nilfs2: add ioctl which limits range of segment to be allocated
This adds a new ioctl command which limits range of segment to be
allocated. This is intended to gather data whithin a range of the
partition before shrinking the filesystem, or to control new log
location for some purpose.
If a range is specified by the ioctl, segment allocator of nilfs tries
to allocate new segments from the range unless no free segments are
available there.
Signed-off-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
diff --git a/fs/nilfs2/sufile.c b/fs/nilfs2/sufile.c
index 1d6f488..f4374df 100644
--- a/fs/nilfs2/sufile.c
+++ b/fs/nilfs2/sufile.c
@@ -33,7 +33,9 @@
struct nilfs_sufile_info {
struct nilfs_mdt_info mi;
- unsigned long ncleansegs;
+ unsigned long ncleansegs;/* number of clean segments */
+ __u64 allocmin; /* lower limit of allocatable segment range */
+ __u64 allocmax; /* upper limit of allocatable segment range */
};
static inline struct nilfs_sufile_info *NILFS_SUI(struct inode *sufile)
@@ -248,6 +250,35 @@
}
/**
+ * nilfs_sufile_set_alloc_range - limit range of segment to be allocated
+ * @sufile: inode of segment usage file
+ * @start: minimum segment number of allocatable region (inclusive)
+ * @end: maximum segment number of allocatable region (inclusive)
+ *
+ * Return Value: On success, 0 is returned. On error, one of the
+ * following negative error codes is returned.
+ *
+ * %-ERANGE - invalid segment region
+ */
+int nilfs_sufile_set_alloc_range(struct inode *sufile, __u64 start, __u64 end)
+{
+ struct nilfs_sufile_info *sui = NILFS_SUI(sufile);
+ __u64 nsegs;
+ int ret = -ERANGE;
+
+ down_write(&NILFS_MDT(sufile)->mi_sem);
+ nsegs = nilfs_sufile_get_nsegments(sufile);
+
+ if (start <= end && end < nsegs) {
+ sui->allocmin = start;
+ sui->allocmax = end;
+ ret = 0;
+ }
+ up_write(&NILFS_MDT(sufile)->mi_sem);
+ return ret;
+}
+
+/**
* nilfs_sufile_alloc - allocate a segment
* @sufile: inode of segment usage file
* @segnump: pointer to segment number
@@ -269,11 +300,12 @@
struct buffer_head *header_bh, *su_bh;
struct nilfs_sufile_header *header;
struct nilfs_segment_usage *su;
+ struct nilfs_sufile_info *sui = NILFS_SUI(sufile);
size_t susz = NILFS_MDT(sufile)->mi_entry_size;
__u64 segnum, maxsegnum, last_alloc;
void *kaddr;
- unsigned long nsegments, ncleansegs, nsus;
- int ret, i, j;
+ unsigned long nsegments, ncleansegs, nsus, cnt;
+ int ret, j;
down_write(&NILFS_MDT(sufile)->mi_sem);
@@ -287,13 +319,31 @@
kunmap_atomic(kaddr, KM_USER0);
nsegments = nilfs_sufile_get_nsegments(sufile);
+ maxsegnum = sui->allocmax;
segnum = last_alloc + 1;
- maxsegnum = nsegments - 1;
- for (i = 0; i < nsegments; i += nsus) {
- if (segnum >= nsegments) {
- /* wrap around */
- segnum = 0;
- maxsegnum = last_alloc;
+ if (segnum < sui->allocmin || segnum > sui->allocmax)
+ segnum = sui->allocmin;
+
+ for (cnt = 0; cnt < nsegments; cnt += nsus) {
+ if (segnum > maxsegnum) {
+ if (cnt < sui->allocmax - sui->allocmin + 1) {
+ /*
+ * wrap around in the limited region.
+ * if allocation started from
+ * sui->allocmin, this never happens.
+ */
+ segnum = sui->allocmin;
+ maxsegnum = last_alloc;
+ } else if (segnum > sui->allocmin &&
+ sui->allocmax + 1 < nsegments) {
+ segnum = sui->allocmax + 1;
+ maxsegnum = nsegments - 1;
+ } else if (sui->allocmin > 0) {
+ segnum = 0;
+ maxsegnum = sui->allocmin - 1;
+ } else {
+ break; /* never happens */
+ }
}
ret = nilfs_sufile_get_segment_usage_block(sufile, segnum, 1,
&su_bh);
@@ -319,7 +369,7 @@
header->sh_last_alloc = cpu_to_le64(segnum);
kunmap_atomic(kaddr, KM_USER0);
- NILFS_SUI(sufile)->ncleansegs--;
+ sui->ncleansegs--;
nilfs_mdt_mark_buffer_dirty(header_bh);
nilfs_mdt_mark_buffer_dirty(su_bh);
nilfs_mdt_mark_dirty(sufile);
@@ -679,6 +729,9 @@
kunmap_atomic(kaddr, KM_USER0);
brelse(header_bh);
+ sui->allocmax = nilfs_sufile_get_nsegments(sufile) - 1;
+ sui->allocmin = 0;
+
unlock_new_inode(sufile);
out:
*inodep = sufile;