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Personal/nitinsingla/few fixes #165

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Nagendra Tomar added 30 commits October 13, 2024 11:40
… directory cache purge of the current directory inode
…e not changed.

w/o this read only scenarios, we can have attr expire and then get_file_size() will
return -1 and we will not do readahead.
…of whether it could or could not add the entry to directory cache.

This is because if a file/dir is created inside a directory, our cache technically
becomes out of sync with the server. Note that w emay fail to add to the directory
cache because it may be full or some other error.
…) and send_readdir_or_readdirplus_response() to fix an inode leak

Now we hold inode lookupcnt ref for all entries with a valid inode.
This way, send_readdir_or_readdirplus_response() can call decref() for the inodes
it doens't pass to fuse. Previously we were decrementing dircachecnt and there was a possibility
of that becoming 0 while lookupcnt was already 0. Those inodes would be sitting in inode_map
with lookupcnt=dircachecnt=0.
We rename all locks to the form <context>_lock_N. N is the order of the
lock. A thread can only hold a higher order lock (greater N) then the highest
order lock it's currently holding, i.e., a thread holding a lock *_lock_N
cannot hold any lock from *_lock_0 to *_lock_N-1 (it can only hold *_lock_N+1
and higher order locks).
Later I plan to add assertions to catch violations of the above rule.

nfs_client::inode_map_lock -> nfs_client::inode_map_lock_0
nfs_inode::ilock -> nfs_inode::ilock_1
nfs_inode::readdircache_lock -> nfs_inode::readdircache_lock_2
nfs_client::jukebox_seeds_lock -> nfs_client::jukebox_seeds_lock_39
ra_state::ra_lock -> ra_state::ra_lock_40
rpc_task_helper::task_index_lock -> rpc_task_helper::task_index_lock_41
rpc_stats_az::stats_lock -> rpc_stats_az::stats_lock_42
bytes_chunk_cache::chunkmap_lock -> bytes_chunk_cache::chunkmap_lock_43
membuf::mb_lock -> membuf::mb_lock_44
…correctly

as we were clearing the nfs_inode.
Added a TODO to fix it.
Also fixed a log for readdir.
Applications don't seem to handle it well.
… place

Made directory_entry purely readonly so that we don't update it, as
users of that are not expecting it to change. So, if we receive a
LOOKUP response for a Type (2)  entry which is present, we remove that
entry and create a new one.
After that, hold inode lock if we have to update the inode.
Fix rastate.
Nagendra Tomar and others added 27 commits January 27, 2025 05:41
…side sync_membufs() is senn to fail sometimes.
…side sync_membufs() is senn to fail sometimes.
… before starting the first write in sync_membufs()
Co-authored-by: Ubuntu <shubham@shubham808VM-westeurope.2vwp434kux0ehoz4y3jbj5wcwa.ax.internal.cloudapp.net>
This can be called when cache is being shutdown on file close.
This will delete dirty/uncommitted membufs too.
Co-authored-by: Nagendra Tomar <[email protected]>
…e flush to complete.

We cannot hold flush_lock while waiting for any WRITE RPCs to complete as
write_iov_callback()->on_flush_complete() also grabs the flush_lock.
This can cause a deadlock.
…the flush to complete

We have a rule that anyone waiting for a write to complete must not
hold the flush_lock as the write_iov_callback() also may hold the flush
lock.
else we can have a deadlock where write_iov_callback() first releases
the membuf lock which make wait_for_ongoing_flush() believe that all
flush are done and it can take the flush_lock safely, but write_iov_callback()
calls on_flush_complete() later which grabs the flush_lock. This can
cause a deadlock. The fix is to let the callback drain. Since
wait_for_ongoing_flush() is a rarely used function, we make that
check while write_iov_callback() can run w/o any additional check or
complexity.
Another way of solving this would be to release the membuf lock
after on_flush_complete() runs, but then it would have added unncessary
restrictions on what we can do insode on_flush_complete().

Co-authored-by: Nagendra Tomar <[email protected]>
Some of the fcsm asserts were incorrectly disabled, enabled them.
Also added assert that we always write full bcs to the backend, else we have
issues as dirty/flushing/committed flags are tracked at membuf granularity.

Co-authored-by: Nagendra Tomar <[email protected]>
* Implement 2 phase truncate.

This change gets rid of SCAN_ACTION_TRUNCATE and removes truncate
support from bytes_chunk_cache::scan(). Now scan() cannot remove
membufs which are in use or dirty. truncate() is a separate function
now which specializes in truncating the cache and duly waits for
locked bcs. It assumes that truncate will be called from contexts
which can afford to wait and correctness is more important.

* Enforce mb is locked and inuse inside trim().

* Undo the req to have membuf locked and inuse inside trim()

It's hard to guarantee that, especially from ~bc_iovec().

* Increase max_retry to 200

to properly handle cases where we induce sleep in the write callback

* Do not flush truncated membufs.

---------

Co-authored-by: Nagendra Tomar <[email protected]>
* file_cache.* initial

* Audit of Nitin's unstable write PR

Audited file_cache.h
Audited file_cache.cpp

---------

Co-authored-by: Nagendra Tomar <[email protected]>
fcsm.h
fcsm.cpp
nfs_inode.h
rpc_stats.cpp
fcsm.h
fcsm.cpp

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@nitin-deamon nitin-deamon force-pushed the personal/nitinsingla/few-fixes branch from 0be2f2d to 76f82d3 Compare February 10, 2025 16:33
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6 participants