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Subject[PATCH v3 0/5] fs/dcache: Limit # of negative dentries
- Add a faster pruning rate when the free pool is closed to depletion.
- As suggested by James Bottomley, add an artificial delay waiting
loop before killing a negative dentry and properly clear the
DCACHE_KILL_NEGATIVE flag if killing doesn't happen.
- Add a new patch to track number of negative dentries that are
forcifully killed.

- Move the new nr_negative field to the end of dentry_stat_t structure
as suggested by Matthew Wilcox.
- With the help of Miklos Szeredi, fix incorrect locking order in
dentry_kill() by using lock_parent() instead of locking the parent's
d_lock directly.
- Correctly account for positive to negative dentry transitions.
- Automatic pruning of negative dentries will now ignore the reference
bit in negative dentries but not the regular shrinking.

A rogue application can potentially create a large number of negative
dentries in the system consuming most of the memory available. This
can impact performance of other applications running on the system.

This patchset introduces changes to the dcache subsystem to limit
the number of negative dentries allowed to be created thus limiting
the amount of memory that can be consumed by negative dentries.

Patch 1 tracks the number of negative dentries used and disallow
the creation of more when the limit is reached.

Patch 2 enables /proc/sys/fs/dentry-state to report the number of
negative dentries in the system.

Patch 3 enables automatic pruning of negative dentries when it is
close to the limit so that we won't end up killing recently used
negative dentries.

Patch 4 prevents racing between negative dentry pruning and umount

Patch 5 shows the number of forced negative dentry killings in
/proc/sys/fs/dentry-state. End users can then tune the neg_dentry_pc=
kernel boot parameter if they want to reduce forced negative dentry

Waiman Long (5):
fs/dcache: Limit numbers of negative dentries
fs/dcache: Report negative dentry number in dentry-state
fs/dcache: Enable automatic pruning of negative dentries
fs/dcache: Protect negative dentry pruning from racing with umount
fs/dcache: Track count of negative dentries forcibly killed

Documentation/admin-guide/kernel-parameters.txt | 7 +
fs/dcache.c | 451 ++++++++++++++++++++++--
include/linux/dcache.h | 8 +-
include/linux/list_lru.h | 1 +
mm/list_lru.c | 4 +-
5 files changed, 435 insertions(+), 36 deletions(-)


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