linux-toradex.git/drivers/ata/libata-core.c, branch v3.19.2 Linux kernel for Apalis and Colibri modules libata: allow sata_sil24 to opt-out of tag ordered submission 2015-01-19T14:10:07+00:00 Dan Williams dan.j.williams@intel.com 2015-01-16T23:13:02+00:00 72dd299d5039a336493993dcc63413cf31d0e662 Ronny reports: https://bugzilla.kernel.org/show_bug.cgi?id=87101 "Since commit 8a4aeec8d "libata/ahci: accommodate tag ordered controllers" the access to the harddisk on the first SATA-port is failing on its first access. The access to the harddisk on the second port is working normal. When reverting the above commit, access to both harddisks is working fine again." Maintain tag ordered submission as the default, but allow sata_sil24 to continue with the old behavior. Cc: <stable@vger.kernel.org> Cc: Tejun Heo <tj@kernel.org> Reported-by: Ronny Hegewald <Ronny.Hegewald@online.de> Signed-off-by: Dan Williams <dan.j.williams@intel.com> Signed-off-by: Tejun Heo <tj@kernel.org> 
Ronny reports: https://bugzilla.kernel.org/show_bug.cgi?id=87101
    "Since commit 8a4aeec8d "libata/ahci: accommodate tag ordered
    controllers" the access to the harddisk on the first SATA-port is
    failing on its first access. The access to the harddisk on the
    second port is working normal.

    When reverting the above commit, access to both harddisks is working
    fine again."

Maintain tag ordered submission as the default, but allow sata_sil24 to
continue with the old behavior.

Cc: <stable@vger.kernel.org>
Cc: Tejun Heo <tj@kernel.org>
Reported-by: Ronny Hegewald <Ronny.Hegewald@online.de>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
libata: Whitelist SSDs that are known to properly return zeroes after TRIM 2015-01-08T15:35:40+00:00 Martin K. Petersen martin.petersen@oracle.com 2015-01-08T15:34:27+00:00 e61f7d1c3c07a7e51036b0796749edb00deff845 As defined, the DRAT (Deterministic Read After Trim) and RZAT (Return Zero After Trim) flags in the ATA Command Set are unreliable in the sense that they only define what happens if the device successfully executed the DSM TRIM command. TRIM is only advisory, however, and the device is free to silently ignore all or parts of the request. In practice this renders the DRAT and RZAT flags completely useless and because the results are unpredictable we decided to disable discard in MD for 3.18 to avoid the risk of data corruption. Hardware vendors in the real world obviously need better guarantees than what the standards bodies provide. Unfortuntely those guarantees are encoded in product requirements documents rather than somewhere we can key off of them programatically. So we are compelled to disabling discard_zeroes_data for all devices unless we explicitly have data to support whitelisting them. This patch whitelists SSDs from a few of the main vendors. None of the whitelists are based on written guarantees. They are purely based on empirical evidence collected from internal and external users that have tested or qualified these drives in RAID deployments. The whitelist is only meant as a starting point and is by no means comprehensive: - All intel SSD models except for 510 - Micron M5?0/M600 - Samsung SSDs - Seagate SSDs Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Tejun Heo <tj@kernel.org> 
As defined, the DRAT (Deterministic Read After Trim) and RZAT (Return
Zero After Trim) flags in the ATA Command Set are unreliable in the
sense that they only define what happens if the device successfully
executed the DSM TRIM command. TRIM is only advisory, however, and the
device is free to silently ignore all or parts of the request.

In practice this renders the DRAT and RZAT flags completely useless and
because the results are unpredictable we decided to disable discard in
MD for 3.18 to avoid the risk of data corruption.

Hardware vendors in the real world obviously need better guarantees than
what the standards bodies provide. Unfortuntely those guarantees are
encoded in product requirements documents rather than somewhere we can
key off of them programatically. So we are compelled to disabling
discard_zeroes_data for all devices unless we explicitly have data to
support whitelisting them.

This patch whitelists SSDs from a few of the main vendors. None of the
whitelists are based on written guarantees. They are purely based on
empirical evidence collected from internal and external users that have
tested or qualified these drives in RAID deployments.

The whitelist is only meant as a starting point and is by no means
comprehensive:

   - All intel SSD models except for 510
   - Micron M5?0/M600
   - Samsung SSDs
   - Seagate SSDs

Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Tejun Heo <tj@kernel.org>
libata: Implement ATA_DEV_ZAC 2014-11-05T16:22:06+00:00 Hannes Reinecke hare@suse.de 2014-11-05T12:08:21+00:00 9162c6579bf90b3f5ddb7e3a6c6fa946c1b4cbeb Add new ATA device type for ZAC devices. Acked-by: Christoph Hellwig <hch@lst.de> Acked-by: Tejun Heo <tj@kernel.org> Signed-off-by: Hannes Reinecke <hare@suse.de> Signed-off-by: Tejun Heo <tj@kernel.org> 
Add new ATA device type for ZAC devices.

Acked-by: Christoph Hellwig <hch@lst.de>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Tejun Heo <tj@kernel.org>
Merge branch 'for-3.18' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/libata 2014-10-10T11:23:11+00:00 Linus Torvalds torvalds@linux-foundation.org 2014-10-10T11:23:11+00:00 d9428f09763d307a6d2220c4bbb01d8fc5c55b52 Pull libata update from Tejun Heo: "AHCI is getting per-port irq handling and locks for better scalability. The gain is not huge but measureable with multiple high iops devices connected to the same host; however, the value of threaded IRQ handling seems negligible for AHCI and it likely will revert to non-threaded handling soon. Another noteworthy change is George Spelvin's "libata: Un-break ATA blacklist". During 3.17 devel cycle, the libata blacklist glob matching got generalized and rewritten; unfortunately, the patch forgot to swap arguments to match the new match function and ended up breaking blacklist matching completely. It got noticed only a couple days ago so it couldn't make for-3.17-fixes either. :( Other than the above two, nothing too interesting - the usual cleanup churns and device-specific changes" * 'for-3.18' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/libata: (22 commits) pata_serverworks: disable 64-KB DMA transfers on Broadcom OSB4 IDE Controller libata: Un-break ATA blacklist AHCI: Do not acquire ata_host::lock from single IRQ handler AHCI: Optimize single IRQ interrupt processing AHCI: Do not read HOST_IRQ_STAT reg in multi-MSI mode AHCI: Make few function names more descriptive AHCI: Move host activation code into ahci_host_activate() AHCI: Move ahci_host_activate() function to libahci.c AHCI: Pass SCSI host template as arg to ahci_host_activate() ata: pata_imx: Use the SIMPLE_DEV_PM_OPS() macro AHCI: Cleanup checking of multiple MSIs/SLM modes libata-sff: Fix controllers with no ctl port ahci_xgene: Fix the error print invalid resource for APM X-Gene SoC AHCI SATA Host Controller driver. libata: change ata_<foo>_printk routines to return void ata: qcom: Add device tree bindings information ahci-platform: Bump max number of clocks to 5 ahci: ahci_p5wdh_workaround - constify DMI table libahci_platform: Staticize ahci_platform_<en/dis>able_phys() pata_platform: Remove useless irq_flags field pata_of_platform: Remove "electra-ide" quirk ... 
Pull libata update from Tejun Heo:
 "AHCI is getting per-port irq handling and locks for better
  scalability.  The gain is not huge but measureable with multiple high
  iops devices connected to the same host; however, the value of
  threaded IRQ handling seems negligible for AHCI and it likely will
  revert to non-threaded handling soon.

  Another noteworthy change is George Spelvin's "libata: Un-break ATA
  blacklist".  During 3.17 devel cycle, the libata blacklist glob
  matching got generalized and rewritten; unfortunately, the patch
  forgot to swap arguments to match the new match function and ended up
  breaking blacklist matching completely.  It got noticed only a couple
  days ago so it couldn't make for-3.17-fixes either.  :(

  Other than the above two, nothing too interesting - the usual cleanup
  churns and device-specific changes"

* 'for-3.18' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/libata: (22 commits)
  pata_serverworks: disable 64-KB DMA transfers on Broadcom OSB4 IDE Controller
  libata: Un-break ATA blacklist
  AHCI: Do not acquire ata_host::lock from single IRQ handler
  AHCI: Optimize single IRQ interrupt processing
  AHCI: Do not read HOST_IRQ_STAT reg in multi-MSI mode
  AHCI: Make few function names more descriptive
  AHCI: Move host activation code into ahci_host_activate()
  AHCI: Move ahci_host_activate() function to libahci.c
  AHCI: Pass SCSI host template as arg to ahci_host_activate()
  ata: pata_imx: Use the SIMPLE_DEV_PM_OPS() macro
  AHCI: Cleanup checking of multiple MSIs/SLM modes
  libata-sff: Fix controllers with no ctl port
  ahci_xgene: Fix the error print invalid resource for APM X-Gene SoC AHCI SATA Host Controller driver.
  libata: change ata_<foo>_printk routines to return void
  ata: qcom: Add device tree bindings information
  ahci-platform: Bump max number of clocks to 5
  ahci: ahci_p5wdh_workaround - constify DMI table
  libahci_platform: Staticize ahci_platform_<en/dis>able_phys()
  pata_platform: Remove useless irq_flags field
  pata_of_platform: Remove "electra-ide" quirk
  ...
libata: Un-break ATA blacklist 2014-10-07T21:10:00+00:00 George Spelvin linux@horizon.com 2014-10-07T11:26:38+00:00 1c40279960bcd7d52dbdf1d466b20d24b99176c8 lib/glob.c provides a new glob_match() function, with arguments in (pattern, string) order. It replaced a private function with arguments in (string, pattern) order, but I didn't swap the call site... The result was the entire ATA blacklist was effectively disabled. The lesson for today is "I f***ed up *how* badly *how* many months ago?", er, I mean "Nobody Tests RC Kernels On Legacy Hardware". This was not a subtle break, but it made it through an entire RC cycle unreported, presumably because all the people doing testing have full-featured hardware. (FWIW, the reason for the argument swap was because fnmatch() does it that way, and for a while implementing a full fnmatch() was being considered.) Fixes: 428ac5fc056e0 (libata: Use glob_match from lib/glob.c) Reported-by: Steven Honeyman <stevenhoneyman@gmail.com> Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=71371#c21 Signed-off-by: George Spelvin <linux@horizon.com> Cc: <stable@vger.kernel.org> # 3.17 Tested-by: Steven Honeyman <stevenhoneyman@gmail.com> Signed-off-by: Tejun Heo <tj@kernel.org> 
lib/glob.c provides a new glob_match() function, with arguments in
(pattern, string) order.  It replaced a private function with arguments
in (string, pattern) order, but I didn't swap the call site...

The result was the entire ATA blacklist was effectively disabled.

The lesson for today is "I f***ed up *how* badly *how* many months ago?",
er, I mean "Nobody Tests RC Kernels On Legacy Hardware".

This was not a subtle break, but it made it through an entire RC
cycle unreported, presumably because all the people doing testing
have full-featured hardware.

(FWIW, the reason for the argument swap was because fnmatch() does it that
way, and for a while implementing a full fnmatch() was being considered.)

Fixes: 428ac5fc056e0 (libata: Use glob_match from lib/glob.c)
Reported-by: Steven Honeyman <stevenhoneyman@gmail.com>
Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=71371#c21
Signed-off-by: George Spelvin <linux@horizon.com>
Cc: <stable@vger.kernel.org> # 3.17
Tested-by: Steven Honeyman <stevenhoneyman@gmail.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
libata: change ata_<foo>_printk routines to return void 2014-09-23T14:02:31+00:00 Joe Perches joe@perches.com 2014-09-22T16:52:18+00:00 d7bead1b8890c3e47a24db270fdb840ea728d8f0 The return value is not used by callers of these functions nor by uses of all macros so change the functions to return void. Signed-off-by: Joe Perches <joe@perches.com> Signed-off-by: Tejun Heo <tj@kernel.org> 
The return value is not used by callers of these functions nor
by uses of all macros so change the functions to return void.

Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
libata: Use dev_name() for request_irq() to distinguish devices 2014-08-19T15:44:18+00:00 Alexander Shiyan shc_work@mail.ru 2014-08-19T06:51:04+00:00 4f37b504768c952b64bc9469a2d579c7597590f2 Use dev_name() instead of driver name for request_irq(). This will help to distinguish between multiple identical devices. Before: CPU0 5: 34425 clps711x-intc 5 pata_of_platform 6: 6778 clps711x-intc 6 pata_of_platform After: CPU0 5: 2182 clps711x-intc 5 20000000.ide 6: 11024 clps711x-intc 6 20100000.ide Signed-off-by: Alexander Shiyan <shc_work@mail.ru> Signed-off-by: Tejun Heo <tj@kernel.org> 
Use dev_name() instead of driver name for request_irq().
This will help to distinguish between multiple identical devices.

Before:
 CPU0
 5:      34425  clps711x-intc   5  pata_of_platform
 6:       6778  clps711x-intc   6  pata_of_platform

After:
 CPU0
 5:       2182  clps711x-intc   5  20000000.ide
 6:      11024  clps711x-intc   6  20100000.ide

Signed-off-by: Alexander Shiyan <shc_work@mail.ru>
Signed-off-by: Tejun Heo <tj@kernel.org>
libata: widen Crucial M550 blacklist matching 2014-08-18T21:40:09+00:00 Tejun Heo tj@kernel.org 2014-08-18T21:40:09+00:00 2a13772a144d2956a7fedd18685921d0a9b8b783 Crucial M550 may cause data corruption on queued trims and is blacklisted. The pattern used for it fails to match 1TB one as the capacity section will be four chars instead of three. Widen the pattern. Signed-off-by: Tejun Heo <tj@kernel.org> Reported-by: Charles Reiss <woggling@gmail.com> Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=81071 Cc: stable@vger.kernel.org 
Crucial M550 may cause data corruption on queued trims and is
blacklisted.  The pattern used for it fails to match 1TB one as the
capacity section will be four chars instead of three.  Widen the
pattern.

Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: Charles Reiss <woggling@gmail.com>
Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=81071
Cc: stable@vger.kernel.org
libata: Use glob_match from lib/glob.c 2014-08-07T01:01:25+00:00 George Spelvin linux@horizon.com 2014-08-06T23:09:27+00:00 428ac5fc056e06dc0b4ed82d5979add9a8c62b35 The function may be useful for other drivers, so export it. (Suggested by Tejun Heo.) Note that I inverted the return value of glob_match; returning true on match seemed to make more sense. Signed-off-by: George Spelvin <linux@horizon.com> Cc: Randy Dunlap <rdunlap@infradead.org> Cc: Tejun Heo <tj@kernel.org> Cc: Ingo Molnar <mingo@elte.hu> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> 
The function may be useful for other drivers, so export it.  (Suggested
by Tejun Heo.)

Note that I inverted the return value of glob_match; returning true on
match seemed to make more sense.

Signed-off-by: George Spelvin <linux@horizon.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
libata: introduce ata_host->n_tags to avoid oops on SAS controllers 2014-07-23T14:30:34+00:00 Tejun Heo tj@kernel.org 2014-07-23T13:05:27+00:00 1a112d10f03e83fb3a2fdc4c9165865dec8a3ca6 1871ee134b73 ("libata: support the ata host which implements a queue depth less than 32") directly used ata_port->scsi_host->can_queue from ata_qc_new() to determine the number of tags supported by the host; unfortunately, SAS controllers doing SATA don't initialize ->scsi_host leading to the following oops. BUG: unable to handle kernel NULL pointer dereference at 0000000000000058 IP: [<ffffffff814e0618>] ata_qc_new_init+0x188/0x1b0 PGD 0 Oops: 0002 [#1] SMP Modules linked in: isci libsas scsi_transport_sas mgag200 drm_kms_helper ttm CPU: 1 PID: 518 Comm: udevd Not tainted 3.16.0-rc6+ #62 Hardware name: Intel Corporation S2600CO/S2600CO, BIOS SE5C600.86B.02.02.0002.122320131210 12/23/2013 task: ffff880c1a00b280 ti: ffff88061a000000 task.ti: ffff88061a000000 RIP: 0010:[<ffffffff814e0618>] [<ffffffff814e0618>] ata_qc_new_init+0x188/0x1b0 RSP: 0018:ffff88061a003ae8 EFLAGS: 00010012 RAX: 0000000000000001 RBX: ffff88000241ca80 RCX: 00000000000000fa RDX: 0000000000000020 RSI: 0000000000000020 RDI: ffff8806194aa298 RBP: ffff88061a003ae8 R08: ffff8806194a8000 R09: 0000000000000000 R10: 0000000000000000 R11: ffff88000241ca80 R12: ffff88061ad58200 R13: ffff8806194aa298 R14: ffffffff814e67a0 R15: ffff8806194a8000 FS: 00007f3ad7fe3840(0000) GS:ffff880627620000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000000000058 CR3: 000000061a118000 CR4: 00000000001407e0 Stack: ffff88061a003b20 ffffffff814e96e1 ffff88000241ca80 ffff88061ad58200 ffff8800b6bf6000 ffff880c1c988000 ffff880619903850 ffff88061a003b68 ffffffffa0056ce1 ffff88061a003b48 0000000013d6e6f8 ffff88000241ca80 Call Trace: [<ffffffff814e96e1>] ata_sas_queuecmd+0xa1/0x430 [<ffffffffa0056ce1>] sas_queuecommand+0x191/0x220 [libsas] [<ffffffff8149afee>] scsi_dispatch_cmd+0x10e/0x300 [<ffffffff814a3bc5>] scsi_request_fn+0x2f5/0x550 [<ffffffff81317613>] __blk_run_queue+0x33/0x40 [<ffffffff8131781a>] queue_unplugged+0x2a/0x90 [<ffffffff8131ceb4>] blk_flush_plug_list+0x1b4/0x210 [<ffffffff8131d274>] blk_finish_plug+0x14/0x50 [<ffffffff8117eaa8>] __do_page_cache_readahead+0x198/0x1f0 [<ffffffff8117ee21>] force_page_cache_readahead+0x31/0x50 [<ffffffff8117ee7e>] page_cache_sync_readahead+0x3e/0x50 [<ffffffff81172ac6>] generic_file_read_iter+0x496/0x5a0 [<ffffffff81219897>] blkdev_read_iter+0x37/0x40 [<ffffffff811e307e>] new_sync_read+0x7e/0xb0 [<ffffffff811e3734>] vfs_read+0x94/0x170 [<ffffffff811e43c6>] SyS_read+0x46/0xb0 [<ffffffff811e33d1>] ? SyS_lseek+0x91/0xb0 [<ffffffff8171ee29>] system_call_fastpath+0x16/0x1b Code: 00 00 00 88 50 29 83 7f 08 01 19 d2 83 e2 f0 83 ea 50 88 50 34 c6 81 1d 02 00 00 40 c6 81 17 02 00 00 00 5d c3 66 0f 1f 44 00 00 <89> 14 25 58 00 00 00 Fix it by introducing ata_host->n_tags which is initialized to ATA_MAX_QUEUE - 1 in ata_host_init() for SAS controllers and set to scsi_host_template->can_queue in ata_host_register() for !SAS ones. As SAS hosts are never registered, this will give them the same ATA_MAX_QUEUE - 1 as before. Note that we can't use scsi_host->can_queue directly for SAS hosts anyway as they can go higher than the libata maximum. Signed-off-by: Tejun Heo <tj@kernel.org> Reported-by: Mike Qiu <qiudayu@linux.vnet.ibm.com> Reported-by: Jesse Brandeburg <jesse.brandeburg@gmail.com> Reported-by: Peter Hurley <peter@hurleysoftware.com> Reported-by: Peter Zijlstra <peterz@infradead.org> Tested-by: Alexey Kardashevskiy <aik@ozlabs.ru> Fixes: 1871ee134b73 ("libata: support the ata host which implements a queue depth less than 32") Cc: Kevin Hao <haokexin@gmail.com> Cc: Dan Williams <dan.j.williams@intel.com> Cc: stable@vger.kernel.org 
1871ee134b73 ("libata: support the ata host which implements a queue
depth less than 32") directly used ata_port->scsi_host->can_queue from
ata_qc_new() to determine the number of tags supported by the host;
unfortunately, SAS controllers doing SATA don't initialize ->scsi_host
leading to the following oops.

 BUG: unable to handle kernel NULL pointer dereference at 0000000000000058
 IP: [<ffffffff814e0618>] ata_qc_new_init+0x188/0x1b0
 PGD 0
 Oops: 0002 [#1] SMP
 Modules linked in: isci libsas scsi_transport_sas mgag200 drm_kms_helper ttm
 CPU: 1 PID: 518 Comm: udevd Not tainted 3.16.0-rc6+ #62
 Hardware name: Intel Corporation S2600CO/S2600CO, BIOS SE5C600.86B.02.02.0002.122320131210 12/23/2013
 task: ffff880c1a00b280 ti: ffff88061a000000 task.ti: ffff88061a000000
 RIP: 0010:[<ffffffff814e0618>]  [<ffffffff814e0618>] ata_qc_new_init+0x188/0x1b0
 RSP: 0018:ffff88061a003ae8  EFLAGS: 00010012
 RAX: 0000000000000001 RBX: ffff88000241ca80 RCX: 00000000000000fa
 RDX: 0000000000000020 RSI: 0000000000000020 RDI: ffff8806194aa298
 RBP: ffff88061a003ae8 R08: ffff8806194a8000 R09: 0000000000000000
 R10: 0000000000000000 R11: ffff88000241ca80 R12: ffff88061ad58200
 R13: ffff8806194aa298 R14: ffffffff814e67a0 R15: ffff8806194a8000
 FS:  00007f3ad7fe3840(0000) GS:ffff880627620000(0000) knlGS:0000000000000000
 CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
 CR2: 0000000000000058 CR3: 000000061a118000 CR4: 00000000001407e0
 Stack:
  ffff88061a003b20 ffffffff814e96e1 ffff88000241ca80 ffff88061ad58200
  ffff8800b6bf6000 ffff880c1c988000 ffff880619903850 ffff88061a003b68
  ffffffffa0056ce1 ffff88061a003b48 0000000013d6e6f8 ffff88000241ca80
 Call Trace:
  [<ffffffff814e96e1>] ata_sas_queuecmd+0xa1/0x430
  [<ffffffffa0056ce1>] sas_queuecommand+0x191/0x220 [libsas]
  [<ffffffff8149afee>] scsi_dispatch_cmd+0x10e/0x300
  [<ffffffff814a3bc5>] scsi_request_fn+0x2f5/0x550
  [<ffffffff81317613>] __blk_run_queue+0x33/0x40
  [<ffffffff8131781a>] queue_unplugged+0x2a/0x90
  [<ffffffff8131ceb4>] blk_flush_plug_list+0x1b4/0x210
  [<ffffffff8131d274>] blk_finish_plug+0x14/0x50
  [<ffffffff8117eaa8>] __do_page_cache_readahead+0x198/0x1f0
  [<ffffffff8117ee21>] force_page_cache_readahead+0x31/0x50
  [<ffffffff8117ee7e>] page_cache_sync_readahead+0x3e/0x50
  [<ffffffff81172ac6>] generic_file_read_iter+0x496/0x5a0
  [<ffffffff81219897>] blkdev_read_iter+0x37/0x40
  [<ffffffff811e307e>] new_sync_read+0x7e/0xb0
  [<ffffffff811e3734>] vfs_read+0x94/0x170
  [<ffffffff811e43c6>] SyS_read+0x46/0xb0
  [<ffffffff811e33d1>] ? SyS_lseek+0x91/0xb0
  [<ffffffff8171ee29>] system_call_fastpath+0x16/0x1b
 Code: 00 00 00 88 50 29 83 7f 08 01 19 d2 83 e2 f0 83 ea 50 88 50 34 c6 81 1d 02 00 00 40 c6 81 17 02 00 00 00 5d c3 66 0f 1f 44 00 00 <89> 14 25 58 00 00 00

Fix it by introducing ata_host->n_tags which is initialized to
ATA_MAX_QUEUE - 1 in ata_host_init() for SAS controllers and set to
scsi_host_template->can_queue in ata_host_register() for !SAS ones.
As SAS hosts are never registered, this will give them the same
ATA_MAX_QUEUE - 1 as before.  Note that we can't use
scsi_host->can_queue directly for SAS hosts anyway as they can go
higher than the libata maximum.

Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: Mike Qiu <qiudayu@linux.vnet.ibm.com>
Reported-by: Jesse Brandeburg <jesse.brandeburg@gmail.com>
Reported-by: Peter Hurley <peter@hurleysoftware.com>
Reported-by: Peter Zijlstra <peterz@infradead.org>
Tested-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Fixes: 1871ee134b73 ("libata: support the ata host which implements a queue depth less than 32")
Cc: Kevin Hao <haokexin@gmail.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: stable@vger.kernel.org