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Date: Fri, 09 Apr 2010 21:18:18 +0400
From: Dmitry Monakhov <dmonakhov@...nvz.org>
To: linux-ext4@...r.kernel.org
Cc: aneesh.kumar@...ux.vnet.ibm.com, tytso@....edu
Subject: Re: [PATCH] ext4: Do not zeroout uninitialized extents beyond i_size
Dmitry Monakhov <dmonakhov@...nvz.org> writes:
> diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
> index 8bdee27..54a9b80 100644
> --- a/fs/ext4/extents.c
> +++ b/fs/ext4/extents.c
> @@ -1,3 +1,4 @@
> +
> /*
> * Copyright (c) 2003-2006, Cluster File Systems, Inc, info@...sterfs.com
> * Written by Alex Tomas <alex@...sterfs.com>
> @@ -2540,9 +2541,11 @@ static void bi_complete(struct bio *bio, int error)
> {
> complete((struct completion *)bio->bi_private);
> }
> -
> +#define ext4_ext_zeroout(inode,ext_nn) \
> + __ext4_ext_zeroout(inode, ext_nn, iblock, max_blocks)
> /* FIXME!! we need to try to merge to left or right after zero-out */
> -static int ext4_ext_zeroout(struct inode *inode, struct ext4_extent *ex)
> +static int __ext4_ext_zeroout(struct inode *inode, struct ext4_extent *ex,
> + ext4_lblk_t iblock, unsigned int max_blocks)
Oops, sorry, wrong patch attached :).
> {
> int ret;
> struct bio *bio;
> @@ -2560,6 +2563,12 @@ static int ext4_ext_zeroout(struct inode *inode, struct ext4_extent *ex)
> /* convert ee_pblock to 512 byte sectors */
> ee_pblock = ee_pblock << (blkbits - 9);
>
> + printk("%s inode:%lu ext:[%d:%d] iblock:%d max:%d i_sz:%lld expand:%d\n",
> + __FUNCTION__, inode->i_ino,
> + le32_to_cpu(ex->ee_block), ee_len,
> + iblock, max_blocks, inode->i_size,
> + ((inode->i_size +blocksize -1) >> blkbits) < iblock + max_blocks);
> +
> while (ee_len > 0) {
>
> if (ee_len > BIO_MAX_PAGES)
> @@ -2631,11 +2640,15 @@ static int ext4_ext_convert_to_initialized(handle_t *handle,
> struct ext4_extent *ex2 = NULL;
> struct ext4_extent *ex3 = NULL;
> struct ext4_extent_header *eh;
> - ext4_lblk_t ee_block;
> + ext4_lblk_t ee_block, eof_block;
> unsigned int allocated, ee_len, depth;
> ext4_fsblk_t newblock;
> int err = 0;
> int ret = 0;
> + int may_zeroout;
> + ext_debug("ext4_ext_convert_to_initialized: inode %lu, logical"
> + "block %llu, max_blocks %u ",
> + inode->i_ino, (unsigned long long)iblock, max_blocks);
>
> depth = ext_depth(inode);
> eh = path[depth].p_hdr;
> @@ -2644,16 +2657,25 @@ static int ext4_ext_convert_to_initialized(handle_t *handle,
> ee_len = ext4_ext_get_actual_len(ex);
> allocated = ee_len - (iblock - ee_block);
> newblock = iblock - ee_block + ext_pblock(ex);
> + eof_block = (inode->i_size + inode->i_sb->s_blocksize - 1) >>
> + inode->i_sb->s_blocksize_bits;
> 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));
>
> + /*
> + * It is safe to convert extent to initialized via explicit
> + * zeroout only if extent is fully insde i_size or new_size.
> + */
> + may_zeroout = ee_block + ee_len <= iblock + max_blocks ||
> + ee_block + ee_len <= eof_block;
> +
> err = ext4_ext_get_access(handle, inode, path + depth);
> if (err)
> goto out;
> /* If extent has less than 2*EXT4_EXT_ZERO_LEN zerout directly */
> - if (ee_len <= 2*EXT4_EXT_ZERO_LEN) {
> + if (ee_len <= 2*EXT4_EXT_ZERO_LEN && may_zeroout) {
> err = ext4_ext_zeroout(inode, &orig_ex);
> if (err)
> goto fix_extent_len;
> @@ -2684,7 +2706,7 @@ static int ext4_ext_convert_to_initialized(handle_t *handle,
> if (allocated > max_blocks) {
> unsigned int newdepth;
> /* If extent has less than EXT4_EXT_ZERO_LEN zerout directly */
> - if (allocated <= EXT4_EXT_ZERO_LEN) {
> + if (allocated <= EXT4_EXT_ZERO_LEN && may_zeroout) {
> /*
> * iblock == ee_block is handled by the zerouout
> * at the beginning.
> @@ -2760,7 +2782,7 @@ static int ext4_ext_convert_to_initialized(handle_t *handle,
> ex3->ee_len = cpu_to_le16(allocated - max_blocks);
> ext4_ext_mark_uninitialized(ex3);
> err = ext4_ext_insert_extent(handle, inode, path, ex3, 0);
> - if (err == -ENOSPC) {
> + if (err == -ENOSPC && may_zeroout) {
> err = ext4_ext_zeroout(inode, &orig_ex);
> if (err)
> goto fix_extent_len;
> @@ -2784,8 +2806,11 @@ static int ext4_ext_convert_to_initialized(handle_t *handle,
> * 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));
> + ee_len -= ext4_ext_get_actual_len(ex3);
> + orig_ex.ee_len = cpu_to_le16(ee_len);
> + may_zeroout = ee_block + ee_len <= iblock + max_blocks ||
> + ee_block + ee_len <= eof_block;
> +
> depth = newdepth;
> ext4_ext_drop_refs(path);
> path = ext4_ext_find_extent(inode, iblock, path);
> @@ -2809,7 +2834,7 @@ static int ext4_ext_convert_to_initialized(handle_t *handle,
> * otherwise give the extent a chance to merge to left
> */
> if (le16_to_cpu(orig_ex.ee_len) <= EXT4_EXT_ZERO_LEN &&
> - iblock != ee_block) {
> + iblock != ee_block && may_zeroout) {
> err = ext4_ext_zeroout(inode, &orig_ex);
> if (err)
> goto fix_extent_len;
> @@ -2878,7 +2903,7 @@ static int ext4_ext_convert_to_initialized(handle_t *handle,
> goto out;
> insert:
> err = ext4_ext_insert_extent(handle, inode, path, &newex, 0);
> - if (err == -ENOSPC) {
> + if (err == -ENOSPC && may_zeroout) {
> err = ext4_ext_zeroout(inode, &orig_ex);
> if (err)
> goto fix_extent_len;
> @@ -2938,14 +2963,16 @@ static int ext4_split_unwritten_extents(handle_t *handle,
> struct ext4_extent *ex2 = NULL;
> struct ext4_extent *ex3 = NULL;
> struct ext4_extent_header *eh;
> - ext4_lblk_t ee_block;
> + ext4_lblk_t ee_block, eof_block;
> unsigned int allocated, ee_len, depth;
> ext4_fsblk_t newblock;
> int err = 0;
> + int may_zeroout;
>
> ext_debug("ext4_split_unwritten_extents: inode %lu,"
> "iblock %llu, max_blocks %u\n", inode->i_ino,
> (unsigned long long)iblock, max_blocks);
> +
> depth = ext_depth(inode);
> eh = path[depth].p_hdr;
> ex = path[depth].p_ext;
> @@ -2953,10 +2980,19 @@ static int ext4_split_unwritten_extents(handle_t *handle,
> ee_len = ext4_ext_get_actual_len(ex);
> allocated = ee_len - (iblock - ee_block);
> newblock = iblock - ee_block + ext_pblock(ex);
> + eof_block = (inode->i_size + inode->i_sb->s_blocksize - 1) >>
> + inode->i_sb->s_blocksize_bits;
> +
> 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));
> + /*
> + * It is safe to convert extent to initialized via explicit
> + * zeroout only if extent is fully insde i_size or new_size.
> + */
> + may_zeroout = ee_block + ee_len <= iblock + max_blocks ||
> + ee_block + ee_len <= eof_block;
>
> /*
> * If the uninitialized extent begins at the same logical
> @@ -2992,7 +3028,7 @@ static int ext4_split_unwritten_extents(handle_t *handle,
> ex3->ee_len = cpu_to_le16(allocated - max_blocks);
> ext4_ext_mark_uninitialized(ex3);
> err = ext4_ext_insert_extent(handle, inode, path, ex3, flags);
> - if (err == -ENOSPC) {
> + if (err == -ENOSPC && may_zeroout) {
> err = ext4_ext_zeroout(inode, &orig_ex);
> if (err)
> goto fix_extent_len;
> @@ -3063,7 +3099,7 @@ static int ext4_split_unwritten_extents(handle_t *handle,
> goto out;
> insert:
> err = ext4_ext_insert_extent(handle, inode, path, &newex, flags);
> - if (err == -ENOSPC) {
> + if (err == -ENOSPC && may_zeroout) {
> err = ext4_ext_zeroout(inode, &orig_ex);
> if (err)
> goto fix_extent_len;
--
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