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Subject[PATCH 4/7] FUSE: implement direct lseek support
Date
Allow clients to implement private lseek.  The feature is negotiated
using FUSE_DIRECT_LSEEK flag during INIT. If the client doesn't
request direct lseek, the original implicit lseek is used.

Signed-off-by: Tejun Heo <tj@kernel.org>
---
fs/fuse/file.c | 52 ++++++++++++++++++++++++++++++++++++++++++-------
fs/fuse/fuse_i.h | 3 ++
fs/fuse/inode.c | 4 ++-
include/linux/fuse.h | 14 +++++++++++++
4 files changed, 64 insertions(+), 9 deletions(-)

diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index 9c44f9c..fa27edb 100644
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -1448,18 +1448,53 @@ static sector_t fuse_bmap(struct address_space *mapping, sector_t block)

static loff_t fuse_file_llseek(struct file *file, loff_t offset, int origin)
{
- loff_t retval;
+ loff_t retval = -EINVAL;
struct inode *inode = file->f_path.dentry->d_inode;
+ struct fuse_conn *fc = get_fuse_conn(inode);
+
+ if (is_bad_inode(inode))
+ return -EIO;

mutex_lock(&inode->i_mutex);
- switch (origin) {
- case SEEK_END:
- offset += i_size_read(inode);
- break;
- case SEEK_CUR:
- offset += file->f_pos;
+
+ if (fc->direct_lseek) {
+ struct fuse_file *ff = file->private_data;
+ struct fuse_lseek_in inarg = { .fh = ff->fh, .pos = file->f_pos,
+ .offset = offset, .origin = origin };
+ struct fuse_lseek_out outarg;
+ struct fuse_req *req;
+ int err;
+
+ req = fuse_get_req(fc);
+ if (IS_ERR(req))
+ return PTR_ERR(req);
+
+ req->in.h.opcode = FUSE_LSEEK;
+ req->in.h.nodeid = get_node_id(inode);
+ req->in.numargs = 1;
+ req->in.args[0].size = sizeof(inarg);
+ req->in.args[0].value = &inarg;
+ req->out.numargs = 1;
+ req->out.args[0].size = sizeof(outarg);
+ req->out.args[0].value = &outarg;
+ request_send(fc, req);
+ err = req->out.h.error;
+ fuse_put_request(fc, req);
+
+ if (err)
+ return err;
+
+ offset = outarg.pos;
+ } else {
+ switch (origin) {
+ case SEEK_END:
+ offset += i_size_read(inode);
+ break;
+ case SEEK_CUR:
+ offset += file->f_pos;
+ }
}
- retval = -EINVAL;
+
if (offset >= 0 && offset <= inode->i_sb->s_maxbytes) {
if (offset != file->f_pos) {
file->f_pos = offset;
@@ -1467,6 +1502,7 @@ static loff_t fuse_file_llseek(struct file *file, loff_t offset, int origin)
}
retval = offset;
}
+
mutex_unlock(&inode->i_mutex);
return retval;
}
diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h
index e2b3b72..2bf2209 100644
--- a/fs/fuse/fuse_i.h
+++ b/fs/fuse/fuse_i.h
@@ -366,6 +366,9 @@ struct fuse_conn {
/** Do not send separate SETATTR request before open(O_TRUNC) */
unsigned atomic_o_trunc : 1;

+ /** Do direct lseek */
+ unsigned direct_lseek : 1;
+
/** Filesystem supports NFS exporting. Only set in INIT */
unsigned export_support : 1;

diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
index d2249f1..7693dfc 100644
--- a/fs/fuse/inode.c
+++ b/fs/fuse/inode.c
@@ -757,6 +757,8 @@ static void process_init_reply(struct fuse_conn *fc, struct fuse_req *req)
}
if (arg->flags & FUSE_BIG_WRITES)
fc->big_writes = 1;
+ if (arg->flags & FUSE_DIRECT_LSEEK)
+ fc->direct_lseek = 1;
} else {
ra_pages = fc->max_read / PAGE_CACHE_SIZE;
fc->no_lock = 1;
@@ -781,7 +783,7 @@ static void fuse_send_init(struct fuse_conn *fc, struct fuse_req *req)
arg->minor = FUSE_KERNEL_MINOR_VERSION;
arg->max_readahead = fc->bdi.ra_pages * PAGE_CACHE_SIZE;
arg->flags |= FUSE_ASYNC_READ | FUSE_POSIX_LOCKS | FUSE_ATOMIC_O_TRUNC |
- FUSE_EXPORT_SUPPORT | FUSE_BIG_WRITES;
+ FUSE_EXPORT_SUPPORT | FUSE_BIG_WRITES | FUSE_DIRECT_LSEEK;
req->in.h.opcode = FUSE_INIT;
req->in.numargs = 1;
req->in.args[0].size = sizeof(*arg);
diff --git a/include/linux/fuse.h b/include/linux/fuse.h
index 431666e..508d54e 100644
--- a/include/linux/fuse.h
+++ b/include/linux/fuse.h
@@ -118,6 +118,7 @@ struct fuse_file_lock {
#define FUSE_ATOMIC_O_TRUNC (1 << 3)
#define FUSE_EXPORT_SUPPORT (1 << 4)
#define FUSE_BIG_WRITES (1 << 5)
+#define FUSE_DIRECT_LSEEK (1 << 6)

/**
* Release flags
@@ -188,6 +189,7 @@ enum fuse_opcode {
FUSE_INTERRUPT = 36,
FUSE_BMAP = 37,
FUSE_DESTROY = 38,
+ FUSE_LSEEK = 39,
};

/* The read buffer is required to be at least 8k, but may be much larger */
@@ -388,6 +390,18 @@ struct fuse_bmap_out {
__u64 block;
};

+struct fuse_lseek_in {
+ __u64 fh;
+ __u64 pos; /* current file position */
+ __u64 offset; /* seek offset */
+ __u32 origin; /* SEEK_* */
+ __u32 padding;
+};
+
+struct fuse_lseek_out {
+ __u64 pos; /* new position */
+};
+
struct fuse_in_header {
__u32 len;
__u32 opcode;
--
1.5.4.5


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