UBIFS: pre-allocate bulk-read buffer

To avoid memory allocation failure during bulk-read, pre-allocate
a bulk-read buffer, so that if there is only one bulk-reader at
a time, it would just use the pre-allocated buffer and would not
do any memory allocation. However, if there are more than 1 bulk-
reader, then only one reader would use the pre-allocated buffer,
while the other reader would allocate the buffer for itself.

Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>

3 files changed, 76 insertions, 18 deletions

diff --git a/fs/ubifs/file.c b/fs/ubifs/file.c
index 0c5c27d63f6e..2624411d9758 100644
--- a/fs/ubifs/file.c
+++ b/fs/ubifs/file.c
@@ -811,15 +811,15 @@ static int ubifs_bulk_read(struct page *page)
         struct ubifs_inode *ui = ubifs_inode(inode);
         pgoff_t index = page->index, last_page_read = ui->last_page_read;
         struct bu_info *bu;
-        int err = 0;
+        int err = 0, allocated = 0;
 
         ui->last_page_read = index;
         if (!c->bulk_read)
                 return 0;
 
         /*
-         * Bulk-read is protected by ui_mutex, but it is an optimization, so
-         * don't bother if we cannot lock the mutex.
+         * Bulk-read is protected by @ui->ui_mutex, but it is an optimization,
+         * so don't bother if we cannot lock the mutex.
          */
         if (!mutex_trylock(&ui->ui_mutex))
                 return 0;
@@ -840,17 +840,30 @@ static int ubifs_bulk_read(struct page *page)
                 ui->bulk_read = 1;
         }
 
-        bu = kmalloc(sizeof(struct bu_info), GFP_NOFS | __GFP_NOWARN);
-        if (!bu)
-                return 0;
+        /*
+         * If possible, try to use pre-allocated bulk-read information, which
+         * is protected by @c->bu_mutex.
+         */
+        if (mutex_trylock(&c->bu_mutex))
+                bu = &c->bu;
+        else {
+                bu = kmalloc(sizeof(struct bu_info), GFP_NOFS | __GFP_NOWARN);
+                if (!bu)
+                        goto out_unlock;
+
+                bu->buf = NULL;
+                allocated = 1;
+        }
 
-        bu->buf = NULL;
         bu->buf_len = c->max_bu_buf_len;
         data_key_init(c, &bu->key, inode->i_ino,
                       page->index << UBIFS_BLOCKS_PER_PAGE_SHIFT);
-
         err = ubifs_do_bulk_read(c, bu, page);
-        kfree(bu);
+
+        if (!allocated)
+                mutex_unlock(&c->bu_mutex);
+        else
+                kfree(bu);
 
 out_unlock:
         mutex_unlock(&ui->ui_mutex);
diff --git a/fs/ubifs/super.c b/fs/ubifs/super.c
index 1d511569c035..d80b2aef42b6 100644
--- a/fs/ubifs/super.c
+++ b/fs/ubifs/super.c
@@ -572,14 +572,6 @@ static int init_constants_early(struct ubifs_info *c)
         c->max_bu_buf_len = UBIFS_MAX_BULK_READ * UBIFS_MAX_DATA_NODE_SZ;
         if (c->max_bu_buf_len > c->leb_size)
                 c->max_bu_buf_len = c->leb_size;
-        if (c->max_bu_buf_len > UBIFS_KMALLOC_OK) {
-                /* Check if we can kmalloc that much */
-                void *try = kmalloc(c->max_bu_buf_len,
-                                    GFP_KERNEL | __GFP_NOWARN);
-                kfree(try);
-                if (!try)
-                        c->max_bu_buf_len = UBIFS_KMALLOC_OK;
-        }
         return 0;
 }
 
@@ -999,6 +991,34 @@ static void destroy_journal(struct ubifs_info *c)
 }
 
 /**
+ * bu_init - initialize bulk-read information.
+ * @c: UBIFS file-system description object
+ */
+static void bu_init(struct ubifs_info *c)
+{
+        ubifs_assert(c->bulk_read == 1);
+
+        if (c->bu.buf)
+                return; /* Already initialized */
+
+again:
+        c->bu.buf = kmalloc(c->max_bu_buf_len, GFP_KERNEL | __GFP_NOWARN);
+        if (!c->bu.buf) {
+                if (c->max_bu_buf_len > UBIFS_KMALLOC_OK) {
+                        c->max_bu_buf_len = UBIFS_KMALLOC_OK;
+                        goto again;
+                }
+
+                /* Just disable bulk-read */
+                ubifs_warn("Cannot allocate %d bytes of memory for bulk-read, "
+                           "disabling it", c->max_bu_buf_len);
+                c->mount_opts.bulk_read = 1;
+                c->bulk_read = 0;
+                return;
+        }
+}
+
+/**
  * mount_ubifs - mount UBIFS file-system.
  * @c: UBIFS file-system description object
  *
@@ -1066,6 +1086,13 @@ static int mount_ubifs(struct ubifs_info *c)
                         goto out_free;
         }
 
+        if (c->bulk_read == 1)
+                bu_init(c);
+
+        /*
+         * We have to check all CRCs, even for data nodes, when we mount the FS
+         * (specifically, when we are replaying).
+         */
         c->always_chk_crc = 1;
 
         err = ubifs_read_superblock(c);
@@ -1296,6 +1323,7 @@ out_cbuf:
 out_dereg:
         dbg_failure_mode_deregistration(c);
 out_free:
+        kfree(c->bu.buf);
         vfree(c->ileb_buf);
         vfree(c->sbuf);
         kfree(c->bottom_up_buf);
@@ -1332,10 +1360,11 @@ static void ubifs_umount(struct ubifs_info *c)
         kfree(c->cbuf);
         kfree(c->rcvrd_mst_node);
         kfree(c->mst_node);
+        kfree(c->bu.buf);
+        vfree(c->ileb_buf);
         vfree(c->sbuf);
         kfree(c->bottom_up_buf);
         UBIFS_DBG(vfree(c->dbg_buf));
-        vfree(c->ileb_buf);
         dbg_failure_mode_deregistration(c);
 }
 
@@ -1633,6 +1662,7 @@ static int ubifs_remount_fs(struct super_block *sb, int *flags, char *data)
                 ubifs_err("invalid or unknown remount parameter");
                 return err;
         }
+
         if ((sb->s_flags & MS_RDONLY) && !(*flags & MS_RDONLY)) {
                 err = ubifs_remount_rw(c);
                 if (err)
@@ -1640,6 +1670,14 @@ static int ubifs_remount_fs(struct super_block *sb, int *flags, char *data)
         } else if (!(sb->s_flags & MS_RDONLY) && (*flags & MS_RDONLY))
                 ubifs_remount_ro(c);
 
+        if (c->bulk_read == 1)
+                bu_init(c);
+        else {
+                dbg_gen("disable bulk-read");
+                kfree(c->bu.buf);
+                c->bu.buf = NULL;
+        }
+
         return 0;
 }
 
@@ -1730,6 +1768,7 @@ static int ubifs_fill_super(struct super_block *sb, void *data, int silent)
         mutex_init(&c->log_mutex);
         mutex_init(&c->mst_mutex);
         mutex_init(&c->umount_mutex);
+        mutex_init(&c->bu_mutex);
         init_waitqueue_head(&c->cmt_wq);
         c->buds = RB_ROOT;
         c->old_idx = RB_ROOT;
diff --git a/fs/ubifs/ubifs.h b/fs/ubifs/ubifs.h
index 870b5c479e95..46b172560a06 100644
--- a/fs/ubifs/ubifs.h
+++ b/fs/ubifs/ubifs.h
@@ -969,7 +969,10 @@ struct ubifs_mount_opts {
  * @mst_node: master node
  * @mst_offs: offset of valid master node
  * @mst_mutex: protects the master node area, @mst_node, and @mst_offs
+ *
  * @max_bu_buf_len: maximum bulk-read buffer length
+ * @bu_mutex: protects the pre-allocated bulk-read buffer and @c->bu
+ * @bu: pre-allocated bulk-read information
  *
  * @log_lebs: number of logical eraseblocks in the log
  * @log_bytes: log size in bytes
@@ -1217,7 +1220,10 @@ struct ubifs_info {
         struct ubifs_mst_node *mst_node;
         int mst_offs;
         struct mutex mst_mutex;
+
         int max_bu_buf_len;
+        struct mutex bu_mutex;
+        struct bu_info bu;
 
         int log_lebs;
         long long log_bytes;