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I found a race involving the larp control knob, aka the debugging knob
that lets developers enable logging of extended attribute updates:
Thread 1 Thread 2
echo 0 > /sys/fs/xfs/debug/larp
setxattr(REPLACE)
xfs_has_larp (returns false)
xfs_attr_set
echo 1 > /sys/fs/xfs/debug/larp
xfs_attr_defer_replace
xfs_attr_init_replace_state
xfs_has_larp (returns true)
xfs_attr_init_remove_state
<oops, wrong DAS state!>
This isn't a particularly severe problem right now because xattr logging
is only enabled when CONFIG_XFS_DEBUG=y, and developers *should* know
what they're doing.
However, the eventual intent is that callers should be able to ask for
the assistance of the log in persisting xattr updates. This capability
might not be required for /all/ callers, which means that dynamic
control must work correctly. Once an xattr update has decided whether
or not to use logged xattrs, it needs to stay in that mode until the end
of the operation regardless of what subsequent parallel operations might
do.
Therefore, it is an error to continue sampling xfs_globals.larp once
xfs_attr_change has made a decision about larp, and it was not correct
for me to have told Allison that ->create_intent functions can sample
the global log incompat feature bitfield to decide to elide a log item.
Instead, create a new op flag for the xfs_da_args structure, and convert
all other callers of xfs_has_larp and xfs_sb_version_haslogxattrs within
the attr update state machine to look for the operations flag.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
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While running xfs/297 and generic/642, I noticed a crash in
xfs_attri_item_relog when it tries to copy the attr name to the new
xattri log item. I think what happened here was that we called
->iop_commit on the old attri item (which nulls out the pointers) as
part of a log force at the same time that a chained attr operation was
ongoing. The system was busy enough that at some later point, the defer
ops operation decided it was necessary to relog the attri log item, but
as we've detached the name buffer from the old attri log item, we can't
copy it to the new one, and kaboom.
I think there's a broader refcounting problem with LARP mode -- the
setxattr code can return to userspace before the CIL actually formats
and commits the log item, which results in a UAF bug. Therefore, the
xattr log item needs to be able to retain a reference to the name and
value buffers until the log items have completely cleared the log.
Furthermore, each time we create an intent log item, we allocate new
memory and (re)copy the contents; sharing here would be very useful.
Solve the UAF and the unnecessary memory allocations by having the log
code create a single refcounted buffer to contain the name and value
contents. This buffer can be passed from old to new during a relog
operation, and the logging code can (optionally) attach it to the
xfs_attr_item for reuse when LARP mode is enabled.
This also fixes a problem where the xfs_attri_log_item objects weren't
being freed back to the same cache where they came from.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
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Clean up the following includecheck warning:
./fs/xfs/xfs_attr_item.c: xfs_inode.h is included more than once.
Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Signed-off-by: Jiapeng Chong <jiapeng.chong@linux.alibaba.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Dave Chinner <david@fromorbit.com>
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Everywhere else in XFS, structures that capture the state of an ongoing
deferred work item all have names that end with "_intent". The new
extended attribute deferred work items are not named as such, so fix it
to follow the naming convention used elsewhere.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
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Initialize and destroy the xattr log item caches in the same places that
we do all the other log item caches.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
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Create a separate slab cache for struct xfs_attr_item objects, since we
can pack the (104-byte) intent items more tightly than we can with the
general slab cache objects. On x86, this means 39 intents per memory
page instead of 32.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
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The flags that are stored in the extended attr intent log item really
should have a separate namespace from the rest of the XFS_ATTR_* flags.
Give them one to make it a little more obvious that they're intent item
flags.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
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Technically speaking, objects allocated out of a specific slab cache are
supposed to be freed to that slab cache. The popular slab backends will
take care of this for us, but SLOB famously doesn't. Fix this, even if
slob + xfs are not that common of a combination.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
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When we're validating a recovered xattr log item during log recovery, we
should check the name before starting to allocate resources. This isn't
strictly necessary on its own, but it means that we won't bother with
huge memory allocations during recovery if the attr name is garbage,
which will simplify the changes in the next patch.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
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Make sure we screen the "attr flags" field of recovered xattr intent log
items to reject flag bits that we don't know about. This is really the
attr *filter* field from xfs_da_args, so rename the field and create
a mask to make checking for invalid bits easier.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
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Make sure we screen the op flags field of recovered xattr intent log
items to reject flag bits that we don't know about.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
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kmemleak reported that we lost an xfs_da_state while removing xattrs in
generic/020:
unreferenced object 0xffff88801c0e4b40 (size 480):
comm "attr", pid 30515, jiffies 4294931061 (age 5.960s)
hex dump (first 32 bytes):
78 bc 65 07 00 c9 ff ff 00 30 60 1c 80 88 ff ff x.e......0`.....
02 00 00 00 00 00 00 00 80 18 83 4e 80 88 ff ff ...........N....
backtrace:
[<ffffffffa023ef4a>] xfs_da_state_alloc+0x1a/0x30 [xfs]
[<ffffffffa021b6f3>] xfs_attr_node_hasname+0x23/0x90 [xfs]
[<ffffffffa021c6f1>] xfs_attr_set_iter+0x441/0xa30 [xfs]
[<ffffffffa02b5104>] xfs_xattri_finish_update+0x44/0x80 [xfs]
[<ffffffffa02b515e>] xfs_attr_finish_item+0x1e/0x40 [xfs]
[<ffffffffa0244744>] xfs_defer_finish_noroll+0x184/0x740 [xfs]
[<ffffffffa02a6473>] __xfs_trans_commit+0x153/0x3e0 [xfs]
[<ffffffffa021d149>] xfs_attr_set+0x469/0x7e0 [xfs]
[<ffffffffa02a78d9>] xfs_xattr_set+0x89/0xd0 [xfs]
[<ffffffff812e6512>] __vfs_removexattr+0x52/0x70
[<ffffffff812e6a08>] __vfs_removexattr_locked+0xb8/0x150
[<ffffffff812e6af6>] vfs_removexattr+0x56/0x100
[<ffffffff812e6bf8>] removexattr+0x58/0x90
[<ffffffff812e6cce>] path_removexattr+0x9e/0xc0
[<ffffffff812e6d44>] __x64_sys_lremovexattr+0x14/0x20
[<ffffffff81786b35>] do_syscall_64+0x35/0x80
I think this is a consequence of xfs_attr_node_removename_setup
attaching a new da(btree) state to xfs_attr_item and never freeing it.
I /think/ it's the case that the remove paths could detach the da state
earlier in the remove state machine since nothing else accesses the
state. However, let's future-proof the new xattr code by adding a
catch-all when we free the xfs_attr_item to make sure we never leak the
da state.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
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Because heap allocation of 64kB buffers will fail:
....
XFS: fs_mark(8414) possible memory allocation deadlock size 65768 in kmem_alloc (mode:0x2d40)
XFS: fs_mark(8417) possible memory allocation deadlock size 65768 in kmem_alloc (mode:0x2d40)
XFS: fs_mark(8409) possible memory allocation deadlock size 65768 in kmem_alloc (mode:0x2d40)
XFS: fs_mark(8428) possible memory allocation deadlock size 65768 in kmem_alloc (mode:0x2d40)
XFS: fs_mark(8430) possible memory allocation deadlock size 65768 in kmem_alloc (mode:0x2d40)
XFS: fs_mark(8437) possible memory allocation deadlock size 65768 in kmem_alloc (mode:0x2d40)
XFS: fs_mark(8433) possible memory allocation deadlock size 65768 in kmem_alloc (mode:0x2d40)
XFS: fs_mark(8406) possible memory allocation deadlock size 65768 in kmem_alloc (mode:0x2d40)
XFS: fs_mark(8412) possible memory allocation deadlock size 65768 in kmem_alloc (mode:0x2d40)
XFS: fs_mark(8432) possible memory allocation deadlock size 65768 in kmem_alloc (mode:0x2d40)
XFS: fs_mark(8424) possible memory allocation deadlock size 65768 in kmem_alloc (mode:0x2d40)
....
I'd use kvmalloc() instead, but....
- 48.19% xfs_attr_create_intent
- 46.89% xfs_attri_init
- kvmalloc_node
- 46.04% __kmalloc_node
- kmalloc_large_node
- 45.99% __alloc_pages
- 39.39% __alloc_pages_slowpath.constprop.0
- 38.89% __alloc_pages_direct_compact
- 38.71% try_to_compact_pages
- compact_zone_order
- compact_zone
- 21.09% isolate_migratepages_block
10.31% PageHuge
5.82% set_pfnblock_flags_mask
0.86% get_pfnblock_flags_mask
- 4.48% __reset_isolation_suitable
4.44% __reset_isolation_pfn
- 3.56% __pageblock_pfn_to_page
1.33% pfn_to_online_page
2.83% get_pfnblock_flags_mask
- 0.87% migrate_pages
0.86% compaction_alloc
0.84% find_suitable_fallback
- 6.60% get_page_from_freelist
4.99% clear_page_erms
- 1.19% _raw_spin_lock_irqsave
- do_raw_spin_lock
__pv_queued_spin_lock_slowpath
- 0.86% __vmalloc_node_range
0.65% __alloc_pages_bulk
.... this is just yet another reminder of how much kvmalloc() sucks.
So lift xlog_cil_kvmalloc(), rename it to xlog_kvmalloc() and use
that instead....
We also clean up the attribute name and value lengths as they no
longer need to be rounded out to sizes compatible with log vectors.
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Dave Chinner <david@fromorbit.com>
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We can't use the same algorithm for replacing an existing attribute
when logging attributes. The existing algorithm is essentially:
1. create new attr w/ INCOMPLETE
2. atomically flip INCOMPLETE flags between old + new attribute
3. remove old attr which is marked w/ INCOMPLETE
This algorithm guarantees that we see either the old or new
attribute, and if we fail after the atomic flag flip, we don't have
to recover the removal of the old attr because we never see
INCOMPLETE attributes in lookups.
For logged attributes, however, this does not work. The logged
attribute intents do not track the work that has been done as the
transaction rolls, and hence the only recovery mechanism we have is
"run the replace operation from scratch".
This is further exacerbated by the attempt to avoid needing the
INCOMPLETE flag to create an atomic swap. This means we can create
a second active attribute of the same name before we remove the
original. If we fail at any point after the create but before the
removal has completed, we end up with duplicate attributes in
the attr btree and recovery only tries to replace one of them.
There are several other failure modes where we can leave partially
allocated remote attributes that expose stale data, partially free
remote attributes that enable UAF based stale data exposure, etc.
TO fix this, we need a different algorithm for replace operations
when LARP is enabled. Luckily, it's not that complex if we take the
right first step. That is, the first thing we log is the attri
intent with the new name/value pair and mark the old attr as
INCOMPLETE in the same transaction.
From there, we then remove the old attr and keep relogging the
new name/value in the intent, such that we always know that we have
to create the new attr in recovery. Once the old attr is removed,
we then run a normal ATTR_CREATE operation relogging the intent as
we go. If the new attr is local, then it gets created in a single
atomic transaction that also logs the final intent done. If the new
attr is remote, the we set INCOMPLETE on the new attr while we
allocate and set the remote value, and then we clear the INCOMPLETE
flag at in the last transaction taht logs the final intent done.
If we fail at any point in this algorithm, log recovery will always
see the same state on disk: the new name/value in the intent, and
either an INCOMPLETE attr or no attr in the attr btree. If we find
an INCOMPLETE attr, we run the full replace starting with removing
the INCOMPLETE attr. If we don't find it, then we simply create the
new attr.
Notably, recovery of a failed create that has an INCOMPLETE flag set
is now the same - we start with the lookup of the INCOMPLETE attr,
and if that exists then we do the full replace recovery process,
otherwise we just create the new attr.
Hence changing the way we do the replace operation when LARP is
enabled allows us to use the same log recovery algorithm for both
the ATTR_CREATE and ATTR_REPLACE operations. This is also the same
algorithm we use for runtime ATTR_REPLACE operations (except for the
step setting up the initial conditions).
The result is that:
- ATTR_CREATE uses the same algorithm regardless of whether LARP is
enabled or not
- ATTR_REPLACE with larp=0 is identical to the old algorithm
- ATTR_REPLACE with larp=1 runs an unmodified attr removal algorithm
from the larp=0 code and then runs the unmodified ATTR_CREATE
code.
- log recovery when larp=1 runs the same ATTR_REPLACE algorithm as
it uses at runtime.
Because the state machine is now quite clean, changing the algorithm
is really just a case of changing the initial state and how the
states link together for the ATTR_REPLACE case. Hence it's not a
huge amount of code for what is a fairly substantial rework
of the attr logging and recovery algorithm....
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Dave Chinner <david@fromorbit.com>
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Now that xfs_attri_set_iter() has initial states for removing
attributes, switch the pure attribute removal code over to using it.
This requires attrs being removed to always be marked as INCOMPLETE
before we start the removal due to the fact we look up the attr to
remove again in xfs_attr_node_remove_attr().
Note: this drops the fillstate/refillstate optimisations from
the remove path that avoid having to look up the path again after
setting the incomplete flag and removing remote attrs. Restoring
that optimisation to this path is future Dave's problem.
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Dave Chinner <david@fromorbit.com>
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Now that the full xfs_attr_set_iter() state machine always
terminates with either the state being XFS_DAS_DONE on success or
an error on failure, we can get rid of the need for it to return
-EAGAIN whenever it needs to roll the transaction before running
the next state.
That is, we don't need to spray -EAGAIN return states everywhere,
the caller just check the state machine state for completion to
determine what action should be taken next. This greatly simplifies
the code within the state machine implementation as it now only has
to handle 0 for success or -errno for error and it doesn't need to
tell the caller to retry.
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Allison Henderson<allison.henderson@oracle.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Dave Chinner <david@fromorbit.com>
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We current use XFS_DAS_UNINIT for several steps in the attr_set
state machine. We use it for setting shortform xattrs, converting
from shortform to leaf, leaf add, leaf-to-node and leaf add. All of
these things are essentially known before we start the state machine
iterating, so we really should separate them out:
XFS_DAS_SF_ADD:
- tries to do a shortform add
- on success -> done
- on ENOSPC converts to leaf, -> XFS_DAS_LEAF_ADD
- on error, dies.
XFS_DAS_LEAF_ADD:
- tries to do leaf add
- on success:
- inline attr -> done
- remote xattr || REPLACE -> XFS_DAS_FOUND_LBLK
- on ENOSPC converts to node, -> XFS_DAS_NODE_ADD
- on error, dies
XFS_DAS_NODE_ADD:
- tries to do node add
- on success:
- inline attr -> done
- remote xattr || REPLACE -> XFS_DAS_FOUND_NBLK
- on error, dies
This makes it easier to understand how the state machine starts
up and sets us up on the path to further state machine
simplifications.
This also converts the DAS state tracepoints to use strings rather
than numbers, as converting between enums and numbers requires
manual counting rather than just reading the name.
This also introduces a XFS_DAS_DONE state so that we can trace
successful operation completions easily.
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Allison Henderson<allison.henderson@oracle.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Dave Chinner <david@fromorbit.com>
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Logged attribute intents only have set and remove types - there is
no separate intent type for a replace operation. We should have a
separate type for a replace operation, as it needs to perform
operations that neither SET or REMOVE can perform.
Add this type to the intent items and rearrange the deferred
operation setup to reflect the different operations we are
performing.
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Allison Henderson<allison.henderson@oracle.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Dave Chinner <david@fromorbit.com>
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On the first allocation of a attrd item, xfs_trans_add_item() fires
an assert like so:
XFS (pmem0): EXPERIMENTAL logged extended attributes feature added. Use at your own risk!
XFS: Assertion failed: !test_bit(XFS_LI_DIRTY, &lip->li_flags), file: fs/xfs/xfs_trans.c, line: 683
------------[ cut here ]------------
kernel BUG at fs/xfs/xfs_message.c:102!
Call Trace:
<TASK>
xfs_trans_add_item+0x17e/0x190
xfs_trans_get_attrd+0x67/0x90
xfs_attr_create_done+0x13/0x20
xfs_defer_finish_noroll+0x100/0x690
__xfs_trans_commit+0x144/0x330
xfs_trans_commit+0x10/0x20
xfs_attr_set+0x3e2/0x4c0
xfs_initxattrs+0xaa/0xe0
security_inode_init_security+0xb0/0x130
xfs_init_security+0x18/0x20
xfs_generic_create+0x13a/0x340
xfs_vn_create+0x17/0x20
path_openat+0xff3/0x12f0
do_filp_open+0xb2/0x150
The attrd log item is allocated via kmem_cache_alloc, and
xfs_log_item_init() does not zero the entire log item structure - it
assumes that the structure is already all zeros as it only
initialises non-zero fields. Fix the attr items to be allocated
via the *zalloc methods.
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Allison Henderson<allison.henderson@oracle.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Dave Chinner <david@fromorbit.com>
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Quick helper function to collapse duplicate code to initialize
transactions for attributes
Signed-off-by: Allison Henderson <allison.henderson@oracle.com>
Suggested-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Chandan Babu R <chandan.babu@oracle.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
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This is a clean up patch that merges xfs_delattr_context into
xfs_attr_item. Now that the refactoring is complete and the delayed
operation infrastructure is in place, we can combine these to eliminate
the extra struct
Signed-off-by: Allison Henderson <allison.henderson@oracle.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Chandan Babu R <chandanrlinux@gmail.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
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This patch adds an error tag that we can use to test log attribute
recovery and replay
Signed-off-by: Allison Henderson <allison.henderson@oracle.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Chandan Babu R <chandanrlinux@gmail.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
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Remove xfs_attr_set_args, xfs_attr_remove_args, and xfs_attr_trans_roll.
These high level loops are now driven by the delayed operations code,
and can be removed.
Additionally collapse in the leaf_bp parameter of xfs_attr_set_iter
since we only have one caller that passes dac->leaf_bp
Signed-off-by: Allison Henderson <allison.henderson@oracle.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Chandan Babu R <chandanrlinux@gmail.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
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This patch adds the needed routines to create, log and recover logged
extended attribute intents.
Signed-off-by: Allison Henderson <allison.henderson@oracle.com>
Reviewed-by: Chandan Babu R <chandanrlinux@gmail.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Dave Chinner <david@fromorbit.com>
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Currently attributes are modified directly across one or more
transactions. But they are not logged or replayed in the event of an
error. The goal of log attr replay is to enable logging and replaying
of attribute operations using the existing delayed operations
infrastructure. This will later enable the attributes to become part of
larger multi part operations that also must first be recorded to the
log. This is mostly of interest in the scheme of parent pointers which
would need to maintain an attribute containing parent inode information
any time an inode is moved, created, or removed. Parent pointers would
then be of interest to any feature that would need to quickly derive an
inode path from the mount point. Online scrub, nfs lookups and fs grow
or shrink operations are all features that could take advantage of this.
This patch adds two new log item types for setting or removing
attributes as deferred operations. The xfs_attri_log_item will log an
intent to set or remove an attribute. The corresponding
xfs_attrd_log_item holds a reference to the xfs_attri_log_item and is
freed once the transaction is done. Both log items use a generic
xfs_attr_log_format structure that contains the attribute name, value,
flags, inode, and an op_flag that indicates if the operations is a set
or remove.
[dchinner: added extra little bits needed for intent whiteouts]
Signed-off-by: Allison Henderson <allison.henderson@oracle.com>
Reviewed-by: Chandan Babu R <chandanrlinux@gmail.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Dave Chinner <david@fromorbit.com>
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