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Date: Fri, 15 Jan 2016 10:57:15 +0530
From: Ravishankar N <ravishankar@...hat.com>
To: torvalds@...ux-foundation.org, david@...morbit.com,
viro@...iv.linux.org.uk
Cc: linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
fuse-devel@...ts.sourceforge.net,
Ravishankar N <ravishankar@...hat.com>,
Miklos Szeredi <miklos@...redi.hu>
Subject: [PATCH] fuse: add support for SEEK_HOLE and SEEK_DATA in lseek
A useful performance improvement for accessing virtual machine images
via FUSE mount.
See https://bugzilla.redhat.com/show_bug.cgi?id=1220173 for a use-case
for glusterFS.
Signed-off-by: Ravishankar N <ravishankar@...hat.com>
Signed-off-by: Miklos Szeredi <miklos@...redi.hu>
---
fs/fuse/file.c | 73 +++++++++++++++++++++++++++++++++++++++++------
fs/fuse/fuse_i.h | 3 ++
include/uapi/linux/fuse.h | 17 ++++++++++-
3 files changed, 84 insertions(+), 9 deletions(-)
diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index 570ca40..aa03aab 100644
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -2231,20 +2231,77 @@ static sector_t fuse_bmap(struct address_space *mapping, sector_t block)
return err ? 0 : outarg.block;
}
+static loff_t fuse_lseek(struct file *file, loff_t offset, int whence)
+{
+ struct inode *inode = file->f_mapping->host;
+ struct fuse_conn *fc = get_fuse_conn(inode);
+ struct fuse_file *ff = file->private_data;
+ FUSE_ARGS(args);
+ struct fuse_lseek_in inarg = {
+ .fh = ff->fh,
+ .offset = offset,
+ .whence = whence
+ };
+ struct fuse_lseek_out outarg;
+ int err;
+
+ if (fc->no_lseek)
+ goto fallback;
+
+ args.in.h.opcode = FUSE_LSEEK;
+ args.in.h.nodeid = ff->nodeid;
+ args.in.numargs = 1;
+ args.in.args[0].size = sizeof(inarg);
+ args.in.args[0].value = &inarg;
+ args.out.numargs = 1;
+ args.out.args[0].size = sizeof(outarg);
+ args.out.args[0].value = &outarg;
+ err = fuse_simple_request(fc, &args);
+ if (err) {
+ if (err == -ENOSYS) {
+ fc->no_lseek = 1;
+ goto fallback;
+ }
+ return err;
+ }
+
+ return vfs_setpos(file, outarg.offset, inode->i_sb->s_maxbytes);
+
+fallback:
+ err = fuse_update_attributes(inode, NULL, file, NULL);
+ if (!err)
+ return generic_file_llseek(file, offset, whence);
+ else
+ return err;
+}
+
static loff_t fuse_file_llseek(struct file *file, loff_t offset, int whence)
{
loff_t retval;
struct inode *inode = file_inode(file);
- /* No i_mutex protection necessary for SEEK_CUR and SEEK_SET */
- if (whence == SEEK_CUR || whence == SEEK_SET)
- return generic_file_llseek(file, offset, whence);
-
- mutex_lock(&inode->i_mutex);
- retval = fuse_update_attributes(inode, NULL, file, NULL);
- if (!retval)
+ switch (whence) {
+ case SEEK_SET:
+ case SEEK_CUR:
+ /* No i_mutex protection necessary for SEEK_CUR and SEEK_SET */
retval = generic_file_llseek(file, offset, whence);
- mutex_unlock(&inode->i_mutex);
+ break;
+ case SEEK_END:
+ mutex_lock(&inode->i_mutex);
+ retval = fuse_update_attributes(inode, NULL, file, NULL);
+ if (!retval)
+ retval = generic_file_llseek(file, offset, whence);
+ mutex_unlock(&inode->i_mutex);
+ break;
+ case SEEK_HOLE:
+ case SEEK_DATA:
+ mutex_lock(&inode->i_mutex);
+ retval = fuse_lseek(file, offset, whence);
+ mutex_unlock(&inode->i_mutex);
+ break;
+ default:
+ retval = -EINVAL;
+ }
return retval;
}
diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h
index 4051131..ce394b5 100644
--- a/fs/fuse/fuse_i.h
+++ b/fs/fuse/fuse_i.h
@@ -605,6 +605,9 @@ struct fuse_conn {
/** Does the filesystem support asynchronous direct-IO submission? */
unsigned async_dio:1;
+ /** Is lseek not implemented by fs? */
+ unsigned no_lseek:1;
+
/** The number of requests waiting for completion */
atomic_t num_waiting;
diff --git a/include/uapi/linux/fuse.h b/include/uapi/linux/fuse.h
index c9aca04..5974fae 100644
--- a/include/uapi/linux/fuse.h
+++ b/include/uapi/linux/fuse.h
@@ -102,6 +102,9 @@
* - add ctime and ctimensec to fuse_setattr_in
* - add FUSE_RENAME2 request
* - add FUSE_NO_OPEN_SUPPORT flag
+ *
+ * 7.24
+ * - add FUSE_LSEEK for SEEK_HOLE and SEEK_DATA support
*/
#ifndef _LINUX_FUSE_H
@@ -137,7 +140,7 @@
#define FUSE_KERNEL_VERSION 7
/** Minor version number of this interface */
-#define FUSE_KERNEL_MINOR_VERSION 23
+#define FUSE_KERNEL_MINOR_VERSION 24
/** The node ID of the root inode */
#define FUSE_ROOT_ID 1
@@ -358,6 +361,7 @@ enum fuse_opcode {
FUSE_FALLOCATE = 43,
FUSE_READDIRPLUS = 44,
FUSE_RENAME2 = 45,
+ FUSE_LSEEK = 46,
/* CUSE specific operations */
CUSE_INIT = 4096,
@@ -758,4 +762,15 @@ struct fuse_notify_retrieve_in {
/* Device ioctls: */
#define FUSE_DEV_IOC_CLONE _IOR(229, 0, uint32_t)
+struct fuse_lseek_in {
+ uint64_t fh;
+ uint64_t offset;
+ uint32_t whence;
+ uint32_t padding;
+};
+
+struct fuse_lseek_out {
+ uint64_t offset;
+};
+
#endif /* _LINUX_FUSE_H */
--
2.5.0
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