handling unwritten extents lookup/map/convert for direct IO request.
For already fallocated extent, at the time DIO get_block() is called,
ext4 will split the fallocated extent as necessary, mark the to-write
fallocated extent mapped but still remains unwritten. Need to insert the
splitted extents, to prevent ENOSPC later.
At the time all IO has completed, end_io call back function will mark
the unwritten extent as written.
Patch against ext4 patch queue.
Comments?
Singed-Off-By: Mingming Cao <cmm@xxxxxxxxxx>
---
fs/ext4/ext4_extents.h | 5
fs/ext4/extents.c | 401 +++++++++++++++++++++++++++++++++++++++++++++----
2 files changed, 377 insertions(+), 29 deletions(-)
Index: linux-2.6.31-rc4/fs/ext4/ext4_extents.h
===================================================================
--- linux-2.6.31-rc4.orig/fs/ext4/ext4_extents.h 2009-08-09 14:53:08.000000000 -0700
+++ linux-2.6.31-rc4/fs/ext4/ext4_extents.h 2009-08-09 14:53:27.000000000 -0700
@@ -220,6 +220,11 @@ static inline int ext4_ext_get_actual_le
(le16_to_cpu(ext->ee_len) - EXT_INIT_MAX_LEN));
}
+static inline void ext4_ext_mark_initialized(struct ext4_extent *ext)
+{
+ ext->ee_len = ext4_ext_get_actual_len(ext);
+}
+
extern int ext4_ext_calc_metadata_amount(struct inode *inode, int blocks);
extern ext4_fsblk_t ext_pblock(struct ext4_extent *ex);
extern ext4_fsblk_t idx_pblock(struct ext4_extent_idx *);
Index: linux-2.6.31-rc4/fs/ext4/extents.c
===================================================================
--- linux-2.6.31-rc4.orig/fs/ext4/extents.c 2009-08-09 14:53:01.000000000 -0700
+++ linux-2.6.31-rc4/fs/ext4/extents.c 2009-08-09 14:53:19.000000000 -0700
@@ -2461,7 +2461,6 @@ static int ext4_ext_zeroout(struct inode
}
#define EXT4_EXT_ZERO_LEN 7
-
/*
* This function is called by ext4_ext_get_blocks() if someone tries to write
* to an uninitialized extent. It may result in splitting the uninitialized
@@ -2755,6 +2754,303 @@ fix_extent_len:
}
/*
+ * This function is called by ext4_ext_get_blocks() from
+ * ext4_get_blocks_dio_write() when DIO to write
+ * to an uninitialized extent.
+ *
+ * Writing to an uninitized extent may result in splitting the uninitialized
+ * extent into multiple /intialized unintialized extents (up to three)
+ * There are three possibilities:
+ * a> There is no split required: Entire extent should be uninitialized
+ * b> Splits in two extents: Write is happening at either end of the extent
+ * c> Splits in three extents: Somone is writing in middle of the extent
+ *
+ * One of more index blocks maybe needed if the extent tree grow after
+ * the unintialized extent split. To prevent ENOSPC occur at the IO
+ * complete, we need to split the uninitialized extent before DIO submit
+ * the IO. The uninitilized extent called at this time will be split
+ * into three uninitialized extent(at most). After IO complete, the part
+ * being filled will be convert to initialized by the end_io callback function
+ * via ext4_convert_unwritten_extents().
+ */
+static int ext4_split_unwritten_extents(handle_t *handle,
+ struct inode *inode,
+ struct ext4_ext_path *path,
+ ext4_lblk_t iblock,
+ unsigned int max_blocks)
+{
+ struct ext4_extent *ex, newex, orig_ex;
+ struct ext4_extent *ex1 = NULL;
+ struct ext4_extent *ex2 = NULL;
+ struct ext4_extent *ex3 = NULL;
+ struct ext4_extent_header *eh;
+ ext4_lblk_t ee_block;
+ unsigned int allocated, ee_len, depth;
+ ext4_fsblk_t newblock;
+ int err = 0;
+ int ret = 0;
+
+ depth = ext_depth(inode);
+ eh = path[depth].p_hdr;
+ ex = path[depth].p_ext;
+ ee_block = le32_to_cpu(ex->ee_block);
+ ee_len = ext4_ext_get_actual_len(ex);
+ allocated = ee_len - (iblock - ee_block);
+ newblock = iblock - ee_block + ext_pblock(ex);
+ ex2 = ex;
+ orig_ex.ee_block = ex->ee_block;
+ orig_ex.ee_len = cpu_to_le16(ee_len);
+ ext4_ext_store_pblock(&orig_ex, ext_pblock(ex));
+
+ /*
+ * if the entire unintialized extent length less than
+ * the size of extent to write, there is no need to split
+ * uninitialized extent
+ */
+ if (allocated <= max_blocks)
+ return ret;
+
+ err = ext4_ext_get_access(handle, inode, path + depth);
+ if (err)
+ goto out;
+ /* ex1: ee_block to iblock - 1 : uninitialized */
+ if (iblock > ee_block) {
+ ex1 = ex;
+ ex1->ee_len = cpu_to_le16(iblock - ee_block);
+ ext4_ext_mark_uninitialized(ex1);
+ ex2 = &newex;
+ }
+ /*
+ * for sanity, update the length of the ex2 extent before
+ * we insert ex3, if ex1 is NULL. This is to avoid temporary
+ * overlap of blocks.
+ */
+ if (!ex1 && allocated > max_blocks)
+ ex2->ee_len = cpu_to_le16(max_blocks);
+ /* ex3: to ee_block + ee_len : uninitialised */
+ if (allocated > max_blocks) {
+ unsigned int newdepth;
+ ex3 = &newex;
+ ex3->ee_block = cpu_to_le32(iblock + max_blocks);
+ ext4_ext_store_pblock(ex3, newblock + max_blocks);
+ ex3->ee_len = cpu_to_le16(allocated - max_blocks);
+ ext4_ext_mark_uninitialized(ex3);
+ err = ext4_ext_insert_extent(handle, inode, path, ex3);
+ if (err == -ENOSPC) {
+ err = ext4_ext_zeroout(inode, &orig_ex);
+ if (err)
+ goto fix_extent_len;
+ /* update the extent length and mark as initialized */
+ ex->ee_block = orig_ex.ee_block;
+ ex->ee_len = orig_ex.ee_len;
+ ext4_ext_store_pblock(ex, ext_pblock(&orig_ex));
+ ext4_ext_dirty(handle, inode, path + depth);
+ /* zeroed the full extent */
+ /* blocks available from iblock */
+ return allocated;
+
+ } else if (err)
+ goto fix_extent_len;
+ /*
+ * The depth, and hence eh & ex might change
+ * as part of the insert above.
+ */
+ newdepth = ext_depth(inode);
+ /*
+ * update the extent length after successful insert of the
+ * split extent
+ */
+ orig_ex.ee_len = cpu_to_le16(ee_len -
+ ext4_ext_get_actual_len(ex3));
+ depth = newdepth;
+ ext4_ext_drop_refs(path);
+ path = ext4_ext_find_extent(inode, iblock, path);
+ if (IS_ERR(path)) {
+ err = PTR_ERR(path);
+ goto out;
+ }
+ eh = path[depth].p_hdr;
+ ex = path[depth].p_ext;
+ if (ex2 != &newex)
+ ex2 = ex;
+
+ err = ext4_ext_get_access(handle, inode, path + depth);
+ if (err)
+ goto out;
+
+ allocated = max_blocks;
+ }
+ /*
+ * If there was a change of depth as part of the
+ * insertion of ex3 above, we need to update the length
+ * of the ex1 extent again here
+ */
+ if (ex1 && ex1 != ex) {
+ ex1 = ex;
+ ex1->ee_len = cpu_to_le16(iblock - ee_block);
+ ext4_ext_mark_uninitialized(ex1);
+ ex2 = &newex;
+ }
+ /* ex2: iblock to iblock + maxblocks-1 : initialised */
+ ex2->ee_block = cpu_to_le32(iblock);
+ ext4_ext_store_pblock(ex2, newblock);
+ ex2->ee_len = cpu_to_le16(allocated);
+ ext4_ext_mark_uninitialized(ex2);
+ if (ex2 != ex)
+ goto insert;
+ /* Mark modified extent as dirty */
+ err = ext4_ext_dirty(handle, inode, path + depth);
+ goto out;
+insert:
+ err = ext4_ext_insert_extent(handle, inode, path, &newex);
+ if (err == -ENOSPC) {
+ err = ext4_ext_zeroout(inode, &orig_ex);
+ if (err)
+ goto fix_extent_len;
+ /* update the extent length and mark as initialized */
+ ex->ee_block = orig_ex.ee_block;
+ ex->ee_len = orig_ex.ee_len;
+ ext4_ext_store_pblock(ex, ext_pblock(&orig_ex));
+ ext4_ext_dirty(handle, inode, path + depth);
+ /* zero out the first half */
+ return allocated;
+ } else if (err)
+ goto fix_extent_len;
+out:
+ return err ? err : allocated;
+
+fix_extent_len:
+ ex->ee_block = orig_ex.ee_block;
+ ex->ee_len = orig_ex.ee_len;
+ ext4_ext_store_pblock(ex, ext_pblock(&orig_ex));
+ ext4_ext_mark_uninitialized(ex);
+ ext4_ext_dirty(handle, inode, path + depth);
+ return err;
+}
+static int ext4_convert_unwritten_extents_dio(handle_t *handle,
+ struct inode *inode,
+ struct ext4_ext_path *path)
+{
+ struct ext4_extent *ex;
+ struct ext4_extent_header *eh;
+ int depth;
+ int err = 0;
+ int ret = 0;
+
+ depth = ext_depth(inode);
+ eh = path[depth].p_hdr;
+ ex = path[depth].p_ext;
+
+ /* first mark the extent as initialized */
+ ext4_ext_mark_initialized(ex);
+
+ if (err < 0)
+ return err;
+ /*
+ * We have to see if it can be merged with the extent
+ * on the left.
+ */
+ if (ex > EXT_FIRST_EXTENT(eh)) {
+ /*
+ * To merge left, pass "ex - 1" to try_to_merge(),
+ * since it merges towards right _only_.
+ */
+ ret = ext4_ext_try_to_merge(inode, path, ex - 1);
+ if (ret) {
+ err = ext4_ext_correct_indexes(handle, inode, path);
+ if (err)
+ goto out;
+ depth = ext_depth(inode);
+ ex--;
+ }
+ }
+ /*
+ * Try to Merge towards right.
+ */
+ ret = ext4_ext_try_to_merge(inode, path, ex);
+ if (ret) {
+ err = ext4_ext_correct_indexes(handle, inode, path);
+ if (err)
+ goto out;
+ depth = ext_depth(inode);
+ }
+ /* Mark modified extent as dirty */
+ err = ext4_ext_dirty(handle, inode, path + depth);
+out:
+ return err;
+}
+
+static int
+ext4_ext_handle_uninitialized_extents(handle_t *handle, struct inode *inode,
+ ext4_lblk_t iblock, unsigned int max_blocks,
+ struct ext4_ext_path *path, int flags,
+ unsigned int allocated, struct buffer_head *bh_result,
+ ext4_fsblk_t newblock)
+{
+ int ret = 0;
+ int err = 0;
+
+ /* DIO get_block() before submit the IO, split the extent */
+ if (flags == EXT4_GET_BLOCKS_DIO_CREATE_EXT) {
+ ret = ext4_split_unwritten_extents(handle,
+ inode, path, iblock,
+ max_blocks);
+ goto out;
+ }
+ /* DIO end_io complete, convert the filled extent to written */
+ if (flags == EXT4_GET_BLOCKS_DIO_CONVERT_EXT) {
+ ret = ext4_convert_unwritten_extents_dio(handle, inode,
+ path);
+ goto out2;
+ }
+ /* buffered IO case */
+ /*
+ * repeat fallocate creation request
+ * we already have an unwritten extent
+ */
+ if (flags & EXT4_GET_BLOCKS_UNINIT_EXT)
+ goto map_out;
+
+ /* buffered READ or buffered write_begin() lookup */
+ if ((flags & EXT4_GET_BLOCKS_CREATE) == 0) {
+ /*
+ * We have blocks reserved already. We
+ * return allocated blocks so that delalloc
+ * won't do block reservation for us. But
+ * the buffer head will be unmapped so that
+ * a read from the block returns 0s.
+ */
+ set_buffer_unwritten(bh_result);
+ goto out1;
+ }
+
+ /* buffered write, writepage time, convert*/
+ ret = ext4_ext_convert_to_initialized(handle, inode,
+ path, iblock,
+ max_blocks);
+out:
+ if (ret <= 0) {
+ err = ret;
+ goto out2;
+ } else
+ allocated = ret;
+ set_buffer_new(bh_result);
+map_out:
+ set_buffer_mapped(bh_result);
+out1:
+ if (allocated > max_blocks)
+ allocated = max_blocks;
+ ext4_ext_show_leaf(inode, path);
+ bh_result->b_bdev = inode->i_sb->s_bdev;
+ bh_result->b_blocknr = newblock;
+out2:
+ if (path) {
+ ext4_ext_drop_refs(path);
+ kfree(path);
+ }
+ return err ? err : allocated;
+}
+/*
* Block allocation/map/preallocation routine for extents based files
*
*
@@ -2859,33 +3155,10 @@ int ext4_ext_get_blocks(handle_t *handle
EXT4_EXT_CACHE_EXTENT);
goto out;
}
- if (flags & EXT4_GET_BLOCKS_UNINIT_EXT)
- goto out;
- if ((flags & EXT4_GET_BLOCKS_CREATE) == 0) {
- if (allocated > max_blocks)
- allocated = max_blocks;
- /*
- * We have blocks reserved already. We
- * return allocated blocks so that delalloc
- * won't do block reservation for us. But
- * the buffer head will be unmapped so that
- * a read from the block returns 0s.
- */
- set_buffer_unwritten(bh_result);
- bh_result->b_bdev = inode->i_sb->s_bdev;
- bh_result->b_blocknr = newblock;
- goto out2;
- }
-
- ret = ext4_ext_convert_to_initialized(handle, inode,
- path, iblock,
- max_blocks);
- if (ret <= 0) {
- err = ret;
- goto out2;
- } else
- allocated = ret;
- goto outnew;
+ ret = ext4_ext_handle_uninitialized_extents(handle,
+ inode, iblock, max_blocks, path,
+ flags, allocated, bh_result, newblock);
+ return ret;
}
}
@@ -2972,7 +3245,6 @@ int ext4_ext_get_blocks(handle_t *handle
/* previous routine could use block we allocated */
newblock = ext_pblock(&newex);
allocated = ext4_ext_get_actual_len(&newex);
-outnew:
set_buffer_new(bh_result);
/* Cache only when it is _not_ an uninitialized extent */
@@ -3171,6 +3443,77 @@ retry:
}
/*
+ * This function convert a range of blocks to written extents
+ * The caller of this function will pass the start offset and the size.
+ * all unwritten extents within this range will be converted to
+ * written extents.
+ *
+ * This function is called from the direct IO end io call back
+ * function, to convert the fallocated extents after IO is completed.
+ */
+int ext4_convert_unwritten_extents(struct inode *inode, loff_t offset,
+ loff_t len)
+{
+ handle_t *handle;
+ ext4_lblk_t block;
+ loff_t new_size;
+ unsigned int max_blocks;
+ int ret = 0;
+ int ret2 = 0;
+ struct buffer_head map_bh;
+ unsigned int credits, blkbits = inode->i_blkbits;
+
+ block = offset >> blkbits;
+ /*
+ * We can't just convert len to max_blocks because
+ * If blocksize = 4096 offset = 3072 and len = 2048
+ */
+ max_blocks = (EXT4_BLOCK_ALIGN(len + offset, blkbits) >> blkbits)
+ - block;
+ /*
+ * credits to insert 1 extent into extent tree
+ */
+ credits = ext4_chunk_trans_blocks(inode, max_blocks);
+ while (ret >= 0 && ret < max_blocks) {
+ block = block + ret;
+ max_blocks = max_blocks - ret;
+ handle = ext4_journal_start(inode, credits);
+ if (IS_ERR(handle)) {
+ ret = PTR_ERR(handle);
+ break;
+ }
+ map_bh.b_state = 0;
+ ret = ext4_get_blocks(handle, inode, block,
+ max_blocks, &map_bh,
+ EXT4_GET_BLOCKS_DIO_CONVERT_EXT);
+ if (ret <= 0) {
+ WARN_ON(ret <= 0);
+ printk(KERN_ERR "%s: ext4_ext_get_blocks "
+ "returned error inode#%lu, block=%u, "
+ "max_blocks=%u", __func__,
+ inode->i_ino, block, max_blocks);
+ ext4_mark_inode_dirty(handle, inode);
+ ret2 = ext4_journal_stop(handle);
+ break;
+ }
+
+ if ((block + ret) >= (EXT4_BLOCK_ALIGN(offset + len,
+ blkbits) >> blkbits))
+ new_size = offset + len;
+ else
+ new_size = (block + ret) << blkbits;
+
+ if (new_size > EXT4_I(inode)->i_disksize)
+ ext4_update_i_disksize(inode, new_size);
+
+ ext4_mark_inode_dirty(handle, inode);
+ ret2 = ext4_journal_stop(handle);
+ if (ret2)
+ break;
+ }
+ return ret > 0 ? ret2 : ret;
+}
+/*
* Callback function called for each extent to gather FIEMAP information.
*/
static int ext4_ext_fiemap_cb(struct inode *inode, struct ext4_ext_path *path,
--
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