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Diffstat (limited to 'Documentation/filesystems/fuse-io.txt')
| -rw-r--r-- | Documentation/filesystems/fuse-io.txt | 38 |
1 files changed, 0 insertions, 38 deletions
diff --git a/Documentation/filesystems/fuse-io.txt b/Documentation/filesystems/fuse-io.txt deleted file mode 100644 index 07b8f73f100f..000000000000 --- a/Documentation/filesystems/fuse-io.txt +++ /dev/null @@ -1,38 +0,0 @@ -Fuse supports the following I/O modes: - -- direct-io -- cached - + write-through - + writeback-cache - -The direct-io mode can be selected with the FOPEN_DIRECT_IO flag in the -FUSE_OPEN reply. - -In direct-io mode the page cache is completely bypassed for reads and writes. -No read-ahead takes place. Shared mmap is disabled. - -In cached mode reads may be satisfied from the page cache, and data may be -read-ahead by the kernel to fill the cache. The cache is always kept consistent -after any writes to the file. All mmap modes are supported. - -The cached mode has two sub modes controlling how writes are handled. The -write-through mode is the default and is supported on all kernels. The -writeback-cache mode may be selected by the FUSE_WRITEBACK_CACHE flag in the -FUSE_INIT reply. - -In write-through mode each write is immediately sent to userspace as one or more -WRITE requests, as well as updating any cached pages (and caching previously -uncached, but fully written pages). No READ requests are ever sent for writes, -so when an uncached page is partially written, the page is discarded. - -In writeback-cache mode (enabled by the FUSE_WRITEBACK_CACHE flag) writes go to -the cache only, which means that the write(2) syscall can often complete very -fast. Dirty pages are written back implicitly (background writeback or page -reclaim on memory pressure) or explicitly (invoked by close(2), fsync(2) and -when the last ref to the file is being released on munmap(2)). This mode -assumes that all changes to the filesystem go through the FUSE kernel module -(size and atime/ctime/mtime attributes are kept up-to-date by the kernel), so -it's generally not suitable for network filesystems. If a partial page is -written, then the page needs to be first read from userspace. This means, that -even for files opened for O_WRONLY it is possible that READ requests will be -generated by the kernel. |