linux.git/fs/cachefiles/daemon.c, branch v6.8

cachefiles: fix memory leak in cachefiles_add_cache()

2024-02-20T08:46:07+00:00

The following memory leak was reported after unbinding /dev/cachefiles:

==================================================================
unreferenced object 0xffff9b674176e3c0 (size 192):
  comm "cachefilesd2", pid 680, jiffies 4294881224
  hex dump (first 32 bytes):
    01 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
  backtrace (crc ea38a44b):
    [] kmem_cache_alloc+0x2d5/0x370
    [] prepare_creds+0x26/0x2e0
    [] cachefiles_determine_cache_security+0x1f/0x120
    [] cachefiles_add_cache+0x13c/0x3a0
    [] cachefiles_daemon_write+0x146/0x1c0
    [] vfs_write+0xcb/0x520
    [] ksys_write+0x69/0xf0
    [] do_syscall_64+0x72/0x140
    [] entry_SYSCALL_64_after_hwframe+0x6e/0x76
==================================================================

Put the reference count of cache_cred in cachefiles_daemon_unbind() to
fix the problem. And also put cache_cred in cachefiles_add_cache() error
branch to avoid memory leaks.

Fixes: 9ae326a69004 ("CacheFiles: A cache that backs onto a mounted filesystem")
CC: stable@vger.kernel.org
Signed-off-by: Baokun Li 
Link: https://lore.kernel.org/r/20240217081431.796809-1-libaokun1@huawei.com
Acked-by: David Howells 
Reviewed-by: Jingbo Xu 
Reviewed-by: Jeff Layton 
Signed-off-by: Christian Brauner

cachefiles: add restore command to recover inflight ondemand read requests

2023-11-25T15:03:57+00:00

Previously, in ondemand read scenario, if the anonymous fd was closed by
user daemon, inflight and subsequent read requests would return EIO.
As long as the device connection is not released, user daemon can hold
and restore inflight requests by setting the request flag to
CACHEFILES_REQ_NEW.

Suggested-by: Gao Xiang 
Signed-off-by: Jia Zhu 
Signed-off-by: Xin Yin 
Link: https://lore.kernel.org/r/20231120041422.75170-6-zhujia.zj@bytedance.com
Reviewed-by: Jingbo Xu 
Reviewed-by: David Howells 
Signed-off-by: Christian Brauner

cachefiles: narrow the scope of triggering EPOLLIN events in ondemand mode

2023-11-25T15:03:57+00:00

Don't trigger EPOLLIN when there are only reopening read requests in
xarray.

Suggested-by: Xin Yin 
Signed-off-by: Jia Zhu 
Link: https://lore.kernel.org/r/20231120041422.75170-5-zhujia.zj@bytedance.com
Reviewed-by: Jingbo Xu 
Reviewed-by: David Howells 
Signed-off-by: Christian Brauner

cachefiles: enable on-demand read mode

2022-05-17T16:11:18+00:00

Enable on-demand read mode by adding an optional parameter to the "bind"
command.

On-demand mode will be turned on when this parameter is "ondemand", i.e.
"bind ondemand". Otherwise cachefiles will work in the original mode.

Signed-off-by: Jeffle Xu 
Link: https://lore.kernel.org/r/20220509074028.74954-7-jefflexu@linux.alibaba.com
Acked-by: David Howells 
Signed-off-by: Gao Xiang

cachefiles: unbind cachefiles gracefully in on-demand mode

2022-05-17T16:11:17+00:00

Add a refcount to avoid the deadlock in on-demand read mode. The
on-demand read mode will pin the corresponding cachefiles object for
each anonymous fd. The cachefiles object is unpinned when the anonymous
fd gets closed. When the user daemon exits and the fd of
"/dev/cachefiles" device node gets closed, it will wait for all
cahcefiles objects getting withdrawn. Then if there's any anonymous fd
getting closed after the fd of the device node, the user daemon will
hang forever, waiting for all objects getting withdrawn.

To fix this, add a refcount indicating if there's any object pinned by
anonymous fds. The cachefiles cache gets unbound and withdrawn when the
refcount is decreased to 0. It won't change the behaviour of the
original mode, in which case the cachefiles cache gets unbound and
withdrawn as long as the fd of the device node gets closed.

Signed-off-by: Jeffle Xu 
Link: https://lore.kernel.org/r/20220509074028.74954-4-jefflexu@linux.alibaba.com
Acked-by: David Howells 
Signed-off-by: Gao Xiang

cachefiles: notify the user daemon when looking up cookie

2022-05-17T16:11:17+00:00

Fscache/CacheFiles used to serve as a local cache for a remote
networking fs. A new on-demand read mode will be introduced for
CacheFiles, which can boost the scenario where on-demand read semantics
are needed, e.g. container image distribution.

The essential difference between these two modes is seen when a cache
miss occurs: In the original mode, the netfs will fetch the data from
the remote server and then write it to the cache file; in on-demand
read mode, fetching the data and writing it into the cache is delegated
to a user daemon.

As the first step, notify the user daemon when looking up cookie. In
this case, an anonymous fd is sent to the user daemon, through which the
user daemon can write the fetched data to the cache file. Since the user
daemon may move the anonymous fd around, e.g. through dup(), an object
ID uniquely identifying the cache file is also attached.

Also add one advisory flag (FSCACHE_ADV_WANT_CACHE_SIZE) suggesting that
the cache file size shall be retrieved at runtime. This helps the
scenario where one cache file contains multiple netfs files, e.g. for
the purpose of deduplication. In this case, netfs itself has no idea the
size of the cache file, whilst the user daemon should give the hint on
it.

Signed-off-by: Jeffle Xu 
Link: https://lore.kernel.org/r/20220509074028.74954-3-jefflexu@linux.alibaba.com
Acked-by: David Howells 
Signed-off-by: Gao Xiang

cachefiles: set default tag name if it's unspecified

2022-01-21T21:36:28+00:00

fscache_acquire_cache() requires a non-empty name, while 'tag '
command is optional for cachefilesd.

Thus set default tag name if it's unspecified to avoid the regression of
cachefilesd. The logic is the same with that before rewritten.

Signed-off-by: Jeffle Xu 
Signed-off-by: David Howells 
Reviewed-by: Jeff Layton 
cc: linux-cachefs@redhat.com
Link: https://lore.kernel.org/r/164251399914.3435901.4761991152407411408.stgit@warthog.procyon.org.uk/ # v1

fscache, cachefiles: Display stats of no-space events

2022-01-07T13:43:13+00:00

Add stat counters of no-space events that caused caching not to happen and
display in /proc/fs/fscache/stats.

Signed-off-by: David Howells 
Reviewed-by: Jeff Layton 
cc: linux-cachefs@redhat.com
Link: https://lore.kernel.org/r/163819653216.215744.17210522251617386509.stgit@warthog.procyon.org.uk/ # v1
Link: https://lore.kernel.org/r/163906958369.143852.7257100711818401748.stgit@warthog.procyon.org.uk/ # v2
Link: https://lore.kernel.org/r/163967166917.1823006.14842444049198947892.stgit@warthog.procyon.org.uk/ # v3
Link: https://lore.kernel.org/r/164021566184.640689.4417328329632709265.stgit@warthog.procyon.org.uk/ # v4

cachefiles: Allow cachefiles to actually function

2022-01-07T13:43:07+00:00

Remove the block that allowed cachefiles to be compiled but prevented it
from actually starting a cache.

Signed-off-by: David Howells 
Reviewed-by: Jeff Layton 
cc: linux-cachefs@redhat.com
Link: https://lore.kernel.org/r/163819649497.215744.2872504990762846767.stgit@warthog.procyon.org.uk/ # v1
Link: https://lore.kernel.org/r/163906956491.143852.4951522864793559189.stgit@warthog.procyon.org.uk/ # v2
Link: https://lore.kernel.org/r/163967165374.1823006.14248189932202373809.stgit@warthog.procyon.org.uk/ # v3
Link: https://lore.kernel.org/r/164021564379.640689.7921380491176827442.stgit@warthog.procyon.org.uk/ # v4

cachefiles: Implement backing file wrangling

2022-01-07T13:42:40+00:00

Implement the wrangling of backing files, including the following pieces:

(1) Lookup and creation of a file on disk, using a tmpfile if the file
isn't yet present. The file is then opened, sized for DIO and the
file handle is attached to the cachefiles_object struct. The inode is
marked to indicate that it's in use by a kernel service.

(2) Invalidation of an object, creating a tmpfile and switching the file
pointer in the cachefiles object.

(3) Committing a file to disk, including setting the coherency xattr on it
and, if necessary, creating a hard link to it.

Note that this would be a good place to use Omar Sandoval's vfs_link()
with AT_LINK_REPLACE[1] as I may have to unlink an old file before I
can link a tmpfile into place.

(4) Withdrawal of open objects when a cache is being withdrawn or a cookie
is relinquished. This involves committing or discarding the file.

Changes
=======
ver #2:
- Fix logging of wrong error[1].

Signed-off-by: David Howells
Reviewed-by: Jeff Layton
cc: linux-cachefs@redhat.com
Link: https://lore.kernel.org/r/20211203094950.GA2480@kili/ [1]
Link: https://lore.kernel.org/r/163819644097.215744.4505389616742411239.stgit@warthog.procyon.org.uk/ # v1
Link: https://lore.kernel.org/r/163906949512.143852.14222856795032602080.stgit@warthog.procyon.org.uk/ # v2
Link: https://lore.kernel.org/r/163967158526.1823006.17482695321424642675.stgit@warthog.procyon.org.uk/ # v3
Link: https://lore.kernel.org/r/164021557060.640689.16373541458119269871.stgit@warthog.procyon.org.uk/ # v4