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Niklas Cassel 8e59a2a545 ata: libata: Set DID_TIME_OUT for commands that actually timed out 
When ata_qc_complete() schedules a command for EH using
ata_qc_schedule_eh(), blk_abort_request() will be called, which leads to
req->q->mq_ops->timeout() / scsi_timeout() being called.

scsi_timeout(), if the LLDD has no abort handler (libata has no abort
handler), will set host byte to DID_TIME_OUT, and then call
scsi_eh_scmd_add() to add the command to EH.

Thus, when commands first enter libata's EH strategy_handler, all the
commands that have been added to EH will have DID_TIME_OUT set.

Commit e5dd410acb ("ata: libata: Clear DID_TIME_OUT for ATA PT commands
with sense data") clears this bogus DID_TIME_OUT flag for all commands
that reached libata's EH strategy_handler.

libata has its own flag (AC_ERR_TIMEOUT), that it sets for commands that
have not received a completion at the time of entering EH.

ata_eh_worth_retry() has no special handling for AC_ERR_TIMEOUT, so by
default timed out commands will get flag ATA_QCFLAG_RETRY set, and will be
retried after the port has been reset (ata_eh_link_autopsy() always
triggers a port reset if any command has AC_ERR_TIMEOUT set).

For a command that has ATA_QCFLAG_RETRY set, while also having an error
flag set (e.g. AC_ERR_TIMEOUT), ata_eh_finish() will not increment
scmd->allowed, so the command will at most be retried scmd->allowed number
of times (which by default is set to 3).

However, scsi_eh_flush_done_q() will only retry commands for which
scsi_noretry_cmd() returns false.

For a command that has DID_TIME_OUT set, while also having either the
FAILFAST flag set, or the command being a passthrough command,
scsi_noretry_cmd() will return true. Thus, such a command will never be
retried.

Thus, make sure that libata sets SCSI's DID_TIME_OUT flag for commands that
actually timed out (libata's AC_ERR_TIMEOUT flag), such that timed out
commands will once again not be retried if they are also a FAILFAST or
passthrough command.

Cc: stable@vger.kernel.org
Fixes: e5dd410acb ("ata: libata: Clear DID_TIME_OUT for ATA PT commands with sense data")
Reported-by: Lai, Yi <yi1.lai@linux.intel.com>
Closes: https://lore.kernel.org/linux-ide/ZxYz871I3Blsi30F@ly-workstation/
Reviewed-by: Damien Le Moal <dlemoal@kernel.org>
Link: https://lore.kernel.org/r/20241023105540.1070012-2-cassel@kernel.org
Signed-off-by: Niklas Cassel <cassel@kernel.org>
History 2024-10-24 11:14:00 +02:00
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README 

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.