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authorDavid Howells <dhowells@redhat.com>2021-10-20 17:26:17 +0300
committerDavid Howells <dhowells@redhat.com>2022-01-07 12:22:19 +0300
commit62ab63352350e881ae693a8236b35d7d0516c78b (patch)
treee8174b7e40b702f6737ea5e42c44793d0d552fad /fs/fscache/Makefile
parent9549332df4ed4e761a1d41c83f2c25d28bb22431 (diff)
downloadlinux-62ab63352350e881ae693a8236b35d7d0516c78b.tar.xz
fscache: Implement volume registration
Add functions to the fscache API to allow volumes to be acquired and relinquished by the network filesystem. A volume is an index of data storage cache objects. A volume is represented by a volume cookie in the API. A filesystem would typically create a volume for a superblock and then create per-inode cookies within it. To request a volume, the filesystem calls: struct fscache_volume * fscache_acquire_volume(const char *volume_key, const char *cache_name, const void *coherency_data, size_t coherency_len) The volume_key is a printable string used to match the volume in the cache. It should not contain any '/' characters. For AFS, for example, this would be "afs,<cellname>,<volume_id>", e.g. "afs,example.com,523001". The cache_name can be NULL, but if not it should be a string indicating the name of the cache to use if there's more than one available. The coherency data, if given, is an arbitrarily-sized blob that's attached to the volume and is compared when the volume is looked up. If it doesn't match, the old volume is judged to be out of date and it and everything within it is discarded. Acquiring a volume twice concurrently is disallowed, though the function will wait if an old volume cookie is being relinquishing. When a network filesystem has finished with a volume, it should return the volume cookie by calling: void fscache_relinquish_volume(struct fscache_volume *volume, const void *coherency_data, bool invalidate) If invalidate is true, the entire volume will be discarded; if false, the volume will be synced and the coherency data will be updated. Changes ======= ver #4: - Removed an extraneous param from kdoc on fscache_relinquish_volume()[3]. ver #3: - fscache_hash()'s size parameter is now in bytes. Use __le32 as the unit to round up to. - When comparing cookies, simply see if the attributes are the same rather than subtracting them to produce a strcmp-style return[2]. - Make the coherency data an arbitrary blob rather than a u64, but don't store it for the moment. ver #2: - Fix error check[1]. - Make a fscache_acquire_volume() return errors, including EBUSY if a conflicting volume cookie already exists. No error is printed now - that's left to the netfs. Signed-off-by: David Howells <dhowells@redhat.com> Reviewed-by: Jeff Layton <jlayton@kernel.org> cc: linux-cachefs@redhat.com Link: https://lore.kernel.org/r/20211203095608.GC2480@kili/ [1] Link: https://lore.kernel.org/r/CAHk-=whtkzB446+hX0zdLsdcUJsJ=8_-0S1mE_R+YurThfUbLA@mail.gmail.com/ [2] Link: https://lore.kernel.org/r/20211220224646.30e8205c@canb.auug.org.au/ [3] Link: https://lore.kernel.org/r/163819588944.215744.1629085755564865996.stgit@warthog.procyon.org.uk/ # v1 Link: https://lore.kernel.org/r/163906890630.143852.13972180614535611154.stgit@warthog.procyon.org.uk/ # v2 Link: https://lore.kernel.org/r/163967086836.1823006.8191672796841981763.stgit@warthog.procyon.org.uk/ # v3 Link: https://lore.kernel.org/r/164021495816.640689.4403156093668590217.stgit@warthog.procyon.org.uk/ # v4
Diffstat (limited to 'fs/fscache/Makefile')
-rw-r--r--fs/fscache/Makefile3
1 files changed, 2 insertions, 1 deletions
diff --git a/fs/fscache/Makefile b/fs/fscache/Makefile
index d9fc22c18090..bb5282ae682f 100644
--- a/fs/fscache/Makefile
+++ b/fs/fscache/Makefile
@@ -5,7 +5,8 @@
fscache-y := \
cache.o \
- main.o
+ main.o \
+ volume.o
fscache-$(CONFIG_PROC_FS) += proc.o
fscache-$(CONFIG_FSCACHE_STATS) += stats.o