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/ioctl.c b/fs/nilfs2/ioctl.c
index f2469ba..6f61777 100644 (file)
--- a/fs/nilfs2/ioctl.c
+++ b/fs/nilfs2/ioctl.c
@@ -698,6 +698,38 @@ static int nilfs_ioctl_sync(struct inode *inode, struct file *filp,
        return 0;
 }
 
+static int nilfs_ioctl_set_alloc_range(struct inode *inode, void __user *argp)
+{
+       struct the_nilfs *nilfs = inode->i_sb->s_fs_info;
+       __u64 range[2];
+       __u64 minseg, maxseg;
+       unsigned long segbytes;
+       int ret = -EPERM;
+
+       if (!capable(CAP_SYS_ADMIN))
+               goto out;
+
+       ret = -EFAULT;
+       if (copy_from_user(range, argp, sizeof(__u64[2])))
+               goto out;
+
+       ret = -ERANGE;
+       if (range[1] > i_size_read(inode->i_sb->s_bdev->bd_inode))
+               goto out;
+
+       segbytes = nilfs->ns_blocks_per_segment * nilfs->ns_blocksize;
+
+       minseg = range[0] + segbytes - 1;
+       do_div(minseg, segbytes);
+       maxseg = NILFS_SB2_OFFSET_BYTES(range[1]);
+       do_div(maxseg, segbytes);
+       maxseg--;
+
+       ret = nilfs_sufile_set_alloc_range(nilfs->ns_sufile, minseg, maxseg);
+out:
+       return ret;
+}
+
 static int nilfs_ioctl_get_info(struct inode *inode, struct file *filp,
                                unsigned int cmd, void __user *argp,
                                size_t membsz,
@@ -763,6 +795,8 @@ long nilfs_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
                return nilfs_ioctl_clean_segments(inode, filp, cmd, argp);
        case NILFS_IOCTL_SYNC:
                return nilfs_ioctl_sync(inode, filp, cmd, argp);
+       case NILFS_IOCTL_SET_ALLOC_RANGE:
+               return nilfs_ioctl_set_alloc_range(inode, argp);
        default:
                return -ENOTTY;
        }

diff --git a/fs/nilfs2/sufile.c b/fs/nilfs2/sufile.c
index 1d6f488..f4374df 100644 (file)
--- 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)
@@ -247,6 +249,35 @@ int nilfs_sufile_update(struct inode *sufile, __u64 segnum, int create,
        return ret;
 }
 
+/**
+ * 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
@@ -269,11 +300,12 @@ int nilfs_sufile_alloc(struct inode *sufile, __u64 *segnump)
        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 @@ int nilfs_sufile_alloc(struct inode *sufile, __u64 *segnump)
        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 @@ int nilfs_sufile_alloc(struct inode *sufile, __u64 *segnump)
                        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 @@ int nilfs_sufile_read(struct super_block *sb, size_t susize,
        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;

diff --git a/fs/nilfs2/sufile.h b/fs/nilfs2/sufile.h
index a943fba..57bfee9 100644 (file)
--- a/fs/nilfs2/sufile.h
+++ b/fs/nilfs2/sufile.h
@@ -36,6 +36,7 @@ static inline unsigned long nilfs_sufile_get_nsegments(struct inode *sufile)
 
 unsigned long nilfs_sufile_get_ncleansegs(struct inode *sufile);
 
+int nilfs_sufile_set_alloc_range(struct inode *sufile, __u64 start, __u64 end);
 int nilfs_sufile_alloc(struct inode *, __u64 *);
 int nilfs_sufile_mark_dirty(struct inode *sufile, __u64 segnum);
 int nilfs_sufile_set_segment_usage(struct inode *sufile, __u64 segnum,

diff --git a/include/linux/nilfs2_fs.h b/include/linux/nilfs2_fs.h
index bd8678f..7454ad7 100644 (file)
--- a/include/linux/nilfs2_fs.h
+++ b/include/linux/nilfs2_fs.h
@@ -845,5 +845,7 @@ struct nilfs_bdesc {
        _IOR(NILFS_IOCTL_IDENT, 0x8A, __u64)
 #define NILFS_IOCTL_RESIZE  \
        _IOW(NILFS_IOCTL_IDENT, 0x8B, __u64)
+#define NILFS_IOCTL_SET_ALLOC_RANGE  \
+       _IOW(NILFS_IOCTL_IDENT, 0x8C, __u64[2])
 
 #endif /* _LINUX_NILFS_FS_H */