This adds an API to wait for pending commit callbacks of already-synced
transactions to finish processing. This is needed by the DMU-OSD in
Lustre during device finalization when some callbacks may still not be
called, this leads to non-zero reference count errors. See lustre.org
bug 23931.
The new prefered inteface for evicting an inode from the inode cache
is the ->evict_inode() callback. It replaces both the ->delete_inode()
and ->clear_inode() callbacks which were previously used for this.
The xattr handler prototypes were sanitized with the idea being that
the same handlers could be used for multiple methods. The result of
this was the inode type was changes to a dentry, and both the get()
and set() hooks had a handler_flags argument added. The list()
callback was similiarly effected but no autoconf check was added
because we do not use the list() callback.
The fsync() callback in the file_operations structure used to take
3 arguments. The callback now only takes 2 arguments because the
dentry argument was determined to be unused by all consumers. To
handle this a compatibility prototype was added to ensure the right
prototype is used. Our implementation never used the dentry argument
either so it's just a matter of using the right prototype.
The const keyword was added to the 'struct xattr_handler' in the
generic Linux super_block structure. To handle this we define an
appropriate xattr_handler_t typedef which can be used. This was
the preferred solution because it keeps the code clean and readable.
Initial testing has shown the the right IO scheduler to use under Linux
is noop. This strikes the ideal balance by allowing the zfs elevator
to do all request ordering and prioritization. While allowing the
Linux elevator to do the maximum front/back merging allowed by the
physical device. This yields the largest possible requests for the
device with the lowest total overhead.
While 'noop' should be right for your system you can choose a different
IO scheduler with the 'zfs_vdev_scheduler' option. You may set this
value to any of the standard Linux schedulers: noop, cfq, deadline,
anticipatory. In addition, if you choose 'none' zfs will not attempt
to change the IO scheduler for the block device.
It's worth taking a moment to describe how mmap is implemented
for zfs because it differs considerably from other Linux filesystems.
However, this issue is handled the same way under OpenSolaris.
The issue is that by design zfs bypasses the Linux page cache and
leaves all caching up to the ARC. This has been shown to work
well for the common read(2)/write(2) case. However, mmap(2)
is problem because it relies on being tightly integrated with the
page cache. To handle this we cache mmap'ed files twice, once in
the ARC and a second time in the page cache. The code is careful
to keep both copies synchronized.
When a file with an mmap'ed region is written to using write(2)
both the data in the ARC and existing pages in the page cache
are updated. For a read(2) data will be read first from the page
cache then the ARC if needed. Neither a write(2) or read(2) will
will ever result in new pages being added to the page cache.
New pages are added to the page cache only via .readpage() which
is called when the vfs needs to read a page off disk to back the
virtual memory region. These pages may be modified without
notifying the ARC and will be written out periodically via
.writepage(). This will occur due to either a sync or the usual
page aging behavior. Note because a read(2) of a mmap'ed file
will always check the page cache first even when the ARC is out
of date correct data will still be returned.
While this implementation ensures correct behavior it does have
have some drawbacks. The most obvious of which is that it
increases the required memory footprint when access mmap'ed
files. It also adds additional complexity to the code keeping
both caches synchronized.
Longer term it may be possible to cleanly resolve this wart by
mapping page cache pages directly on to the ARC buffers. The
Linux address space operations are flexible enough to allow
selection of which pages back a particular index. The trick
would be working out the details of which subsystem is in
charge, the ARC, the page cache, or both. It may also prove
helpful to move the ARC buffers to a scatter-gather lists
rather than a vmalloc'ed region.
Additionally, zfs_write/read_common() were used in the readpage
and writepage hooks because it was fairly easy. However, it
would be better to update zfs_fillpage and zfs_putapage to be
Linux friendly and use them instead.
The Linux specific file operations have all been located in the
file zpl_file.c. These functions primarily rely on the reworked
zfs_* functions to do their job. They are also responsible for
converting the possible Solaris style error codes to negative
Linux errors.
This first zpl_* commit also includes a common zpl.h header with
minimal entries to register the Linux specific hooks. In also
adds all the new zpl_* file to the Makefile.in. This is not a
standalone commit, you required the following zpl_* commits.
A new flag is required for the zfs_rlock code to determine if
it is operation of the zvol of zpl dataset. This used to be
keyed off the zp->z_vnode, which was a hack to begin with, but
with the removal of vnodes we needed a dedicated flag.
I appologize in advance why to many things ended up in this commit.
When it could be seperated in to a whole series of commits teasing
that all apart now would take considerable time and I'm not sure
there's much merrit in it. As such I'll just summerize the intent
of the changes which are all (or partly) in this commit. Broadly
the intent is to remove as much Solaris specific code as possible
and replace it with native Linux equivilants. More specifically:
1) Replace all instances of zfsvfs_t with zfs_sb_t. While the
type is largely the same calling it private super block data
rather than a zfsvfs is more consistent with how Linux names
this. While non critical it makes the code easier to read when
your thinking in Linux friendly VFS terms.
2) Replace vnode_t with struct inode. The Linux VFS doesn't have
the notion of a vnode and there's absolutely no good reason to
create one. There are in fact several good reasons to remove it.
It just adds overhead on Linux if we were to manage one, it
conplicates the code, and it likely will lead to bugs so there's
a good change it will be out of date. The code has been updated
to remove all need for this type.
3) Replace all vtype_t's with umode types. Along with this shift
all uses of types to mode bits. The Solaris code would pass a
vtype which is redundant with the Linux mode. Just update all the
code to use the Linux mode macros and remove this redundancy.
4) Remove using of vn_* helpers and replace where needed with
inode helpers. The big example here is creating iput_aync to
replace vn_rele_async. Other vn helpers will be addressed as
needed but they should be be emulated. They are a Solaris VFS'ism
and should simply be replaced with Linux equivilants.
5) Update znode alloc/free code. Under Linux it's common to
embed the inode specific data with the inode itself. This removes
the need for an extra memory allocation. In zfs this information
is called a znode and it now embeds the inode with it. Allocators
have been updated accordingly.
6) Minimal integration with the vfs flags for setting up the
super block and handling mount options has been added this
code will need to be refined but functionally it's all there.
This will be the first and last of these to large to review commits.
For the moment we do not use dmu_write_pages() to write pages
directly in to a dmu object. It may be required at some point
in the future, but for now is simplest and cleanest to drop it.
It can be easily readded if/when needed.
This code is used for snapshot and heavily leverages Solaris
functionality we do not want to reimplement. These files have
been removed, including references to them, and will be replaced
by a zfs_snap.c/zpl_snap.c implementation which handles snapshots.
For the moment we have left ZFS unchanged and it updates many values
as part of the znode. However, some of these values should be set
in the inode. For the moment this is handled by adding a function
called zfs_inode_update() which updates the inode based on the znode.
This is considered a workaround until we can systematically go
through the ZFS code and have it directly update the inode. At
which point zfs_update_inode() can be dropped entirely. Keeping
two copies of the same data isn't only inefficient it's a breeding
ground for bugs.
Under Linux the convention for filesystem specific data structure is
to embed it along with the generic vfs data structure. This differs
significantly from Solaris.
Since we want to integrates as cleanly with the Linux VFS as possible.
This changes modifies zfs_znode_alloc() to allocate a znode with an
embedded inode for use with the generic VFS. This is done by calling
iget_locked() which will allocate a new inode if needed by calling
sb->alloc_inode(). This function allocates enough memory for a
znode_t by returns a pointer to the inode structure for Linux's VFS.
This function is also responsible for setting the callback
znode->z_set_ops_inodes() which is used to register the correct
handlers for the inode.
Lay the initial ground work for a include/linux/ compatibility
directory. This was less critical in the past because the bulk
of the ZFS code consumes the Solaris API via the SPL. This API
was stable and the bulk Linux API differences were handled in
the SPL.
However, with the addition of a full Posix layer written directly
against the Linux APIs we are going to need more compatibility
code. It makes sense that all this code should be cleanly located
in one place. Subsequent patches should move the existing zvol
and vdev_disk compatibility code in to this directory.
This code originates in OpenSolaris and was modified by KQ Infotech
to be compatible with Linux. While supporting uios in the short
term is useful to get something working this is not an abstraction
we want to keep. This code is expected to be short lived and
removed as soon as all the remaining uio based APIs and updated.
These functions were dropped originally because I felt they would
need to be rewritten anyway to avoid using uios. However, this
patch readds then with they dea they can just be reworked and
the uio bits dropped.
ZFS even under Solaris does not strictly require libshare to be
available. The current implementation attempts to dlopen() the
library to access the needed symbols. If this fails libshare
support is simply disabled.
This means that on Linux we only need the most minimal libshare
implementation. In fact just enough to prevent the build from
failing. Longer term we can decide if we want to implement a
libshare library like Solaris. At best this would be an abstraction
layer between ZFS and NFS/SMB. Alternately, we can drop libshare
entirely and directly integrate ZFS with Linux's NFS/SMB.
Finally the bare bones user-libshare.m4 test was dropped. If we
do decide to implement libshare at some point it will surely be
as part of this package so the check is not needed.
Previously we would ASSERT in cv_destroy() if it was ever called
with active waiters. However, I've now seen several instances in
OpenSolaris code where they do the following:
cv_broadcast();
cv_destroy();
This leaves no time for active waiters to be woken up and scheduled
and we trip the ASSERT. This has not been observed to be an issue
on OpenSolaris because their cv_destroy() basically does nothing.
They still do run the risk of the memory being free'd after the
cv_destroy() and hitting a bad paging request. But in practice
this race is so small and unlikely it either doesn't happen, or
is so unlikely when it does happen the root cause has not yet been
identified.
Rather than risk the same issue in our code this change updates
cv_destroy() to block until all waiters have been woken and
scheduled. This may take some time because each waiter must
acquire the mutex.
This change may have an impact on performance for frequently
created and destroyed condition variables. That however is a price
worth paying it avoid crashing your system. If performance issues
are observed they can be addressed by the caller.
Recently helper functions were added to libzfs_util to load a kernel
module or execute a process. Initially this functionality was limited
to libzfs but it has become clear there will be other consumers. This
change opens up the interface so it may be used where appropriate.
If libselinux is detected on your system at configure time link
against it. This allows us to use a library call to detect if
selinux is enabled and if it is to pass the mount option:
"context=\"system_u:object_r:file_t:s0"
For now this is required because none of the existing selinux
policies are aware of the zfs filesystem type. Because of this
they do not properly enable xattr based labeling even though
zfs supports all of the required hooks.
Until distro's add zfs as a known xattr friendly fs type we
must use mntpoint labeling. Alternately, end users could modify
their existing selinux policy with a little guidance.
Simply add the policy function wrappers. They are completely
non-functional and always return that everything is OK, but once
again they simplify compilation of dependent packages for now.
These can/should be removed once the security policy of the
dependent application is completely understood and intergrade
as appropriate with Linux.
Dependent packages require the following missing headers to
simplify compilation. The headers are basically just stubbed
out with minimal content required.
The following flags are use to get the proper mask when getting
and setting ACLs. I'm hopeful this can all largely go away at
some point.
We also add a define for the maximum number of ACL entries.
MAX_ACL_ENTRIES is used as the maximum number of entries for
each type.
For Linux the maximum uid can vary depending on how your kernel
is built. The Linux kernel still can be compiled with 16 but uids
and gids, although I'm not aware of a major distribution which does
this (maybe an embedded one?). Given that caviot it is reasonably
safe to define the MAXUID as 2147483647.
This patch simply removes the place holder vfs_t type and includes
some generic Linux VFS headers. It also makes some minor fid_t
additions for compatibility.
Previously these were defined to noops but rather than give
the misleading impression that these are actually implemented
I'm removing the type entirely for clarity.
The cv_timedwait() function by definition must wait unconditionally
for cv_signal()/cv_broadcast() before waking. This causes processes
to go in the D state which increases the load average. The load
average is the summation of processes in D state and run queue.
To avoid this it can be desirable to sleep interruptibly. These
processes do not count against the load average but may be woken by
a signal. It is up to the caller to determine why the process
was woken it may be for one of three reasons.
1) cv_signal()/cv_broadcast()
2) the timeout expired
3) a signal was received
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Create spl_inode_lock/spl_inode_unlock compability macros to simply
access to the inode mutex/sem. This avoids the need to have to ugly
up the code with the required #define's at every call site. At the
moment the SPL only uses this in one place but higher layers can
benefit from the macro.
The issue is that cv_timedwait() sleeps uninterruptibly to block signals
and avoid waking up early. Under Linux this counts against the load
average keeping it artificially high. This change allows the arc to
sleep interruptibly which mean it may be woken up early due to a signal.
Normally this means some extra care must be taken to handle a potential
signal. But for the arcs usage of cv_timedwait() there is no harm in
waking up before the timeout expires so no extra handling is required.
Thread specific data has implemented using a hash table, this avoids
the need to add a member to the task structure and allows maximum
portability between kernels. This implementation has been optimized
to keep the tsd_set() and tsd_get() times as small as possible.
The majority of the entries in the hash table are for specific tsd
entries. These entries are hashed by the product of their key and
pid because by design the key and pid are guaranteed to be unique.
Their product also has the desirable properly that it will be uniformly
distributed over the hash bins providing neither the pid nor key is zero.
Under linux the zero pid is always the init process and thus won't be
used, and this implementation is careful to never to assign a zero key.
By default the hash table is sized to 512 bins which is expected to
be sufficient for light to moderate usage of thread specific data.
The hash table contains two additional type of entries. They first
type is entry is called a 'key' entry and it is added to the hash during
tsd_create(). It is used to store the address of the destructor function
and it is used as an anchor point. All tsd entries which use the same
key will be linked to this entry. This is used during tsd_destory() to
quickly call the destructor function for all tsd associated with the key.
The 'key' entry may be looked up with tsd_hash_search() by passing the
key you wish to lookup and DTOR_PID constant as the pid.
The second type of entry is called a 'pid' entry and it is added to the
hash the first time a process set a key. The 'pid' entry is also used
as an anchor and all tsd for the process will be linked to it. This
list is using during tsd_exit() to ensure all registered destructors
are run for the process. The 'pid' entry may be looked up with
tsd_hash_search() by passing the PID_KEY constant as the key, and
the process pid. Note that tsd_exit() is called by thread_exit()
so if your using the Solaris thread API you should not need to call
tsd_exit() directly.
When HAVE_MUTEX_OWNER and CONFIG_SMP are defined, kmutex_t is just
a typedef for struct mutex.
This is generally OK but has the downside that it can make mistakes
such as mutex_lock(&kmutex_var) to pass by unnoticed until someone
compiles the code without HAVE_MUTEX_OWNER or CONFIG_SMP (in which
case kmutex_t is a real struct). Note that the correct API to call
should have been mutex_enter() rather than mutex_lock().
We prevent these kind of mistakes by making kmutex_t a real structure
with only one field. This makes kmutex_t typesafe and it shouldn't
have any impact on the generated assembly code.
Signed-off-by: Ricardo M. Correia <ricardo.correia@oracle.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
For debugging purposes the condition varaibles keep track of the
mutex used during a wait. The idea is to validate that all callers
always use the same mutex. Unfortunately, we have seen cases where
the caller reuses the condition variable with a different mutex but
in a way which is known to be safe. My reading of the man pages
suggests you should not do this and always cv_destroy()/cv_init()
a new mutex. However, there is overhead in doing this and it does
appear to be allowed under Solaris.
To accomidate this behavior cv_wait_common() and __cv_timedwait()
have been modified to clear the associated mutex when the last
waiter is dropped. This ensures that while the condition variable
is in use the incorrect mutex case is detected. It also allows the
condition variable to be safely recycled without requiring the
overhead of a cv_destroy()/cv_init() as long as it isn't currently
in use.
Finally, spin lock cv->cv_lock was removed because it is not required.
When the condition variable is used properly the caller will always
be holding the mutex so the spin lock is redundant. The lock was
originally added because I expected to need to protect more than
just the cv->cv_mutex. It turns out that was not the case.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Most of the blk_* macros were removed in 2.6.36. Ostensibly this was
done to improve readability and allow easier grepping. However, from
a portability stand point the macros are helpful. Therefore the needed
macros are redefined here if they are missing from the kernel.
The name of the flag used to mark a bio as synchronous has changed
again in the 2.6.36 kernel due to the unification of the BIO_RW_*
and REQ_* flags. The new flag is called REQ_SYNC. To simplify
checking this flag I have introduced the vdev_disk_dio_is_sync()
helper function. Based on the results of several new autoconf
tests it uses the correct mask to check for a synchronous bio.
Preferred interface for flagging a synchronous bio:
2.6.12-2.6.29: BIO_RW_SYNC
2.6.30-2.6.35: BIO_RW_SYNCIO
2.6.36-2.6.xx: REQ_SYNC
As of linux-2.6.36 the BIO_RW_FAILFAST and REQ_FAILFAST flags
have been unified under the REQ_* names. These flags always had
to be kept in-sync so this is a nice step forward, unfortunately
it means we need to be careful to only use the new unified flags
when the BIO_RW_* flags are not defined. Additional autoconf
checks were added for this and if it is ever unclear which method
to use no flags are set. This is safe but may result in longer
delays before a disk is failed.
Perferred interface for setting FAILFAST on a bio:
2.6.12-2.6.27: BIO_RW_FAILFAST
2.6.28-2.6.35: BIO_RW_FAILFAST_{DEV|TRANSPORT|DRIVER}
2.6.36-2.6.xx: REQ_FAILFAST_{DEV|TRANSPORT|DRIVER}
The ZFS module returns ENOTSUP for several error conditions where an operation
is not (yet) supported. The SPL defined ENOTSUP in terms of ENOTSUPP, but that
is an internal Linux kernel error code that should not be seen by user
programs. As a result the zfs utilities print a confusing error message if an
unsupported operation is attempted:
internal error: Unknown error 524
Aborted
This change defines ENOTSUP in terms of EOPNOTSUPP which is consistent with
user space.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
As of linux-2.6.36 RLIM64_INFINITY is defined in linux/resource.h.
This is handled by conditionally defining RLIM64_INFINITY in the
SPL only when the kernel does not provide it.
It's important to clear mp->owner after calling mutex_unlock()
because when CONFIG_DEBUG_MUTEXES is defined the mutex owner
is verified in mutex_unlock(). If we set it to NULL this check
fails and the lockdep support is immediately disabled.
This change adds two helper functions for working with vdev names and paths.
zfs_resolve_shortname() resolves a shorthand vdev name to an absolute path
of a file in /dev, /dev/disk/by-id, /dev/disk/by-label, /dev/disk/by-path,
/dev/disk/by-uuid, /dev/disk/zpool. This was previously done only in the
function is_shorthand_path(), but we need a general helper function to
implement shorthand names for additional zpool subcommands like remove.
is_shorthand_path() is accordingly updated to call the helper function.
There is a minor change in the way zfs_resolve_shortname() tests if a file
exists. is_shorthand_path() effectively used open() and stat64() to test for
file existence, since its scope includes testing if a device is a whole disk
and collecting file status information. zfs_resolve_shortname(), on the other
hand, only uses access() to test for existence and leaves it to the caller to
perform any additional file operations. This seemed like the most general and
lightweight approach, and still preserves the semantics of is_shorthand_path().
zfs_append_partition() appends a partition suffix to a device path. This
should be used to generate the name of a whole disk as it is stored in the vdev
label. The user-visible names of whole disks do not contain the partition
information, while the name in the vdev label does. The code was lifted from
the function make_disks(), which now just calls the helper function. Again,
having a helper function to do this supports general handling of shorthand
names in the user interface.
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
It turns out that 'zpool events' over 1024 bytes in size where being
silently dropped. This was discovered while writing the zfault.sh
tests to validate common failure modes.
This could occur because the zfs interface for passing an arbitrary
size nvlist_t over an ioctl() is to provide a buffer for the packed
nvlist which is usually big enough. In this case 1024 byte is the
default. If the kernel determines the buffer is to small it returns
ENOMEM and the minimum required size of the nvlist_t. This was
working properly but in the case of 'zpool events' the event stream
was advanced dispite the error. Thus the retry with the bigger
buffer would succeed but it would skip over the previous event.
The fix is to pass this size to zfs_zevent_next() and determine
before removing the event from the list if it will fit. This was
preferable to checking after the event was returned because this
avoids the need to rewind the stream.
While there is no right maximum timeout for a disk IO we can start
laying the ground work to measure how long they do take in practice.
This change simply measures the IO time and if it exceeds 30s an
event is posted for 'zpool events'.
This value was carefully selected because for sd devices it implies
that at least one timeout (SD_TIMEOUT) has occured. Unfortunately,
even with FAILFAST set we may retry and request and not get an
error. This behavior is strongly dependant on the device driver
and how it is hooked in to the scsi error handling stack. However
by setting the limit at 30s we can log the event even if no error
was returned.
Slightly longer term we can start recording these delays perhaps
as a simple power-of-two histrogram. This histogram can then be
reported as part of the 'zpool status' command when given an command
line option.
None of this code changes the internal behavior of ZFS. Currently
it is simply for reporting excessively long delays.
Ricardo M. Correia