path: root/api
diff options
authorM. Mohan Kumar <>2013-11-09 14:51:53 +0530
committerVijay Bellur <>2013-11-10 21:25:49 -0800
commitc8fef37c5d566c906728b5f6f27baaa9a8d2a20d (patch)
tree03c833446bc73bfa3da6c621315b590c0d65c748 /api
parentd5335f9e40f6e9533f7812d153b9727bcc04aa4e (diff)
glusterfs: zerofill support
Add support for a new ZEROFILL fop. Zerofill writes zeroes to a file in the specified range. This fop will be useful when a whole file needs to be initialized with zero (could be useful for zero filled VM disk image provisioning or during scrubbing of VM disk images). Client/application can issue this FOP for zeroing out. Gluster server will zero out required range of bytes ie server offloaded zeroing. In the absence of this fop, client/application has to repetitively issue write (zero) fop to the server, which is very inefficient method because of the overheads involved in RPC calls and acknowledgements. WRITESAME is a SCSI T10 command that takes a block of data as input and writes the same data to other blocks and this write is handled completely within the storage and hence is known as offload . Linux ,now has support for SCSI WRITESAME command which is exposed to the user in the form of BLKZEROOUT ioctl. BD Xlator can exploit BLKZEROOUT ioctl to implement this fop. Thus zeroing out operations can be completely offloaded to the storage device , making it highly efficient. The fop takes two arguments offset and size. It zeroes out 'size' number of bytes in an opened file starting from 'offset' position. This patch adds zerofill support to the following areas: - libglusterfs - io-stats - performance/md-cache,open-behind - quota - cluster/afr,dht,stripe - rpc/xdr - protocol/client,server - io-threads - marker - storage/posix - libgfapi Client applications can exloit this fop by using glfs_zerofill introduced in libgfapi.FUSE support to this fop has not been added as there is no system call for this fop. Changes from previous version 3: * Removed redundant memory failure log messages Changes from previous version 2: * Rebased and fixed build error Changes from previous version 1: * Rebased for latest master TODO : * Add zerofill support to trace xlator * Expose zerofill capability as part of gluster volume info Here is a performance comparison of server offloaded zeofill vs zeroing out using repeated writes. [root@llmvm02 remote]# time ./offloaded aakash-test log 20 real 3m34.155s user 0m0.018s sys 0m0.040s [root@llmvm02 remote]# time ./manually aakash-test log 20 real 4m23.043s user 0m2.197s sys 0m14.457s [root@llmvm02 remote]# time ./offloaded aakash-test log 25; real 4m28.363s user 0m0.021s sys 0m0.025s [root@llmvm02 remote]# time ./manually aakash-test log 25 real 5m34.278s user 0m2.957s sys 0m18.808s The argument log is a file which we want to set for logging purpose and the third argument is size in GB . As we can see there is a performance improvement of around 20% with this fop. Change-Id: I081159f5f7edde0ddb78169fb4c21c776ec91a18 BUG: 1028673 Signed-off-by: Aakash Lal Das <> Signed-off-by: M. Mohan Kumar <> Reviewed-on: Tested-by: Gluster Build System <> Reviewed-by: Vijay Bellur <>
Diffstat (limited to 'api')
2 files changed, 71 insertions, 0 deletions
diff --git a/api/src/glfs-fops.c b/api/src/glfs-fops.c
index 9070661b9..7572a94f2 100644
--- a/api/src/glfs-fops.c
+++ b/api/src/glfs-fops.c
@@ -591,6 +591,9 @@ glfs_io_async_task (void *data)
ret = glfs_discard (gio->glfd, gio->offset, gio->count);
+ ret = glfs_zerofill(gio->glfd, gio->offset, gio->count);
+ break;
return (int) ret;
@@ -1865,6 +1868,38 @@ glfs_discard_async (struct glfs_fd *glfd, off_t offset, size_t len,
return ret;
+glfs_zerofill_async (struct glfs_fd *glfd, off_t offset, size_t len,
+ glfs_io_cbk fn, void *data)
+ struct glfs_io *gio = NULL;
+ int ret = 0;
+ gio = GF_CALLOC (1, sizeof (*gio), glfs_mt_glfs_io_t);
+ if (!gio) {
+ errno = ENOMEM;
+ return -1;
+ }
+ gio->op = GF_FOP_ZEROFILL;
+ gio->glfd = glfd;
+ gio->offset = offset;
+ gio->count = len;
+ gio->fn = fn;
+ gio->data = data;
+ ret = synctask_new (glfs_from_glfd (glfd)->ctx->env,
+ glfs_io_async_task, glfs_io_async_cbk,
+ NULL, gio);
+ if (ret) {
+ GF_FREE (gio->iov);
+ GF_FREE (gio);
+ }
+ return ret;
gf_dirent_to_dirent (gf_dirent_t *gf_dirent, struct dirent *dirent)
@@ -2821,6 +2856,36 @@ out:
return ret;
+glfs_zerofill (struct glfs_fd *glfd, off_t offset, size_t len)
+ int ret = -1;
+ xlator_t *subvol = NULL;
+ fd_t *fd = NULL;
+ __glfs_entry_fd (glfd);
+ subvol = glfs_active_subvol (glfd->fs);
+ if (!subvol) {
+ errno = EIO;
+ goto out;
+ }
+ fd = glfs_resolve_fd (glfd->fs, subvol, glfd);
+ if (!fd) {
+ errno = EBADFD;
+ goto out;
+ }
+ ret = syncop_zerofill (subvol, fd, offset, len);
+ if (fd)
+ fd_unref(fd);
+ glfs_subvol_done (glfd->fs, subvol);
+ return ret;
glfs_chdir (struct glfs *fs, const char *path)
diff --git a/api/src/glfs.h b/api/src/glfs.h
index c2fb26505..d179b87ba 100644
--- a/api/src/glfs.h
+++ b/api/src/glfs.h
@@ -533,9 +533,15 @@ int glfs_fallocate(glfs_fd_t *fd, int keep_size, off_t offset, size_t len);
int glfs_discard(glfs_fd_t *fd, off_t offset, size_t len);
int glfs_discard_async (glfs_fd_t *fd, off_t length, size_t lent,
glfs_io_cbk fn, void *data);
+int glfs_zerofill(glfs_fd_t *fd, off_t offset, size_t len);
+int glfs_zerofill_async (glfs_fd_t *fd, off_t length, size_t len,
+ glfs_io_cbk fn, void *data);
char *glfs_getcwd (glfs_t *fs, char *buf, size_t size);
int glfs_chdir (glfs_t *fs, const char *path);