[PATCH] FUSE - direct I/O
This patch adds support for the "direct_io" mount option of FUSE.
When this mount option is specified, the page cache is bypassed for
read and write operations. This is useful for example, if the
filesystem doesn't know the size of files before reading them, or when
any kind of caching is harmful.
Signed-off-by: Miklos Szeredi <miklos@szeredi.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
index 298c1d4..652c9d5 100644
--- a/fs/fuse/inode.c
+++ b/fs/fuse/inode.c
@@ -258,6 +258,7 @@
OPT_DEFAULT_PERMISSIONS,
OPT_ALLOW_OTHER,
OPT_KERNEL_CACHE,
+ OPT_DIRECT_IO,
OPT_MAX_READ,
OPT_ERR
};
@@ -270,6 +271,7 @@
{OPT_DEFAULT_PERMISSIONS, "default_permissions"},
{OPT_ALLOW_OTHER, "allow_other"},
{OPT_KERNEL_CACHE, "kernel_cache"},
+ {OPT_DIRECT_IO, "direct_io"},
{OPT_MAX_READ, "max_read=%u"},
{OPT_ERR, NULL}
};
@@ -329,6 +331,10 @@
d->flags |= FUSE_KERNEL_CACHE;
break;
+ case OPT_DIRECT_IO:
+ d->flags |= FUSE_DIRECT_IO;
+ break;
+
case OPT_MAX_READ:
if (match_int(&args[0], &value))
return 0;
@@ -359,6 +365,8 @@
seq_puts(m, ",allow_other");
if (fc->flags & FUSE_KERNEL_CACHE)
seq_puts(m, ",kernel_cache");
+ if (fc->flags & FUSE_DIRECT_IO)
+ seq_puts(m, ",direct_io");
if (fc->max_read != ~0)
seq_printf(m, ",max_read=%u", fc->max_read);
return 0;
@@ -489,6 +497,7 @@
fc->max_read = d.max_read;
if (fc->max_read / PAGE_CACHE_SIZE < fc->bdi.ra_pages)
fc->bdi.ra_pages = fc->max_read / PAGE_CACHE_SIZE;
+ fc->max_write = FUSE_MAX_IN / 2;
err = -ENOMEM;
root = get_root_inode(sb, d.rootmode);