1 files changed, 248 insertions, 253 deletions

diff --git a/fs/nilfs2/segment.c b/fs/nilfs2/segment.c
index 6eff66a070d5..6a7dbd8451db 100644
--- a/fs/nilfs2/segment.c
+++ b/fs/nilfs2/segment.c
@@ -32,6 +32,7 @@
 #include <linux/kthread.h>
 #include <linux/crc32.h>
 #include <linux/pagevec.h>
+#include <linux/slab.h>
 #include "nilfs.h"
 #include "btnode.h"
 #include "page.h"
@@ -141,7 +142,7 @@ int nilfs_init_transaction_cache(void)
 }
 
 /**
- * nilfs_detroy_transaction_cache - destroy the cache for transaction info
+ * nilfs_destroy_transaction_cache - destroy the cache for transaction info
  *
  * nilfs_destroy_transaction_cache() frees the slab cache for the struct
  * nilfs_transaction_info.
@@ -201,7 +202,7 @@ static int nilfs_prepare_segment_lock(struct nilfs_transaction_info *ti)
  * This function allocates a nilfs_transaction_info struct to keep context
  * information on it.  It is initialized and hooked onto the current task in
  * the outermost call.  If a pre-allocated struct is given to @ti, it is used
- * instead; othewise a new struct is assigned from a slab.
+ * instead; otherwise a new struct is assigned from a slab.
  *
  * When @vacancy_check flag is set, this function will check the amount of
  * free space, and will wait for the GC to reclaim disk space if low capacity.
@@ -974,12 +975,12 @@ static void nilfs_segctor_fill_in_super_root(struct nilfs_sc_info *sci,
                               nilfs->ns_nongc_ctime : sci->sc_seg_ctime);
         raw_sr->sr_flags = 0;
 
-        nilfs_mdt_write_inode_direct(
-                nilfs_dat_inode(nilfs), bh_sr, NILFS_SR_DAT_OFFSET(isz));
-        nilfs_mdt_write_inode_direct(
-                nilfs->ns_cpfile, bh_sr, NILFS_SR_CPFILE_OFFSET(isz));
-        nilfs_mdt_write_inode_direct(
-                nilfs->ns_sufile, bh_sr, NILFS_SR_SUFILE_OFFSET(isz));
+        nilfs_write_inode_common(nilfs_dat_inode(nilfs), (void *)raw_sr +
+                                 NILFS_SR_DAT_OFFSET(isz), 1);
+        nilfs_write_inode_common(nilfs->ns_cpfile, (void *)raw_sr +
+                                 NILFS_SR_CPFILE_OFFSET(isz), 1);
+        nilfs_write_inode_common(nilfs->ns_sufile, (void *)raw_sr +
+                                 NILFS_SR_SUFILE_OFFSET(isz), 1);
 }
 
 static void nilfs_redirty_inodes(struct list_head *head)
@@ -1273,73 +1274,75 @@ static int nilfs_segctor_collect_blocks(struct nilfs_sc_info *sci, int mode)
         return err;
 }
 
-static int nilfs_touch_segusage(struct inode *sufile, __u64 segnum)
-{
-        struct buffer_head *bh_su;
-        struct nilfs_segment_usage *raw_su;
-        int err;
-
-        err = nilfs_sufile_get_segment_usage(sufile, segnum, &raw_su, &bh_su);
-        if (unlikely(err))
-                return err;
-        nilfs_mdt_mark_buffer_dirty(bh_su);
-        nilfs_mdt_mark_dirty(sufile);
-        nilfs_sufile_put_segment_usage(sufile, segnum, bh_su);
-        return 0;
-}
-
+/**
+ * nilfs_segctor_begin_construction - setup segment buffer to make a new log
+ * @sci: nilfs_sc_info
+ * @nilfs: nilfs object
+ */
 static int nilfs_segctor_begin_construction(struct nilfs_sc_info *sci,
                                             struct the_nilfs *nilfs)
 {
-        struct nilfs_segment_buffer *segbuf, *n;
+        struct nilfs_segment_buffer *segbuf, *prev;
         __u64 nextnum;
-        int err;
+        int err, alloc = 0;
 
-        if (list_empty(&sci->sc_segbufs)) {
-                segbuf = nilfs_segbuf_new(sci->sc_super);
-                if (unlikely(!segbuf))
-                        return -ENOMEM;
-                list_add(&segbuf->sb_list, &sci->sc_segbufs);
-        } else
-                segbuf = NILFS_FIRST_SEGBUF(&sci->sc_segbufs);
+        segbuf = nilfs_segbuf_new(sci->sc_super);
+        if (unlikely(!segbuf))
+                return -ENOMEM;
 
-        nilfs_segbuf_map(segbuf, nilfs->ns_segnum, nilfs->ns_pseg_offset,
-                         nilfs);
+        if (list_empty(&sci->sc_write_logs)) {
+                nilfs_segbuf_map(segbuf, nilfs->ns_segnum,
+                                 nilfs->ns_pseg_offset, nilfs);
+                if (segbuf->sb_rest_blocks < NILFS_PSEG_MIN_BLOCKS) {
+                        nilfs_shift_to_next_segment(nilfs);
+                        nilfs_segbuf_map(segbuf, nilfs->ns_segnum, 0, nilfs);
+                }
+
+                segbuf->sb_sum.seg_seq = nilfs->ns_seg_seq;
+                nextnum = nilfs->ns_nextnum;
 
-        if (segbuf->sb_rest_blocks < NILFS_PSEG_MIN_BLOCKS) {
-                nilfs_shift_to_next_segment(nilfs);
-                nilfs_segbuf_map(segbuf, nilfs->ns_segnum, 0, nilfs);
+                if (nilfs->ns_segnum == nilfs->ns_nextnum)
+                        /* Start from the head of a new full segment */
+                        alloc++;
+        } else {
+                /* Continue logs */
+                prev = NILFS_LAST_SEGBUF(&sci->sc_write_logs);
+                nilfs_segbuf_map_cont(segbuf, prev);
+                segbuf->sb_sum.seg_seq = prev->sb_sum.seg_seq;
+                nextnum = prev->sb_nextnum;
+
+                if (segbuf->sb_rest_blocks < NILFS_PSEG_MIN_BLOCKS) {
+                        nilfs_segbuf_map(segbuf, prev->sb_nextnum, 0, nilfs);
+                        segbuf->sb_sum.seg_seq++;
+                        alloc++;
+                }
         }
-        sci->sc_segbuf_nblocks = segbuf->sb_rest_blocks;
 
-        err = nilfs_touch_segusage(nilfs->ns_sufile, segbuf->sb_segnum);
-        if (unlikely(err))
-                return err;
+        err = nilfs_sufile_mark_dirty(nilfs->ns_sufile, segbuf->sb_segnum);
+        if (err)
+                goto failed;
 
-        if (nilfs->ns_segnum == nilfs->ns_nextnum) {
-                /* Start from the head of a new full segment */
+        if (alloc) {
                 err = nilfs_sufile_alloc(nilfs->ns_sufile, &nextnum);
-                if (unlikely(err))
-                        return err;
-        } else
-                nextnum = nilfs->ns_nextnum;
-
-        segbuf->sb_sum.seg_seq = nilfs->ns_seg_seq;
+                if (err)
+                        goto failed;
+        }
         nilfs_segbuf_set_next_segnum(segbuf, nextnum, nilfs);
 
-        /* truncating segment buffers */
-        list_for_each_entry_safe_continue(segbuf, n, &sci->sc_segbufs,
-                                          sb_list) {
-                list_del_init(&segbuf->sb_list);
-                nilfs_segbuf_free(segbuf);
-        }
+        BUG_ON(!list_empty(&sci->sc_segbufs));
+        list_add_tail(&segbuf->sb_list, &sci->sc_segbufs);
+        sci->sc_segbuf_nblocks = segbuf->sb_rest_blocks;
         return 0;
+
+ failed:
+        nilfs_segbuf_free(segbuf);
+        return err;
 }
 
 static int nilfs_segctor_extend_segments(struct nilfs_sc_info *sci,
                                          struct the_nilfs *nilfs, int nadd)
 {
-        struct nilfs_segment_buffer *segbuf, *prev, *n;
+        struct nilfs_segment_buffer *segbuf, *prev;
         struct inode *sufile = nilfs->ns_sufile;
         __u64 nextnextnum;
         LIST_HEAD(list);
@@ -1352,7 +1355,7 @@ static int nilfs_segctor_extend_segments(struct nilfs_sc_info *sci,
          * not be dirty.  The following call ensures that the buffer is dirty
          * and will pin the buffer on memory until the sufile is written.
          */
-        err = nilfs_touch_segusage(sufile, prev->sb_nextnum);
+        err = nilfs_sufile_mark_dirty(sufile, prev->sb_nextnum);
         if (unlikely(err))
                 return err;
 
@@ -1378,33 +1381,33 @@ static int nilfs_segctor_extend_segments(struct nilfs_sc_info *sci,
                 list_add_tail(&segbuf->sb_list, &list);
                 prev = segbuf;
         }
-        list_splice(&list, sci->sc_segbufs.prev);
+        list_splice_tail(&list, &sci->sc_segbufs);
         return 0;
 
  failed_segbuf:
         nilfs_segbuf_free(segbuf);
  failed:
-        list_for_each_entry_safe(segbuf, n, &list, sb_list) {
+        list_for_each_entry(segbuf, &list, sb_list) {
                 ret = nilfs_sufile_free(sufile, segbuf->sb_nextnum);
                 WARN_ON(ret); /* never fails */
-                list_del_init(&segbuf->sb_list);
-                nilfs_segbuf_free(segbuf);
         }
+        nilfs_destroy_logs(&list);
         return err;
 }
 
-static void nilfs_segctor_free_incomplete_segments(struct nilfs_sc_info *sci,
-                                                   struct the_nilfs *nilfs)
+static void nilfs_free_incomplete_logs(struct list_head *logs,
+                                       struct the_nilfs *nilfs)
 {
-        struct nilfs_segment_buffer *segbuf;
-        int ret, done = 0;
+        struct nilfs_segment_buffer *segbuf, *prev;
+        struct inode *sufile = nilfs->ns_sufile;
+        int ret;
 
-        segbuf = NILFS_FIRST_SEGBUF(&sci->sc_segbufs);
+        segbuf = NILFS_FIRST_SEGBUF(logs);
         if (nilfs->ns_nextnum != segbuf->sb_nextnum) {
-                ret = nilfs_sufile_free(nilfs->ns_sufile, segbuf->sb_nextnum);
+                ret = nilfs_sufile_free(sufile, segbuf->sb_nextnum);
                 WARN_ON(ret); /* never fails */
         }
-        if (segbuf->sb_io_error) {
+        if (atomic_read(&segbuf->sb_err)) {
                 /* Case 1: The first segment failed */
                 if (segbuf->sb_pseg_start != segbuf->sb_fseg_start)
                         /* Case 1a:  Partial segment appended into an existing
@@ -1413,106 +1416,54 @@ static void nilfs_segctor_free_incomplete_segments(struct nilfs_sc_info *sci,
                                                 segbuf->sb_fseg_end);
                 else /* Case 1b:  New full segment */
                         set_nilfs_discontinued(nilfs);
-                done++;
         }
 
-        list_for_each_entry_continue(segbuf, &sci->sc_segbufs, sb_list) {
-                ret = nilfs_sufile_free(nilfs->ns_sufile, segbuf->sb_nextnum);
-                WARN_ON(ret); /* never fails */
-                if (!done && segbuf->sb_io_error) {
-                        if (segbuf->sb_segnum != nilfs->ns_nextnum)
-                                /* Case 2: extended segment (!= next) failed */
-                                nilfs_sufile_set_error(nilfs->ns_sufile,
-                                                       segbuf->sb_segnum);
-                        done++;
-                }
-        }
-}
-
-static void nilfs_segctor_clear_segment_buffers(struct nilfs_sc_info *sci)
-{
-        struct nilfs_segment_buffer *segbuf;
-
-        list_for_each_entry(segbuf, &sci->sc_segbufs, sb_list)
-                nilfs_segbuf_clear(segbuf);
-        sci->sc_super_root = NULL;
-}
-
-static void nilfs_segctor_destroy_segment_buffers(struct nilfs_sc_info *sci)
-{
-        struct nilfs_segment_buffer *segbuf;
-
-        while (!list_empty(&sci->sc_segbufs)) {
-                segbuf = NILFS_FIRST_SEGBUF(&sci->sc_segbufs);
-                list_del_init(&segbuf->sb_list);
-                nilfs_segbuf_free(segbuf);
-        }
-        /* sci->sc_curseg = NULL; */
-}
-
-static void nilfs_segctor_end_construction(struct nilfs_sc_info *sci,
-                                           struct the_nilfs *nilfs, int err)
-{
-        if (unlikely(err)) {
-                nilfs_segctor_free_incomplete_segments(sci, nilfs);
-                if (sci->sc_stage.flags & NILFS_CF_SUFREED) {
-                        int ret;
-
-                        ret = nilfs_sufile_cancel_freev(nilfs->ns_sufile,
-                                                        sci->sc_freesegs,
-                                                        sci->sc_nfreesegs,
-                                                        NULL);
-                        WARN_ON(ret); /* do not happen */
+        prev = segbuf;
+        list_for_each_entry_continue(segbuf, logs, sb_list) {
+                if (prev->sb_nextnum != segbuf->sb_nextnum) {
+                        ret = nilfs_sufile_free(sufile, segbuf->sb_nextnum);
+                        WARN_ON(ret); /* never fails */
                 }
+                if (atomic_read(&segbuf->sb_err) &&
+                    segbuf->sb_segnum != nilfs->ns_nextnum)
+                        /* Case 2: extended segment (!= next) failed */
+                        nilfs_sufile_set_error(sufile, segbuf->sb_segnum);
+                prev = segbuf;
         }
-        nilfs_segctor_clear_segment_buffers(sci);
 }
 
 static void nilfs_segctor_update_segusage(struct nilfs_sc_info *sci,
                                           struct inode *sufile)
 {
         struct nilfs_segment_buffer *segbuf;
-        struct buffer_head *bh_su;
-        struct nilfs_segment_usage *raw_su;
         unsigned long live_blocks;
         int ret;
 
         list_for_each_entry(segbuf, &sci->sc_segbufs, sb_list) {
-                ret = nilfs_sufile_get_segment_usage(sufile, segbuf->sb_segnum,
-                                                     &raw_su, &bh_su);
-                WARN_ON(ret); /* always succeed because bh_su is dirty */
                 live_blocks = segbuf->sb_sum.nblocks +
                         (segbuf->sb_pseg_start - segbuf->sb_fseg_start);
-                raw_su->su_lastmod = cpu_to_le64(sci->sc_seg_ctime);
-                raw_su->su_nblocks = cpu_to_le32(live_blocks);
-                nilfs_sufile_put_segment_usage(sufile, segbuf->sb_segnum,
-                                               bh_su);
+                ret = nilfs_sufile_set_segment_usage(sufile, segbuf->sb_segnum,
+                                                     live_blocks,
+                                                     sci->sc_seg_ctime);
+                WARN_ON(ret); /* always succeed because the segusage is dirty */
         }
 }
 
-static void nilfs_segctor_cancel_segusage(struct nilfs_sc_info *sci,
-                                          struct inode *sufile)
+static void nilfs_cancel_segusage(struct list_head *logs, struct inode *sufile)
 {
         struct nilfs_segment_buffer *segbuf;
-        struct buffer_head *bh_su;
-        struct nilfs_segment_usage *raw_su;
         int ret;
 
-        segbuf = NILFS_FIRST_SEGBUF(&sci->sc_segbufs);
-        ret = nilfs_sufile_get_segment_usage(sufile, segbuf->sb_segnum,
-                                             &raw_su, &bh_su);
-        WARN_ON(ret); /* always succeed because bh_su is dirty */
-        raw_su->su_nblocks = cpu_to_le32(segbuf->sb_pseg_start -
-                                         segbuf->sb_fseg_start);
-        nilfs_sufile_put_segment_usage(sufile, segbuf->sb_segnum, bh_su);
+        segbuf = NILFS_FIRST_SEGBUF(logs);
+        ret = nilfs_sufile_set_segment_usage(sufile, segbuf->sb_segnum,
+                                             segbuf->sb_pseg_start -
+                                             segbuf->sb_fseg_start, 0);
+        WARN_ON(ret); /* always succeed because the segusage is dirty */
 
-        list_for_each_entry_continue(segbuf, &sci->sc_segbufs, sb_list) {
-                ret = nilfs_sufile_get_segment_usage(sufile, segbuf->sb_segnum,
-                                                     &raw_su, &bh_su);
+        list_for_each_entry_continue(segbuf, logs, sb_list) {
+                ret = nilfs_sufile_set_segment_usage(sufile, segbuf->sb_segnum,
+                                                     0, 0);
                 WARN_ON(ret); /* always succeed */
-                raw_su->su_nblocks = 0;
-                nilfs_sufile_put_segment_usage(sufile, segbuf->sb_segnum,
-                                               bh_su);
         }
 }
 
@@ -1520,17 +1471,15 @@ static void nilfs_segctor_truncate_segments(struct nilfs_sc_info *sci,
                                             struct nilfs_segment_buffer *last,
                                             struct inode *sufile)
 {
-        struct nilfs_segment_buffer *segbuf = last, *n;
+        struct nilfs_segment_buffer *segbuf = last;
         int ret;
 
-        list_for_each_entry_safe_continue(segbuf, n, &sci->sc_segbufs,
-                                          sb_list) {
-                list_del_init(&segbuf->sb_list);
+        list_for_each_entry_continue(segbuf, &sci->sc_segbufs, sb_list) {
                 sci->sc_segbuf_nblocks -= segbuf->sb_rest_blocks;
                 ret = nilfs_sufile_free(sufile, segbuf->sb_nextnum);
                 WARN_ON(ret);
-                nilfs_segbuf_free(segbuf);
         }
+        nilfs_truncate_logs(&sci->sc_segbufs, last);
 }
 
 
@@ -1562,6 +1511,12 @@ static int nilfs_segctor_collect(struct nilfs_sc_info *sci,
                 if (mode != SC_LSEG_SR || sci->sc_stage.scnt < NILFS_ST_CPFILE)
                         break;
 
+                nilfs_clear_logs(&sci->sc_segbufs);
+
+                err = nilfs_segctor_extend_segments(sci, nilfs, nadd);
+                if (unlikely(err))
+                        return err;
+
                 if (sci->sc_stage.flags & NILFS_CF_SUFREED) {
                         err = nilfs_sufile_cancel_freev(nilfs->ns_sufile,
                                                         sci->sc_freesegs,
@@ -1569,12 +1524,6 @@ static int nilfs_segctor_collect(struct nilfs_sc_info *sci,
                                                         NULL);
                         WARN_ON(err); /* do not happen */
                 }
-                nilfs_segctor_clear_segment_buffers(sci);
-
-                err = nilfs_segctor_extend_segments(sci, nilfs, nadd);
-                if (unlikely(err))
-                        return err;
-
                 nadd = min_t(int, nadd << 1, SC_MAX_SEGDELTA);
                 sci->sc_stage = prev_stage;
         }
@@ -1814,26 +1763,13 @@ static int nilfs_segctor_prepare_write(struct nilfs_sc_info *sci,
 }
 
 static int nilfs_segctor_write(struct nilfs_sc_info *sci,
-                               struct backing_dev_info *bdi)
+                               struct the_nilfs *nilfs)
 {
-        struct nilfs_segment_buffer *segbuf;
-        struct nilfs_write_info wi;
-        int err, res;
-
-        wi.sb = sci->sc_super;
-        wi.bh_sr = sci->sc_super_root;
-        wi.bdi = bdi;
-
-        list_for_each_entry(segbuf, &sci->sc_segbufs, sb_list) {
-                nilfs_segbuf_prepare_write(segbuf, &wi);
-                err = nilfs_segbuf_write(segbuf, &wi);
+        int ret;
 
-                res = nilfs_segbuf_wait(segbuf, &wi);
-                err = err ? : res;
-                if (err)
-                        return err;
-        }
-        return 0;
+        ret = nilfs_write_logs(&sci->sc_segbufs, nilfs);
+        list_splice_tail_init(&sci->sc_segbufs, &sci->sc_write_logs);
+        return ret;
 }
 
 static void __nilfs_end_page_io(struct page *page, int err)
@@ -1911,15 +1847,17 @@ static void nilfs_clear_copied_buffers(struct list_head *list, int err)
         }
 }
 
-static void nilfs_segctor_abort_write(struct nilfs_sc_info *sci,
-                                      struct page *failed_page, int err)
+static void nilfs_abort_logs(struct list_head *logs, struct page *failed_page,
+                             struct buffer_head *bh_sr, int err)
 {
         struct nilfs_segment_buffer *segbuf;
         struct page *bd_page = NULL, *fs_page = NULL;
+        struct buffer_head *bh;
 
-        list_for_each_entry(segbuf, &sci->sc_segbufs, sb_list) {
-                struct buffer_head *bh;
+        if (list_empty(logs))
+                return;
 
+        list_for_each_entry(segbuf, logs, sb_list) {
                 list_for_each_entry(bh, &segbuf->sb_segsum_buffers,
                                     b_assoc_buffers) {
                         if (bh->b_page != bd_page) {
@@ -1931,7 +1869,7 @@ static void nilfs_segctor_abort_write(struct nilfs_sc_info *sci,
 
                 list_for_each_entry(bh, &segbuf->sb_payload_buffers,
                                     b_assoc_buffers) {
-                        if (bh == sci->sc_super_root) {
+                        if (bh == bh_sr) {
                                 if (bh->b_page != bd_page) {
                                         end_page_writeback(bd_page);
                                         bd_page = bh->b_page;
@@ -1941,7 +1879,7 @@ static void nilfs_segctor_abort_write(struct nilfs_sc_info *sci,
                         if (bh->b_page != fs_page) {
                                 nilfs_end_page_io(fs_page, err);
                                 if (fs_page && fs_page == failed_page)
-                                        goto done;
+                                        return;
                                 fs_page = bh->b_page;
                         }
                 }
@@ -1950,8 +1888,33 @@ static void nilfs_segctor_abort_write(struct nilfs_sc_info *sci,
                 end_page_writeback(bd_page);
 
         nilfs_end_page_io(fs_page, err);
- done:
+}
+
+static void nilfs_segctor_abort_construction(struct nilfs_sc_info *sci,
+                                             struct the_nilfs *nilfs, int err)
+{
+        LIST_HEAD(logs);
+        int ret;
+
+        list_splice_tail_init(&sci->sc_write_logs, &logs);
+        ret = nilfs_wait_on_logs(&logs);
+        nilfs_abort_logs(&logs, NULL, sci->sc_super_root, ret ? : err);
+
+        list_splice_tail_init(&sci->sc_segbufs, &logs);
+        nilfs_cancel_segusage(&logs, nilfs->ns_sufile);
+        nilfs_free_incomplete_logs(&logs, nilfs);
         nilfs_clear_copied_buffers(&sci->sc_copied_buffers, err);
+
+        if (sci->sc_stage.flags & NILFS_CF_SUFREED) {
+                ret = nilfs_sufile_cancel_freev(nilfs->ns_sufile,
+                                                sci->sc_freesegs,
+                                                sci->sc_nfreesegs,
+                                                NULL);
+                WARN_ON(ret); /* do not happen */
+        }
+
+        nilfs_destroy_logs(&logs);
+        sci->sc_super_root = NULL;
 }
 
 static void nilfs_set_next_segment(struct the_nilfs *nilfs,
@@ -1969,11 +1932,10 @@ static void nilfs_segctor_complete_write(struct nilfs_sc_info *sci)
 {
         struct nilfs_segment_buffer *segbuf;
         struct page *bd_page = NULL, *fs_page = NULL;
-        struct nilfs_sb_info *sbi = sci->sc_sbi;
-        struct the_nilfs *nilfs = sbi->s_nilfs;
+        struct the_nilfs *nilfs = sci->sc_sbi->s_nilfs;
         int update_sr = (sci->sc_super_root != NULL);
 
-        list_for_each_entry(segbuf, &sci->sc_segbufs, sb_list) {
+        list_for_each_entry(segbuf, &sci->sc_write_logs, sb_list) {
                 struct buffer_head *bh;
 
                 list_for_each_entry(bh, &segbuf->sb_segsum_buffers,
@@ -2046,21 +2008,34 @@ static void nilfs_segctor_complete_write(struct nilfs_sc_info *sci)
 
         sci->sc_nblk_inc += sci->sc_nblk_this_inc;
 
-        segbuf = NILFS_LAST_SEGBUF(&sci->sc_segbufs);
+        segbuf = NILFS_LAST_SEGBUF(&sci->sc_write_logs);
         nilfs_set_next_segment(nilfs, segbuf);
 
         if (update_sr) {
                 nilfs_set_last_segment(nilfs, segbuf->sb_pseg_start,
                                        segbuf->sb_sum.seg_seq, nilfs->ns_cno++);
-                sbi->s_super->s_dirt = 1;
+                set_nilfs_sb_dirty(nilfs);
 
                 clear_bit(NILFS_SC_HAVE_DELTA, &sci->sc_flags);
                 clear_bit(NILFS_SC_DIRTY, &sci->sc_flags);
                 set_bit(NILFS_SC_SUPER_ROOT, &sci->sc_flags);
+                nilfs_segctor_clear_metadata_dirty(sci);
         } else
                 clear_bit(NILFS_SC_SUPER_ROOT, &sci->sc_flags);
 }
 
+static int nilfs_segctor_wait(struct nilfs_sc_info *sci)
+{
+        int ret;
+
+        ret = nilfs_wait_on_logs(&sci->sc_write_logs);
+        if (!ret) {
+                nilfs_segctor_complete_write(sci);
+                nilfs_destroy_logs(&sci->sc_write_logs);
+        }
+        return ret;
+}
+
 static int nilfs_segctor_check_in_files(struct nilfs_sc_info *sci,
                                         struct nilfs_sb_info *sbi)
 {
@@ -2173,7 +2148,7 @@ static int nilfs_segctor_do_construct(struct nilfs_sc_info *sci, int mode)
                 /* Avoid empty segment */
                 if (sci->sc_stage.scnt == NILFS_ST_DONE &&
                     NILFS_SEG_EMPTY(&sci->sc_curseg->sb_sum)) {
-                        nilfs_segctor_end_construction(sci, nilfs, 1);
+                        nilfs_segctor_abort_construction(sci, nilfs, 1);
                         goto out;
                 }
 
@@ -2187,7 +2162,7 @@ static int nilfs_segctor_do_construct(struct nilfs_sc_info *sci, int mode)
                 if (has_sr) {
                         err = nilfs_segctor_fill_in_checkpoint(sci);
                         if (unlikely(err))
-                                goto failed_to_make_up;
+                                goto failed_to_write;
 
                         nilfs_segctor_fill_in_super_root(sci, nilfs);
                 }
@@ -2195,47 +2170,51 @@ static int nilfs_segctor_do_construct(struct nilfs_sc_info *sci, int mode)
 
                 /* Write partial segments */
                 err = nilfs_segctor_prepare_write(sci, &failed_page);
-                if (unlikely(err))
+                if (err) {
+                        nilfs_abort_logs(&sci->sc_segbufs, failed_page,
+                                         sci->sc_super_root, err);
                         goto failed_to_write;
-
+                }
                 nilfs_segctor_fill_in_checksums(sci, nilfs->ns_crc_seed);
 
-                err = nilfs_segctor_write(sci, nilfs->ns_bdi);
+                err = nilfs_segctor_write(sci, nilfs);
                 if (unlikely(err))
                         goto failed_to_write;
 
-                nilfs_segctor_complete_write(sci);
-
-                /* Commit segments */
-                if (has_sr)
-                        nilfs_segctor_clear_metadata_dirty(sci);
-
-                nilfs_segctor_end_construction(sci, nilfs, 0);
-
+                if (sci->sc_stage.scnt == NILFS_ST_DONE ||
+                    nilfs->ns_blocksize_bits != PAGE_CACHE_SHIFT) {
+                        /*
+                         * At this point, we avoid double buffering
+                         * for blocksize < pagesize because page dirty
+                         * flag is turned off during write and dirty
+                         * buffers are not properly collected for
+                         * pages crossing over segments.
+                         */
+                        err = nilfs_segctor_wait(sci);
+                        if (err)
+                                goto failed_to_write;
+                }
         } while (sci->sc_stage.scnt != NILFS_ST_DONE);
 
+        sci->sc_super_root = NULL;
+
  out:
-        nilfs_segctor_destroy_segment_buffers(sci);
         nilfs_segctor_check_out_files(sci, sbi);
         return err;
 
  failed_to_write:
-        nilfs_segctor_abort_write(sci, failed_page, err);
-        nilfs_segctor_cancel_segusage(sci, nilfs->ns_sufile);
-
- failed_to_make_up:
         if (sci->sc_stage.flags & NILFS_CF_IFILE_STARTED)
                 nilfs_redirty_inodes(&sci->sc_dirty_files);
 
  failed:
         if (nilfs_doing_gc())
                 nilfs_redirty_inodes(&sci->sc_gc_inodes);
-        nilfs_segctor_end_construction(sci, nilfs, err);
+        nilfs_segctor_abort_construction(sci, nilfs, err);
         goto out;
 }
 
 /**
- * nilfs_secgtor_start_timer - set timer of background write
+ * nilfs_segctor_start_timer - set timer of background write
  * @sci: nilfs_sc_info
  *
  * If the timer has already been set, it ignores the new request.
@@ -2440,43 +2419,43 @@ int nilfs_construct_dsync_segment(struct super_block *sb, struct inode *inode,
         return err;
 }
 
-struct nilfs_segctor_req {
-        int mode;
-        __u32 seq_accepted;
-        int sc_err;  /* construction failure */
-        int sb_err;  /* super block writeback failure */
-};
-
 #define FLUSH_FILE_BIT  (0x1) /* data file only */
 #define FLUSH_DAT_BIT   (1 << NILFS_DAT_INO) /* DAT only */
 
-static void nilfs_segctor_accept(struct nilfs_sc_info *sci,
-                                 struct nilfs_segctor_req *req)
+/**
+ * nilfs_segctor_accept - record accepted sequence count of log-write requests
+ * @sci: segment constructor object
+ */
+static void nilfs_segctor_accept(struct nilfs_sc_info *sci)
 {
-        req->sc_err = req->sb_err = 0;
         spin_lock(&sci->sc_state_lock);
-        req->seq_accepted = sci->sc_seq_request;
+        sci->sc_seq_accepted = sci->sc_seq_request;
         spin_unlock(&sci->sc_state_lock);
 
         if (sci->sc_timer)
                 del_timer_sync(sci->sc_timer);
 }
 
-static void nilfs_segctor_notify(struct nilfs_sc_info *sci,
-                                 struct nilfs_segctor_req *req)
+/**
+ * nilfs_segctor_notify - notify the result of request to caller threads
+ * @sci: segment constructor object
+ * @mode: mode of log forming
+ * @err: error code to be notified
+ */
+static void nilfs_segctor_notify(struct nilfs_sc_info *sci, int mode, int err)
 {
         /* Clear requests (even when the construction failed) */
         spin_lock(&sci->sc_state_lock);
 
-        if (req->mode == SC_LSEG_SR) {
+        if (mode == SC_LSEG_SR) {
                 sci->sc_state &= ~NILFS_SEGCTOR_COMMIT;
-                sci->sc_seq_done = req->seq_accepted;
-                nilfs_segctor_wakeup(sci, req->sc_err ? : req->sb_err);
+                sci->sc_seq_done = sci->sc_seq_accepted;
+                nilfs_segctor_wakeup(sci, err);
                 sci->sc_flush_request = 0;
         } else {
-                if (req->mode == SC_FLUSH_FILE)
+                if (mode == SC_FLUSH_FILE)
                         sci->sc_flush_request &= ~FLUSH_FILE_BIT;
-                else if (req->mode == SC_FLUSH_DAT)
+                else if (mode == SC_FLUSH_DAT)
                         sci->sc_flush_request &= ~FLUSH_DAT_BIT;
 
                 /* re-enable timer if checkpoint creation was not done */
@@ -2487,30 +2466,37 @@ static void nilfs_segctor_notify(struct nilfs_sc_info *sci,
         spin_unlock(&sci->sc_state_lock);
 }
 
-static int nilfs_segctor_construct(struct nilfs_sc_info *sci,
-                                   struct nilfs_segctor_req *req)
+/**
+ * nilfs_segctor_construct - form logs and write them to disk
+ * @sci: segment constructor object
+ * @mode: mode of log forming
+ */
+static int nilfs_segctor_construct(struct nilfs_sc_info *sci, int mode)
 {
         struct nilfs_sb_info *sbi = sci->sc_sbi;
         struct the_nilfs *nilfs = sbi->s_nilfs;
         int err = 0;
 
+        nilfs_segctor_accept(sci);
+
         if (nilfs_discontinued(nilfs))
-                req->mode = SC_LSEG_SR;
-        if (!nilfs_segctor_confirm(sci)) {
-                err = nilfs_segctor_do_construct(sci, req->mode);
-                req->sc_err = err;
-        }
+                mode = SC_LSEG_SR;
+        if (!nilfs_segctor_confirm(sci))
+                err = nilfs_segctor_do_construct(sci, mode);
+
         if (likely(!err)) {
-                if (req->mode != SC_FLUSH_DAT)
+                if (mode != SC_FLUSH_DAT)
                         atomic_set(&nilfs->ns_ndirtyblks, 0);
                 if (test_bit(NILFS_SC_SUPER_ROOT, &sci->sc_flags) &&
                     nilfs_discontinued(nilfs)) {
                         down_write(&nilfs->ns_sem);
-                        req->sb_err = nilfs_commit_super(sbi,
-                                        nilfs_altsb_need_update(nilfs));
+                        err = nilfs_commit_super(
+                                sbi, nilfs_altsb_need_update(nilfs));
                         up_write(&nilfs->ns_sem);
                 }
         }
+
+        nilfs_segctor_notify(sci, mode, err);
         return err;
 }
 
@@ -2541,7 +2527,6 @@ int nilfs_clean_segments(struct super_block *sb, struct nilfs_argv *argv,
         struct nilfs_sc_info *sci = NILFS_SC(sbi);
         struct the_nilfs *nilfs = sbi->s_nilfs;
         struct nilfs_transaction_info ti;
-        struct nilfs_segctor_req req = { .mode = SC_LSEG_SR };
         int err;
 
         if (unlikely(!sci))
@@ -2559,13 +2544,11 @@ int nilfs_clean_segments(struct super_block *sb, struct nilfs_argv *argv,
 
         sci->sc_freesegs = kbufs[4];
         sci->sc_nfreesegs = argv[4].v_nmembs;
-        list_splice_init(&nilfs->ns_gc_inodes, sci->sc_gc_inodes.prev);
+        list_splice_tail_init(&nilfs->ns_gc_inodes, &sci->sc_gc_inodes);
 
         for (;;) {
-                nilfs_segctor_accept(sci, &req);
-                err = nilfs_segctor_construct(sci, &req);
+                err = nilfs_segctor_construct(sci, SC_LSEG_SR);
                 nilfs_remove_written_gcinodes(nilfs, &sci->sc_gc_inodes);
-                nilfs_segctor_notify(sci, &req);
 
                 if (likely(!err))
                         break;
@@ -2575,6 +2558,16 @@ int nilfs_clean_segments(struct super_block *sb, struct nilfs_argv *argv,
                 set_current_state(TASK_INTERRUPTIBLE);
                 schedule_timeout(sci->sc_interval);
         }
+        if (nilfs_test_opt(sbi, DISCARD)) {
+                int ret = nilfs_discard_segments(nilfs, sci->sc_freesegs,
+                                                 sci->sc_nfreesegs);
+                if (ret) {
+                        printk(KERN_WARNING
+                               "NILFS warning: error %d on discard request, "
+                               "turning discards off for the device\n", ret);
+                        nilfs_clear_opt(sbi, DISCARD);
+                }
+        }
 
  out_unlock:
         sci->sc_freesegs = NULL;
@@ -2588,13 +2581,9 @@ static void nilfs_segctor_thread_construct(struct nilfs_sc_info *sci, int mode)
 {
         struct nilfs_sb_info *sbi = sci->sc_sbi;
         struct nilfs_transaction_info ti;
-        struct nilfs_segctor_req req = { .mode = mode };
 
         nilfs_transaction_lock(sbi, &ti, 0);
-
-        nilfs_segctor_accept(sci, &req);
-        nilfs_segctor_construct(sci, &req);
-        nilfs_segctor_notify(sci, &req);
+        nilfs_segctor_construct(sci, mode);
 
         /*
          * Unclosed segment should be retried.  We do this using sc_timer.
@@ -2650,6 +2639,7 @@ static int nilfs_segctor_flush_mode(struct nilfs_sc_info *sci)
 static int nilfs_segctor_thread(void *arg)
 {
         struct nilfs_sc_info *sci = (struct nilfs_sc_info *)arg;
+        struct the_nilfs *nilfs = sci->sc_sbi->s_nilfs;
         struct timer_list timer;
         int timeout = 0;
 
@@ -2695,7 +2685,6 @@ static int nilfs_segctor_thread(void *arg)
         } else {
                 DEFINE_WAIT(wait);
                 int should_sleep = 1;
-                struct the_nilfs *nilfs;
 
                 prepare_to_wait(&sci->sc_wait_daemon, &wait,
                                 TASK_INTERRUPTIBLE);
@@ -2716,8 +2705,8 @@ static int nilfs_segctor_thread(void *arg)
                 finish_wait(&sci->sc_wait_daemon, &wait);
                 timeout = ((sci->sc_state & NILFS_SEGCTOR_COMMIT) &&
                            time_after_eq(jiffies, sci->sc_timer->expires));
-                nilfs = sci->sc_sbi->s_nilfs;
-                if (sci->sc_super->s_dirt && nilfs_sb_need_update(nilfs))
+
+                if (nilfs_sb_dirty(nilfs) && nilfs_sb_need_update(nilfs))
                         set_nilfs_discontinued(nilfs);
         }
         goto loop;
@@ -2788,6 +2777,7 @@ static struct nilfs_sc_info *nilfs_segctor_new(struct nilfs_sb_info *sbi)
         spin_lock_init(&sci->sc_state_lock);
         INIT_LIST_HEAD(&sci->sc_dirty_files);
         INIT_LIST_HEAD(&sci->sc_segbufs);
+        INIT_LIST_HEAD(&sci->sc_write_logs);
         INIT_LIST_HEAD(&sci->sc_gc_inodes);
         INIT_LIST_HEAD(&sci->sc_copied_buffers);
 
@@ -2811,12 +2801,9 @@ static void nilfs_segctor_write_out(struct nilfs_sc_info *sci)
         do {
                 struct nilfs_sb_info *sbi = sci->sc_sbi;
                 struct nilfs_transaction_info ti;
-                struct nilfs_segctor_req req = { .mode = SC_LSEG_SR };
 
                 nilfs_transaction_lock(sbi, &ti, 0);
-                nilfs_segctor_accept(sci, &req);
-                ret = nilfs_segctor_construct(sci, &req);
-                nilfs_segctor_notify(sci, &req);
+                ret = nilfs_segctor_construct(sci, SC_LSEG_SR);
                 nilfs_transaction_unlock(sbi);
 
         } while (ret && retrycount-- > 0);
@@ -2843,7 +2830,7 @@ static void nilfs_segctor_destroy(struct nilfs_sc_info *sci)
                 || sci->sc_seq_request != sci->sc_seq_done);
         spin_unlock(&sci->sc_state_lock);
 
-        if (flag || nilfs_segctor_confirm(sci))
+        if (flag || !nilfs_segctor_confirm(sci))
                 nilfs_segctor_write_out(sci);
 
         WARN_ON(!list_empty(&sci->sc_copied_buffers));
@@ -2855,6 +2842,7 @@ static void nilfs_segctor_destroy(struct nilfs_sc_info *sci)
         }
 
         WARN_ON(!list_empty(&sci->sc_segbufs));
+        WARN_ON(!list_empty(&sci->sc_write_logs));
 
         down_write(&sbi->s_nilfs->ns_segctor_sem);
 
@@ -2866,7 +2854,7 @@ static void nilfs_segctor_destroy(struct nilfs_sc_info *sci)
  * @sbi: nilfs_sb_info
  *
  * nilfs_attach_segment_constructor() allocates a struct nilfs_sc_info,
- * initilizes it, and starts the segment constructor.
+ * initializes it, and starts the segment constructor.
  *
  * Return Value: On success, 0 is returned. On error, one of the following
  * negative error code is returned.
@@ -2878,8 +2866,15 @@ int nilfs_attach_segment_constructor(struct nilfs_sb_info *sbi)
         struct the_nilfs *nilfs = sbi->s_nilfs;
         int err;
 
-        /* Each field of nilfs_segctor is cleared through the initialization
-           of super-block info */
+        if (NILFS_SC(sbi)) {
+                /*
+                 * This happens if the filesystem was remounted
+                 * read/write after nilfs_error degenerated it into a
+                 * read-only mount.
+                 */
+                nilfs_detach_segment_constructor(sbi);
+        }
+
         sbi->s_sc_info = nilfs_segctor_new(sbi);
         if (!sbi->s_sc_info)
                 return -ENOMEM;