- Jan 08, 2011
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Joe Perches authored
Signed-off-by:
Joe Perches <joe@perches.com> Signed-off-by:
Matthew Garrett <mjg@redhat.com>
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Sreedhara DS authored
This driver implements ioctl and interfaces with intel scu ipc driver. It is used to access pmic/msic registers from user space and firmware update utility. Signed-off-by:
Sreedhara DS <sreedhara.ds@intel.com> [Extensive clean up and debug] Signed-off-by:
Alan Cox <alan@linux.intel.com> Signed-off-by:
Matthew Garrett <mjg@redhat.com>
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git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb-2.6Linus Torvalds authored
* 'usb-next' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb-2.6: (144 commits) USB: add support for Dream Cheeky DL100B Webmail Notifier (1d34:0004) USB: serial: ftdi_sio: add support for TIOCSERGETLSR USB: ehci-mxc: Setup portsc register prior to accessing OTG viewport USB: atmel_usba_udc: fix freeing irq in usba_udc_remove() usb: ehci-omap: fix tll channel enable mask usb: ohci-omap3: fix trivial typo USB: gadget: ci13xxx: don't assume that PAGE_SIZE is 4096 USB: gadget: ci13xxx: fix complete() callback for no_interrupt rq's USB: gadget: update ci13xxx to work with g_ether USB: gadgets: ci13xxx: fix probing of compiled-in gadget drivers Revert "USB: musb: pm: don't rely fully on clock support" Revert "USB: musb: blackfin: pm: make it work" USB: uas: Use GFP_NOIO instead of GFP_KERNEL in I/O submission path USB: uas: Ensure we only bind to a UAS interface USB: uas: Rename sense pipe and sense urb to status pipe and status urb USB: uas: Use kzalloc instead of kmalloc USB: uas: Fix up the Sense IU usb: musb: core: kill unneeded #include's DA8xx: assign name to MUSB IRQ resource usb: gadget: g_ncm added ... Manually fix up trivial conflicts in USB Kconfig changes in: arch/arm/mach-omap2/Kconfig arch/sh/Kconfig drivers/usb/Kconfig drivers/usb/host/ehci-hcd.c and annoying chip clock data conflicts in: arch/arm/mach-omap2/clock3xxx_data.c arch/arm/mach-omap2/clock44xx_data.c
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git://git.kernel.org/pub/scm/linux/kernel/git/jejb/scsi-misc-2.6Linus Torvalds authored
* git://git.kernel.org/pub/scm/linux/kernel/git/jejb/scsi-misc-2.6: (147 commits) [SCSI] arcmsr: fix write to device check [SCSI] lpfc: lower stack use in lpfc_fc_frame_check [SCSI] eliminate an unnecessary local variable from scsi_remove_target() [SCSI] libiscsi: use bh locking instead of irq with session lock [SCSI] libiscsi: do not take host lock in queuecommand [SCSI] be2iscsi: fix null ptr when accessing task hdr [SCSI] be2iscsi: fix gfp use in alloc_pdu [SCSI] libiscsi: add more informative failure message during iscsi scsi eh [SCSI] gdth: Add missing call to gdth_ioctl_free [SCSI] bfa: remove unused defintions and misc cleanups [SCSI] bfa: remove inactive functions [SCSI] bfa: replace bfa_assert with WARN_ON [SCSI] qla2xxx: Use sg_next to fetch next sg element while walking sg list. [SCSI] qla2xxx: Fix to avoid recursive lock failure during BSG timeout. [SCSI] qla2xxx: Remove code to not reset ISP82xx on failure. [SCSI] qla2xxx: Display mailbox register 4 during 8012 AEN for ISP82XX parts. [SCSI] qla2xxx: Don't perform a BIG_HAMMER if Get-ID (0x20) mailbox command fails on CNAs. [SCSI] qla2xxx: Remove redundant module parameter permission bits [SCSI] qla2xxx: Add sysfs node for displaying board temperature. [SCSI] qla2xxx: Code cleanup to remove unwanted comments and code. ...
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Dan Carpenter authored
There was a semi-colon missing and it broke the compile. Signed-off-by:
Dan Carpenter <error27@gmail.com> Cc: Dmitry Torokhov <dmitry.torokhov@gmail.com> Signed-off-by:
Linus Walleij <linus.walleij@stericsson.com> Signed-off-by:
Linus Torvalds <torvalds@linux-foundation.org>
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Linus Torvalds authored
Merge branch 'vfs-scale-working' of git://git.kernel.org/pub/scm/linux/kernel/git/npiggin/linux-npiggin * 'vfs-scale-working' of git://git.kernel.org/pub/scm/linux/kernel/git/npiggin/linux-npiggin: (57 commits) fs: scale mntget/mntput fs: rename vfsmount counter helpers fs: implement faster dentry memcmp fs: prefetch inode data in dcache lookup fs: improve scalability of pseudo filesystems fs: dcache per-inode inode alias locking fs: dcache per-bucket dcache hash locking bit_spinlock: add required includes kernel: add bl_list xfs: provide simple rcu-walk ACL implementation btrfs: provide simple rcu-walk ACL implementation ext2,3,4: provide simple rcu-walk ACL implementation fs: provide simple rcu-walk generic_check_acl implementation fs: provide rcu-walk aware permission i_ops fs: rcu-walk aware d_revalidate method fs: cache optimise dentry and inode for rcu-walk fs: dcache reduce branches in lookup path fs: dcache remove d_mounted fs: fs_struct use seqlock fs: rcu-...
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- Jan 07, 2011
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Nick Piggin authored
The problem that this patch aims to fix is vfsmount refcounting scalability. We need to take a reference on the vfsmount for every successful path lookup, which often go to the same mount point. The fundamental difficulty is that a "simple" reference count can never be made scalable, because any time a reference is dropped, we must check whether that was the last reference. To do that requires communication with all other CPUs that may have taken a reference count. We can make refcounts more scalable in a couple of ways, involving keeping distributed counters, and checking for the global-zero condition less frequently. - check the global sum once every interval (this will delay zero detection for some interval, so it's probably a showstopper for vfsmounts). - keep a local count and only taking the global sum when local reaches 0 (this is difficult for vfsmounts, because we can't hold preempt off for the life of a reference, so a counter would need to be per-thread or tied strongly to a particular CPU which requires more locking). - keep a local difference of increments and decrements, which allows us to sum the total difference and hence find the refcount when summing all CPUs. Then, keep a single integer "long" refcount for slow and long lasting references, and only take the global sum of local counters when the long refcount is 0. This last scheme is what I implemented here. Attached mounts and process root and working directory references are "long" references, and everything else is a short reference. This allows scalable vfsmount references during path walking over mounted subtrees and unattached (lazy umounted) mounts with processes still running in them. This results in one fewer atomic op in the fastpath: mntget is now just a per-CPU inc, rather than an atomic inc; and mntput just requires a spinlock and non-atomic decrement in the common case. However code is otherwise bigger and heavier, so single threaded performance is basically a wash. Signed-off-by:
Nick Piggin <npiggin@kernel.dk>
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Nick Piggin authored
Suggested by Andreas, mnt_ prefix is clearer namespace, follows kernel conventions better, and is easier for tab complete. I introduced these names so I'll admit they were not good choices. Signed-off-by:
Nick Piggin <npiggin@kernel.dk>
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Nick Piggin authored
The standard memcmp function on a Westmere system shows up hot in profiles in the `git diff` workload (both parallel and single threaded), and it is likely due to the costs associated with trapping into microcode, and little opportunity to improve memory access (dentry name is not likely to take up more than a cacheline). So replace it with an open-coded byte comparison. This increases code size by 8 bytes in the critical __d_lookup_rcu function, but the speedup is huge, averaging 10 runs of each: git diff st user sys elapsed CPU before 1.15 2.57 3.82 97.1 after 1.14 2.35 3.61 96.8 git diff mt user sys elapsed CPU before 1.27 3.85 1.46 349 after 1.26 3.54 1.43 333 Elapsed time for single threaded git diff at 95.0% confidence: -0.21 +/- 0.01 -5.45% +/- 0.24% It's -0.66% +/- 0.06% elapsed time on my Opteron, so rep cmp costs on the fam10h seem to be relatively smaller, but there is still a win. Signed-off-by:
Nick Piggin <npiggin@kernel.dk>
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Nick Piggin authored
This makes single threaded git diff -1.25% +/- 0.05% elapsed time on my 2s12c24t Westmere system, and -0.86% +/- 0.05% on my 2s8c Barcelona, by prefetching the important first cacheline of the inode in while we do the actual name compare and other operations on the dentry. There was no measurable slowdown in the single file stat case, or the creat case (where negative dentries would be common). Signed-off-by:
Nick Piggin <npiggin@kernel.dk>
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Nick Piggin authored
Regardless of how much we possibly try to scale dcache, there is likely always going to be some fundamental contention when adding or removing children under the same parent. Pseudo filesystems do not seem need to have connected dentries because by definition they are disconnected. Signed-off-by:
Nick Piggin <npiggin@kernel.dk>
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Nick Piggin authored
dcache_inode_lock can be replaced with per-inode locking. Use existing inode->i_lock for this. This is slightly non-trivial because we sometimes need to find the inode from the dentry, which requires d_inode to be stabilised (either with refcount or d_lock). Signed-off-by:
Nick Piggin <npiggin@kernel.dk>
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Nick Piggin authored
We can turn the dcache hash locking from a global dcache_hash_lock into per-bucket locking. Signed-off-by:
Nick Piggin <npiggin@kernel.dk>
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Nick Piggin authored
Signed-off-by:
Nick Piggin <npiggin@kernel.dk>
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Nick Piggin authored
Introduce a type of hlist that can support the use of the lowest bit in the hlist_head. This will be subsequently used to implement per-bucket bit spinlock for inode and dentry hashes, and may be useful in other cases such as network hashes. Reviewed-by:
Paul E. McKenney <paulmck@linux.vnet.ibm.com> Signed-off-by:
Nick Piggin <npiggin@kernel.dk>
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Nick Piggin authored
This simple implementation just checks for no ACLs on the inode, and if so, then the rcu-walk may proceed, otherwise fail it. Signed-off-by:
Nick Piggin <npiggin@kernel.dk>
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Nick Piggin authored
This simple implementation just checks for no ACLs on the inode, and if so, then the rcu-walk may proceed, otherwise fail it. Signed-off-by:
Nick Piggin <npiggin@kernel.dk>
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Nick Piggin authored
This simple implementation just checks for no ACLs on the inode, and if so, then the rcu-walk may proceed, otherwise fail it. Signed-off-by:
Nick Piggin <npiggin@kernel.dk>
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Nick Piggin authored
This simple implementation just checks for no ACLs on the inode, and if so, then the rcu-walk may proceed, otherwise fail it. This could easily be extended to put acls under RCU and check them under seqlock, if need be. But this implementation is enough to show the rcu-walk aware permissions code for path lookups is working, and will handle cases where there are no ACLs or ACLs in just the final element. This patch implicity converts tmpfs to rcu-aware permission check. Subsequent patches onvert ext*, xfs, and, btrfs. Each of these uses acl/permission code in a different way, so convert them all to provide templates and proof of concept. Signed-off-by:
Nick Piggin <npiggin@kernel.dk>
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Nick Piggin authored
Signed-off-by:
Nick Piggin <npiggin@kernel.dk>
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Nick Piggin authored
Require filesystems be aware of .d_revalidate being called in rcu-walk mode (nd->flags & LOOKUP_RCU). For now do a simple push down, returning -ECHILD from all implementations. Signed-off-by:
Nick Piggin <npiggin@kernel.dk>
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Nick Piggin authored
Put dentry and inode fields into top of data structure. This allows RCU path traversal to perform an RCU dentry lookup in a path walk by touching only the first 56 bytes of the dentry. We also fit in 8 bytes of inline name in the first 64 bytes, so for short names, only 64 bytes needs to be touched to perform the lookup. We should get rid of the hash->prev pointer from the first 64 bytes, and fit 16 bytes of name in there, which will take care of 81% rather than 32% of the kernel tree. inode is also rearranged so that RCU lookup will only touch a single cacheline in the inode, plus one in the i_ops structure. This is important for directory component lookups in RCU path walking. In the kernel source, directory names average is around 6 chars, so this works. When we reach the last element of the lookup, we need to lock it and take its refcount which requires another cacheline access. Align dentry and inode operations structs, so members will be at predictable offsets and we can group common operations into head of structure. Signed-off-by:
Nick Piggin <npiggin@kernel.dk>
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Nick Piggin authored
Reduce some branches and memory accesses in dcache lookup by adding dentry flags to indicate common d_ops are set, rather than having to check them. This saves a pointer memory access (dentry->d_op) in common path lookup situations, and saves another pointer load and branch in cases where we have d_op but not the particular operation. Patched with: git grep -E '[.>]([[:space:]])*d_op([[:space:]])*=' | xargs sed -e 's/\([^\t ]*\)->d_op = \(.*\);/d_set_d_op(\1, \2);/' -e 's/\([^\t ]*\)\.d_op = \(.*\);/d_set_d_op(\&\1, \2);/' -i Signed-off-by:
Nick Piggin <npiggin@kernel.dk>
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Nick Piggin authored
Rather than keep a d_mounted count in the dentry, set a dentry flag instead. The flag can be cleared by checking the hash table to see if there are any mounts left, which is not time critical because it is performed at detach time. The mounted state of a dentry is only used to speculatively take a look in the mount hash table if it is set -- before following the mount, vfsmount lock is taken and mount re-checked without races. This saves 4 bytes on 32-bit, nothing on 64-bit but it does provide a hole I might use later (and some configs have larger than 32-bit spinlocks which might make use of the hole). Autofs4 conversion and changelog by Ian Kent <raven@themaw.net>: In autofs4, when expring direct (or offset) mounts we need to ensure that we block user path walks into the autofs mount, which is covered by another mount. To do this we clear the mounted status so that follows stop before walking into the mount and are essentially blocked until the expire is completed. The automount daemon still finds the correct dentry for the umount due to the follow mount logic in fs/autofs4/root.c:autofs4_follow_link(), which is set as an inode operation for direct and offset mounts only and is called following the lookup that stopped at the covered mount. At the end of the expire the covering mount probably has gone away so the mounted status need not be restored. But we need to check this and only restore the mounted status if the expire failed. XXX: autofs may not work right if we have other mounts go over the top of it? Signed-off-by:
Nick Piggin <npiggin@kernel.dk>
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Nick Piggin authored
Use a seqlock in the fs_struct to enable us to take an atomic copy of the complete cwd and root paths. Use this in the RCU lookup path to avoid a thread-shared spinlock in RCU lookup operations. Multi-threaded apps may now perform path lookups with scalability matching multi-process apps. Operations such as stat(2) become very scalable for multi-threaded workload. Signed-off-by:
Nick Piggin <npiggin@kernel.dk>
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Nick Piggin authored
Perform common cases of path lookups without any stores or locking in the ancestor dentry elements. This is called rcu-walk, as opposed to the current algorithm which is a refcount based walk, or ref-walk. This results in far fewer atomic operations on every path element, significantly improving path lookup performance. It also avoids cacheline bouncing on common dentries, significantly improving scalability. The overall design is like this: * LOOKUP_RCU is set in nd->flags, which distinguishes rcu-walk from ref-walk. * Take the RCU lock for the entire path walk, starting with the acquiring of the starting path (eg. root/cwd/fd-path). So now dentry refcounts are not required for dentry persistence. * synchronize_rcu is called when unregistering a filesystem, so we can access d_ops and i_ops during rcu-walk. * Similarly take the vfsmount lock for the entire path walk. So now mnt refcounts are not required for persistence. Also we are free to perform mount lookups, and to assume dentry mount points and mount roots are stable up and down the path. * Have a per-dentry seqlock to protect the dentry name, parent, and inode, so we can load this tuple atomically, and also check whether any of its members have changed. * Dentry lookups (based on parent, candidate string tuple) recheck the parent sequence after the child is found in case anything changed in the parent during the path walk. * inode is also RCU protected so we can load d_inode and use the inode for limited things. * i_mode, i_uid, i_gid can be tested for exec permissions during path walk. * i_op can be loaded. When we reach the destination dentry, we lock it, recheck lookup sequence, and increment its refcount and mountpoint refcount. RCU and vfsmount locks are dropped. This is termed "dropping rcu-walk". If the dentry refcount does not match, we can not drop rcu-walk gracefully at the current point in the lokup, so instead return -ECHILD (for want of a better errno). This signals the path walking code to re-do the entire lookup with a ref-walk. Aside from the final dentry, there are other situations that may be encounted where we cannot continue rcu-walk. In that case, we drop rcu-walk (ie. take a reference on the last good dentry) and continue with a ref-walk. Again, if we can drop rcu-walk gracefully, we return -ECHILD and do the whole lookup using ref-walk. But it is very important that we can continue with ref-walk for most cases, particularly to avoid the overhead of double lookups, and to gain the scalability advantages on common path elements (like cwd and root). The cases where rcu-walk cannot continue are: * NULL dentry (ie. any uncached path element) * parent with d_inode->i_op->permission or ACLs * dentries with d_revalidate * Following links In future patches, permission checks and d_revalidate become rcu-walk aware. It may be possible eventually to make following links rcu-walk aware. Uncached path elements will always require dropping to ref-walk mode, at the very least because i_mutex needs to be grabbed, and objects allocated. Signed-off-by:
Nick Piggin <npiggin@kernel.dk>
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Nick Piggin authored
Add branch annotations for seqlock read fastpath, and introduce __read_seqcount_begin and __read_seqcount_end functions, that can avoid the smp_rmb() if used carefully. These will be used by store-free path walking algorithm performance is critical and seqlocks are in use. Signed-off-by:
Nick Piggin <npiggin@kernel.dk>
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Nick Piggin authored
Pseudo filesystems that don't put inode on RCU list or reachable by rcu-walk dentries do not need to RCU free their inodes. Signed-off-by:
Nick Piggin <npiggin@kernel.dk>
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Nick Piggin authored
RCU free the struct inode. This will allow: - Subsequent store-free path walking patch. The inode must be consulted for permissions when walking, so an RCU inode reference is a must. - sb_inode_list_lock to be moved inside i_lock because sb list walkers who want to take i_lock no longer need to take sb_inode_list_lock to walk the list in the first place. This will simplify and optimize locking. - Could remove some nested trylock loops in dcache code - Could potentially simplify things a bit in VM land. Do not need to take the page lock to follow page->mapping. The downsides of this is the performance cost of using RCU. In a simple creat/unlink microbenchmark, performance drops by about 10% due to inability to reuse cache-hot slab objects. As iterations increase and RCU freeing starts kicking over, this increases to about 20%. In cases where inode lifetimes are longer (ie. many inodes may be allocated during the average life span of a single inode), a lot of this cache reuse is not applicable, so the regression caused by this patch is smaller. The cache-hot regression could largely be avoided by using SLAB_DESTROY_BY_RCU, however this adds some complexity to list walking and store-free path walking, so I prefer to implement this at a later date, if it is shown to be a win in real situations. I haven't found a regression in any non-micro benchmark so I doubt it will be a problem. Signed-off-by:
Nick Piggin <npiggin@kernel.dk>
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Nick Piggin authored
The tricky locking for disposing of a dentry is duplicated 3 times in the dcache (dput, pruning a dentry from the LRU, and pruning its ancestors). Consolidate them all into a single function dentry_kill. Signed-off-by:
Nick Piggin <npiggin@kernel.dk>
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Nick Piggin authored
Signed-off-by:
Nick Piggin <npiggin@kernel.dk>
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Nick Piggin authored
Signed-off-by:
Nick Piggin <npiggin@kernel.dk>
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Nick Piggin authored
prune_one_dentry can avoid quite a bit of locking in the common case where ancestors have an elevated refcount. Alternatively, we could have gone the other way and made fewer trylocks in the case where d_count goes to zero, but is probably less common. Signed-off-by:
Nick Piggin <npiggin@kernel.dk>
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Nick Piggin authored
Use RCU to simplify locking in dget_parent. Signed-off-by:
Nick Piggin <npiggin@kernel.dk>
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Nick Piggin authored
dget_locked was a shortcut to avoid the lazy lru manipulation when we already held dcache_lock (lru manipulation was relatively cheap at that point). However, how that the lru lock is an innermost one, we never hold it at any caller, so the lock cost can now be avoided. We already have well working lazy dcache LRU, so it should be fine to defer LRU manipulations to scan time. Signed-off-by:
Nick Piggin <npiggin@kernel.dk>
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Nick Piggin authored
dcache_inode_lock can be avoided in d_delete() and d_materialise_unique() in cases where it is not required. Signed-off-by:
Nick Piggin <npiggin@kernel.dk>
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Nick Piggin authored
Signed-off-by:
Nick Piggin <npiggin@kernel.dk>
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Nick Piggin authored
It is possible to run dput without taking data structure locks up-front. In many cases where we don't kill the dentry anyway, these locks are not required. Signed-off-by:
Nick Piggin <npiggin@kernel.dk>
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Nick Piggin authored
Long lived dcache "multi-step" operations which retry on rename seq can be starved with a lot of rename activity. If they fail after the 1st pass, take the rename_lock for writing to avoid further starvation. Signed-off-by:
Nick Piggin <npiggin@kernel.dk>
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Nick Piggin authored
dcache_lock no longer protects anything. remove it. Signed-off-by:
Nick Piggin <npiggin@kernel.dk>
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