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| author | Jeffle Xu <jefflexu@linux.alibaba.com> | 2022-04-25 20:21:27 +0800 |
|---|---|---|
| committer | Gao Xiang <hsiangkao@linux.alibaba.com> | 2022-05-18 00:11:18 +0800 |
| commit | 9032b6e8589f269743984aac53e82e4835be16dc (patch) | |
| tree | cc6b3220d27164f6b39d343a60f5412786db8181 /include/linux/netfs.h | |
| parent | 324b954ac80cff0d11ddb6bde9b6631e45e98620 (diff) | |
| download | linux-9032b6e8589f269743984aac53e82e4835be16dc.tar.bz2 | |
cachefiles: implement on-demand read
Implement the data plane of on-demand read mode.
The early implementation [1] place the entry to
cachefiles_ondemand_read() in fscache_read(). However, fscache_read()
can only detect if the requested file range is fully cache miss, whilst
we need to notify the user daemon as long as there's a hole inside the
requested file range.
Thus the entry is now placed in cachefiles_prepare_read(). When working
in on-demand read mode, once a hole detected, the read routine will send
a READ request to the user daemon. The user daemon needs to fetch the
data and write it to the cache file. After sending the READ request, the
read routine will hang there, until the READ request is handled by the
user daemon. Then it will retry to read from the same file range. If no
progress encountered, the read routine will fail then.
A new NETFS_SREQ_ONDEMAND flag is introduced to indicate that on-demand
read should be done when a cache miss encountered.
[1] https://lore.kernel.org/all/20220406075612.60298-6-jefflexu@linux.alibaba.com/ #v8
Signed-off-by: Jeffle Xu <jefflexu@linux.alibaba.com>
Acked-by: David Howells <dhowells@redhat.com>
Link: https://lore.kernel.org/r/20220425122143.56815-6-jefflexu@linux.alibaba.com
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Diffstat (limited to 'include/linux/netfs.h')
| -rw-r--r-- | include/linux/netfs.h | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/include/linux/netfs.h b/include/linux/netfs.h index c7bf1eaf51d5..057d04efaf79 100644 --- a/include/linux/netfs.h +++ b/include/linux/netfs.h @@ -159,6 +159,7 @@ struct netfs_io_subrequest { #define NETFS_SREQ_SHORT_IO 2 /* Set if the I/O was short */ #define NETFS_SREQ_SEEK_DATA_READ 3 /* Set if ->read() should SEEK_DATA first */ #define NETFS_SREQ_NO_PROGRESS 4 /* Set if we didn't manage to read any data */ +#define NETFS_SREQ_ONDEMAND 5 /* Set if it's from on-demand read mode */ }; enum netfs_io_origin { |