ext4: Retry block allocation if we have free blocks left

When we truncate files, the meta-data blocks released are not reused
untill we commit the truncate transaction.  That means delayed get_block
request will return ENOSPC even if we have free blocks left.  Force a
journal commit and retry block allocation if we get ENOSPC with free
blocks left.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Mingming Cao <cmm@us.ibm.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

1 files changed, 57 insertions, 24 deletions

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index b567e71f5be9..f97b3478eb89 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -1634,6 +1634,7 @@ struct mpage_da_data {
         struct writeback_control *wbc;
         int io_done;
         long pages_written;
+        int retval;
 };
 
 /*
@@ -1820,6 +1821,24 @@ static void ext4_da_block_invalidatepages(struct mpage_da_data *mpd,
         return;
 }
 
+static void ext4_print_free_blocks(struct inode *inode)
+{
+        struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
+        printk(KERN_EMERG "Total free blocks count %lld\n",
+                        ext4_count_free_blocks(inode->i_sb));
+        printk(KERN_EMERG "Free/Dirty block details\n");
+        printk(KERN_EMERG "free_blocks=%lld\n",
+                        percpu_counter_sum(&sbi->s_freeblocks_counter));
+        printk(KERN_EMERG "dirty_blocks=%lld\n",
+                        percpu_counter_sum(&sbi->s_dirtyblocks_counter));
+        printk(KERN_EMERG "Block reservation details\n");
+        printk(KERN_EMERG "i_reserved_data_blocks=%lu\n",
+                        EXT4_I(inode)->i_reserved_data_blocks);
+        printk(KERN_EMERG "i_reserved_meta_blocks=%lu\n",
+                        EXT4_I(inode)->i_reserved_meta_blocks);
+        return;
+}
+
 /*
  * mpage_da_map_blocks - go through given space
  *
@@ -1834,7 +1853,7 @@ static int  mpage_da_map_blocks(struct mpage_da_data *mpd)
         int err = 0;
         struct buffer_head new;
         struct buffer_head *lbh = &mpd->lbh;
-        sector_t next = lbh->b_blocknr;
+        sector_t next;
 
         /*
          * We consider only non-mapped and non-allocated blocks
@@ -1844,6 +1863,7 @@ static int  mpage_da_map_blocks(struct mpage_da_data *mpd)
         new.b_state = lbh->b_state;
         new.b_blocknr = 0;
         new.b_size = lbh->b_size;
+        next = lbh->b_blocknr;
         /*
          * If we didn't accumulate anything
          * to write simply return
@@ -1860,6 +1880,13 @@ static int  mpage_da_map_blocks(struct mpage_da_data *mpd)
                  */
                 if (err == -EAGAIN)
                         return 0;
+
+                if (err == -ENOSPC &&
+                                ext4_count_free_blocks(mpd->inode->i_sb)) {
+                        mpd->retval = err;
+                        return 0;
+                }
+
                 /*
                  * get block failure will cause us
                  * to loop in writepages. Because
@@ -1877,8 +1904,7 @@ static int  mpage_da_map_blocks(struct mpage_da_data *mpd)
                 printk(KERN_EMERG "This should not happen.!! "
                                         "Data will be lost\n");
                 if (err == -ENOSPC) {
-                        printk(KERN_CRIT "Total free blocks count %lld\n",
-                                ext4_count_free_blocks(mpd->inode->i_sb));
+                        ext4_print_free_blocks(mpd->inode);
                 }
                 /* invlaidate all the pages */
                 ext4_da_block_invalidatepages(mpd, next,
@@ -2085,39 +2111,36 @@ static int __mpage_da_writepage(struct page *page,
  */
 static int mpage_da_writepages(struct address_space *mapping,
                                struct writeback_control *wbc,
-                               get_block_t get_block)
+                               struct mpage_da_data *mpd)
 {
-        struct mpage_da_data mpd;
         long to_write;
         int ret;
 
-        if (!get_block)
+        if (!mpd->get_block)
                 return generic_writepages(mapping, wbc);
 
-        mpd.wbc = wbc;
-        mpd.inode = mapping->host;
-        mpd.lbh.b_size = 0;
-        mpd.lbh.b_state = 0;
-        mpd.lbh.b_blocknr = 0;
-        mpd.first_page = 0;
-        mpd.next_page = 0;
-        mpd.get_block = get_block;
-        mpd.io_done = 0;
-        mpd.pages_written = 0;
+        mpd->lbh.b_size = 0;
+        mpd->lbh.b_state = 0;
+        mpd->lbh.b_blocknr = 0;
+        mpd->first_page = 0;
+        mpd->next_page = 0;
+        mpd->io_done = 0;
+        mpd->pages_written = 0;
+        mpd->retval = 0;
 
         to_write = wbc->nr_to_write;
 
-        ret = write_cache_pages(mapping, wbc, __mpage_da_writepage, &mpd);
+        ret = write_cache_pages(mapping, wbc, __mpage_da_writepage, mpd);
 
         /*
          * Handle last extent of pages
          */
-        if (!mpd.io_done && mpd.next_page != mpd.first_page) {
-                if (mpage_da_map_blocks(&mpd) == 0)
-                        mpage_da_submit_io(&mpd);
+        if (!mpd->io_done && mpd->next_page != mpd->first_page) {
+                if (mpage_da_map_blocks(mpd) == 0)
+                        mpage_da_submit_io(mpd);
         }
 
-        wbc->nr_to_write = to_write - mpd.pages_written;
+        wbc->nr_to_write = to_write - mpd->pages_written;
         return ret;
 }
 
@@ -2357,6 +2380,7 @@ static int ext4_da_writepages(struct address_space *mapping,
 {
         handle_t *handle = NULL;
         loff_t range_start = 0;
+        struct mpage_da_data mpd;
         struct inode *inode = mapping->host;
         int needed_blocks, ret = 0, nr_to_writebump = 0;
         long to_write, pages_skipped = 0;
@@ -2390,6 +2414,9 @@ static int ext4_da_writepages(struct address_space *mapping,
         range_start =  wbc->range_start;
         pages_skipped = wbc->pages_skipped;
 
+        mpd.wbc = wbc;
+        mpd.inode = mapping->host;
+
 restart_loop:
         to_write = wbc->nr_to_write;
         while (!ret && to_write > 0) {
@@ -2413,11 +2440,17 @@ restart_loop:
                         dump_stack();
                         goto out_writepages;
                 }
-
                 to_write -= wbc->nr_to_write;
-                ret = mpage_da_writepages(mapping, wbc,
-                                          ext4_da_get_block_write);
+
+                mpd.get_block = ext4_da_get_block_write;
+                ret = mpage_da_writepages(mapping, wbc, &mpd);
+
                 ext4_journal_stop(handle);
+
+                if (mpd.retval == -ENOSPC)
+                        jbd2_journal_force_commit_nested(sbi->s_journal);
+
+                /* reset the retry count */
                 if (ret == MPAGE_DA_EXTENT_TAIL) {
                         /*
                          * got one extent now try with