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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 /fs/cachefiles/io.c | |
| 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 'fs/cachefiles/io.c')
| -rw-r--r-- | fs/cachefiles/io.c | 15 |
1 files changed, 13 insertions, 2 deletions
diff --git a/fs/cachefiles/io.c b/fs/cachefiles/io.c index 50a14e8f0aac..000a28f46e59 100644 --- a/fs/cachefiles/io.c +++ b/fs/cachefiles/io.c @@ -403,6 +403,7 @@ static enum netfs_io_source cachefiles_prepare_read(struct netfs_io_subrequest * enum netfs_io_source ret = NETFS_DOWNLOAD_FROM_SERVER; loff_t off, to; ino_t ino = file ? file_inode(file)->i_ino : 0; + int rc; _enter("%zx @%llx/%llx", subreq->len, subreq->start, i_size); @@ -415,7 +416,8 @@ static enum netfs_io_source cachefiles_prepare_read(struct netfs_io_subrequest * if (test_bit(FSCACHE_COOKIE_NO_DATA_TO_READ, &cookie->flags)) { __set_bit(NETFS_SREQ_COPY_TO_CACHE, &subreq->flags); why = cachefiles_trace_read_no_data; - goto out_no_object; + if (!test_bit(NETFS_SREQ_ONDEMAND, &subreq->flags)) + goto out_no_object; } /* The object and the file may be being created in the background. */ @@ -432,7 +434,7 @@ static enum netfs_io_source cachefiles_prepare_read(struct netfs_io_subrequest * object = cachefiles_cres_object(cres); cache = object->volume->cache; cachefiles_begin_secure(cache, &saved_cred); - +retry: off = cachefiles_inject_read_error(); if (off == 0) off = vfs_llseek(file, subreq->start, SEEK_DATA); @@ -483,6 +485,15 @@ static enum netfs_io_source cachefiles_prepare_read(struct netfs_io_subrequest * download_and_store: __set_bit(NETFS_SREQ_COPY_TO_CACHE, &subreq->flags); + if (test_bit(NETFS_SREQ_ONDEMAND, &subreq->flags)) { + rc = cachefiles_ondemand_read(object, subreq->start, + subreq->len); + if (!rc) { + __clear_bit(NETFS_SREQ_ONDEMAND, &subreq->flags); + goto retry; + } + ret = NETFS_INVALID_READ; + } out: cachefiles_end_secure(cache, saved_cred); out_no_object: |