Merge tag 'xfs-for-linus-4.9-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/dgc/linux-xfs

Pull xfs and iomap updates from Dave Chinner:
 "The main things in this update are the iomap-based DAX infrastructure,
  an XFS delalloc rework, and a chunk of fixes to how log recovery
  schedules writeback to prevent spurious corruption detections when
  recovery of certain items was not required.

  The other main chunk of code is some preparation for the upcoming
  reflink functionality. Most of it is generic and cleanups that stand
  alone, but they were ready and reviewed so are in this pull request.

  Speaking of reflink, I'm currently planning to send you another pull
  request next week containing all the new reflink functionality. I'm
  working through a similar process to the last cycle, where I sent the
  reverse mapping code in a separate request because of how large it
  was. The reflink code merge is even bigger than reverse mapping, so
  I'll be doing the same thing again....

  Summary for this update:

   - change of XFS mailing list to linux-xfs@vger.kernel.org

   - iomap-based DAX infrastructure w/ XFS and ext2 support

   - small iomap fixes and additions

   - more efficient XFS delayed allocation infrastructure based on iomap

   - a rework of log recovery writeback scheduling to ensure we don't
     fail recovery when trying to replay items that are already on disk

   - some preparation patches for upcoming reflink support

   - configurable error handling fixes and documentation

   - aio access time update race fixes for XFS and
     generic_file_read_iter"

* tag 'xfs-for-linus-4.9-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/dgc/linux-xfs: (40 commits)
  fs: update atime before I/O in generic_file_read_iter
  xfs: update atime before I/O in xfs_file_dio_aio_read
  ext2: fix possible integer truncation in ext2_iomap_begin
  xfs: log recovery tracepoints to track current lsn and buffer submission
  xfs: update metadata LSN in buffers during log recovery
  xfs: don't warn on buffers not being recovered due to LSN
  xfs: pass current lsn to log recovery buffer validation
  xfs: rework log recovery to submit buffers on LSN boundaries
  xfs: quiesce the filesystem after recovery on readonly mount
  xfs: remote attribute blocks aren't really userdata
  ext2: use iomap to implement DAX
  ext2: stop passing buffer_head to ext2_get_blocks
  xfs: use iomap to implement DAX
  xfs: refactor xfs_setfilesize
  xfs: take the ilock shared if possible in xfs_file_iomap_begin
  xfs: fix locking for DAX writes
  dax: provide an iomap based fault handler
  dax: provide an iomap based dax read/write path
  dax: don't pass buffer_head to copy_user_dax
  dax: don't pass buffer_head to dax_insert_mapping
  ...

1 files changed, 123 insertions, 0 deletions

diff --git a/Documentation/filesystems/xfs.txt b/Documentation/filesystems/xfs.txt
index 8146e9fd5ffc..c2d44e6e117b 100644
--- a/Documentation/filesystems/xfs.txt
+++ b/Documentation/filesystems/xfs.txt
@@ -348,3 +348,126 @@ Removed Sysctls
   ----				-------
   fs.xfs.xfsbufd_centisec	v4.0
   fs.xfs.age_buffer_centisecs	v4.0
+
+
+Error handling
+==============
+
+XFS can act differently according to the type of error found during its
+operation. The implementation introduces the following concepts to the error
+handler:
+
+ -failure speed:
+	Defines how fast XFS should propagate an error upwards when a specific
+	error is found during the filesystem operation. It can propagate
+	immediately, after a defined number of retries, after a set time period,
+	or simply retry forever.
+
+ -error classes:
+	Specifies the subsystem the error configuration will apply to, such as
+	metadata IO or memory allocation. Different subsystems will have
+	different error handlers for which behaviour can be configured.
+
+ -error handlers:
+	Defines the behavior for a specific error.
+
+The filesystem behavior during an error can be set via sysfs files. Each
+error handler works independently - the first condition met by an error handler
+for a specific class will cause the error to be propagated rather than reset and
+retried.
+
+The action taken by the filesystem when the error is propagated is context
+dependent - it may cause a shut down in the case of an unrecoverable error,
+it may be reported back to userspace, or it may even be ignored because
+there's nothing useful we can with the error or anyone we can report it to (e.g.
+during unmount).
+
+The configuration files are organized into the following hierarchy for each
+mounted filesystem:
+
+  /sys/fs/xfs/<dev>/error/<class>/<error>/
+
+Where:
+  <dev>
+	The short device name of the mounted filesystem. This is the same device
+	name that shows up in XFS kernel error messages as "XFS(<dev>): ..."
+
+  <class>
+	The subsystem the error configuration belongs to. As of 4.9, the defined
+	classes are:
+
+		- "metadata": applies metadata buffer write IO
+
+  <error>
+	The individual error handler configurations.
+
+
+Each filesystem has "global" error configuration options defined in their top
+level directory:
+
+  /sys/fs/xfs/<dev>/error/
+
+  fail_at_unmount		(Min:  0  Default:  1  Max: 1)
+	Defines the filesystem error behavior at unmount time.
+
+	If set to a value of 1, XFS will override all other error configurations
+	during unmount and replace them with "immediate fail" characteristics.
+	i.e. no retries, no retry timeout. This will always allow unmount to
+	succeed when there are persistent errors present.
+
+	If set to 0, the configured retry behaviour will continue until all
+	retries and/or timeouts have been exhausted. This will delay unmount
+	completion when there are persistent errors, and it may prevent the
+	filesystem from ever unmounting fully in the case of "retry forever"
+	handler configurations.
+
+	Note: there is no guarantee that fail_at_unmount can be set whilst an
+	unmount is in progress. It is possible that the sysfs entries are
+	removed by the unmounting filesystem before a "retry forever" error
+	handler configuration causes unmount to hang, and hence the filesystem
+	must be configured appropriately before unmount begins to prevent
+	unmount hangs.
+
+Each filesystem has specific error class handlers that define the error
+propagation behaviour for specific errors. There is also a "default" error
+handler defined, which defines the behaviour for all errors that don't have
+specific handlers defined. Where multiple retry constraints are configuredi for
+a single error, the first retry configuration that expires will cause the error
+to be propagated. The handler configurations are found in the directory:
+
+  /sys/fs/xfs/<dev>/error/<class>/<error>/
+
+  max_retries			(Min: -1  Default: Varies  Max: INTMAX)
+	Defines the allowed number of retries of a specific error before
+	the filesystem will propagate the error. The retry count for a given
+	error context (e.g. a specific metadata buffer) is reset every time
+	there is a successful completion of the operation.
+
+	Setting the value to "-1" will cause XFS to retry forever for this
+	specific error.
+
+	Setting the value to "0" will cause XFS to fail immediately when the
+	specific error is reported.
+
+	Setting the value to "N" (where 0 < N < Max) will make XFS retry the
+	operation "N" times before propagating the error.
+
+  retry_timeout_seconds		(Min:  -1  Default:  Varies  Max: 1 day)
+	Define the amount of time (in seconds) that the filesystem is
+	allowed to retry its operations when the specific error is
+	found.
+
+	Setting the value to "-1" will allow XFS to retry forever for this
+	specific error.
+
+	Setting the value to "0" will cause XFS to fail immediately when the
+	specific error is reported.
+
+	Setting the value to "N" (where 0 < N < Max) will allow XFS to retry the
+	operation for up to "N" seconds before propagating the error.
+
+Note: The default behaviour for a specific error handler is dependent on both
+the class and error context. For example, the default values for
+"metadata/ENODEV" are "0" rather than "-1" so that this error handler defaults
+to "fail immediately" behaviour. This is done because ENODEV is a fatal,
+unrecoverable error no matter how many times the metadata IO is retried.