams <dan.j.williams@intel.com>

Unshare the DAX and iomap buffered I/O page zeroing code.  This code
previously did a IS_DAX check deep inside the iomap code, which in
fact was the only DAX check in the code.  Instead move these checks
into the callers.  Most callers already have DAX special casing anyway
and XFS will need it for reflink support as well.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Link: https://lore.kernel.org/r/20211129102203.2243509-19-hch@lst.de


Signed-off-by: Dan Williams <dan.j.williams@intel.com>

Factor out a helper for the "manual" zeroing of a DAX range to clean
up dax_iomap_zero a lot.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Link: https://lore.kernel.org/r/20211129102203.2243509-18-hch@lst.de


Signed-off-by: Dan Williams <dan.j.williams@intel.com>

The file relative offset must have the same alignment as the storage
offset, so use that and get rid of the call to iomap_sector.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Link: https://lore.kernel.org/r/20211129102203.2243509-17-hch@lst.de


Signed-off-by: Dan Williams <dan.j.williams@intel.com>

Replace the two steps of dax_iomap_sector and bdev_dax_pgoff with a
single dax_iomap_pgoff helper that avoids lots of cumbersome sector
conversions.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Link: https://lore.kernel.org/r/20211129102203.2243509-15-hch@lst.de


Signed-off-by: Dan Williams <dan.j.williams@intel.com>

Just pass the vm_fault and iomap_iter structures, and figure out the rest
locally.  Note that this requires moving dax_iomap_sector up in the file.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Link: https://lore.kernel.org/r/20211129102203.2243509-14-hch@lst.de


Signed-off-by: Dan Williams <dan.j.williams@intel.com>

Despite its name copy_user_page expected kernel addresses, which is what
we already have.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Link: https://lore.kernel.org/r/20211129102203.2243509-13-hch@lst.de


Signed-off-by: Dan Williams <dan.j.williams@intel.com>