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Date: Fri, 07 Mar 2008 09:57:47 -0600
From: Eric Sandeen <sandeen@...hat.com>
To: "Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
CC: cmm@...ibm.com, tytso@....edu, linux-ext4@...r.kernel.org
Subject: Re: [RFC PATCH] ext4: Fix fallocate to update the file size in each
transaction.
Eric Sandeen wrote:
> Aneesh Kumar K.V wrote:
>> ext4_fallocate need to update file size in each transaction. Otherwise
>> ife we crash the file size won't be updated. We were also not marking
>> the inode dirty after updating file size before.
>
> This led to losing the size update when unmounted...
>
>> Also when we try to
>> retry allocation due to ENOSPC make sure we reset the variable ret so
>> that we actually do a retry.
>
> That's a few alsos. Should this be more than one patch when committed?
>
> -Eric
Oops that "-Eric" was too soon, there are more comments below ;)
>> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@...ux.vnet.ibm.com>
>> ---
>> fs/ext4/extents.c | 78 +++++++++++++++++++++--------------------------------
>> 1 files changed, 31 insertions(+), 47 deletions(-)
>>
>> diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
>> index dcdf92a..09dd3c5 100644
>> --- a/fs/ext4/extents.c
>> +++ b/fs/ext4/extents.c
>> @@ -2783,6 +2783,26 @@ int ext4_ext_writepage_trans_blocks(struct inode *inode, int num)
>> return needed;
>> }
>>
>> +static void ext4_falloc_update_inode(struct inode *inode,
>> + int mode, loff_t new_size)
>> +{
>> + struct timespec now;
>> +
>> + now = current_fs_time(inode->i_sb);
>> + if (!timespec_equal(&inode->i_ctime, &now))
>> + inode->i_ctime = now;
>
> This used to depend on blocks actually being allocated; it looks like it
> doesn't anymore?
>
>> + /*
>> + * Update only when preallocation was requested beyond
>> + * the file size.
>> + */
>> + if (!(mode & FALLOC_FL_KEEP_SIZE) &&
>> + new_size > i_size_read(inode)) {
>> + i_size_write(inode, new_size);
>> + EXT4_I(inode)->i_disksize = i_size_read(inode);
>> + }
>> +
>> +}
>
> Ok, I think this is all cleaner...
>
>> /*
>> * preallocate space for a file. This implements ext4's fallocate inode
>> * operation, which gets called from sys_fallocate system call.
>> @@ -2794,8 +2814,8 @@ long ext4_fallocate(struct inode *inode, int mode, loff_t offset, loff_t len)
>> {
>> handle_t *handle;
>> ext4_lblk_t block;
>> + loff_t new_size;
>> unsigned long max_blocks;
>> - ext4_fsblk_t nblocks = 0;
>> int ret = 0;
>> int ret2 = 0;
>> int retries = 0;
>> @@ -2814,8 +2834,7 @@ long ext4_fallocate(struct inode *inode, int mode, loff_t offset, loff_t len)
>> return -ENODEV;
>>
>> block = offset >> blkbits;
>> - max_blocks = (EXT4_BLOCK_ALIGN(len + offset, blkbits) >> blkbits)
>> - - block;
>> + max_blocks = EXT4_BLOCK_ALIGN(len, blkbits) >> blkbits;
>
> Ok, this makes much more sense IMHO.
>
>>
>> /*
>> * credits to insert 1 extent into extent tree + buffers to be able to
>> @@ -2848,28 +2867,13 @@ retry:
>> ret2 = ext4_journal_stop(handle);
>> break;
>> }
>> - if (ret > 0) {
>> - /* check wrap through sign-bit/zero here */
>> - if ((block + ret) < 0 || (block + ret) < block) {
>> - ret = -EIO;
>> - ext4_mark_inode_dirty(handle, inode);
>> - ret2 = ext4_journal_stop(handle);
>> - break;
>> - }
>> - if (buffer_new(&map_bh) && ((block + ret) >
>> - (EXT4_BLOCK_ALIGN(i_size_read(inode), blkbits)
>> - >> blkbits)))
>> - nblocks = nblocks + ret;
>> - }
>> + if ((block + ret) >= (EXT4_BLOCK_ALIGN(offset + len,
>> + blkbits) >> blkbits))
>> + new_size = offset + len;
>> + else
>> + new_size = (block + ret) << blkbits;
>
> Since we called ext4_get_blocks_wrap with max_blocks, will we really end
> up with more blocks allocated than we asked for? And do we no longer
> need the wrap checks? (I'd expect that to be tested higher up with the
> original offset+len requested, no?)
>
>> - /* Update ctime if new blocks get allocated */
>> - if (nblocks) {
>> - struct timespec now;
>> -
>> - now = current_fs_time(inode->i_sb);
>> - if (!timespec_equal(&inode->i_ctime, &now))
>> - inode->i_ctime = now;
>> - }
>> + ext4_falloc_update_inode(inode, mode, new_size);
>>
>> ext4_mark_inode_dirty(handle, inode);
>> ret2 = ext4_journal_stop(handle);
>> @@ -2877,30 +2881,10 @@ retry:
>> break;
>> }
>>
>> - if (ret == -ENOSPC && ext4_should_retry_alloc(inode->i_sb, &retries))
>> + if (ret == -ENOSPC &&
>> + ext4_should_retry_alloc(inode->i_sb, &retries)) {
>> + ret = 0;
>> goto retry;
>> -
>> - /*
>> - * Time to update the file size.
>> - * Update only when preallocation was requested beyond the file size.
>> - */
>> - if (!(mode & FALLOC_FL_KEEP_SIZE) &&
>> - (offset + len) > i_size_read(inode)) {
>> - if (ret > 0) {
>> - /*
>> - * if no error, we assume preallocation succeeded
>> - * completely
>> - */
>> - i_size_write(inode, offset + len);
>> - EXT4_I(inode)->i_disksize = i_size_read(inode);
>> - } else if (ret < 0 && nblocks) {
>> - /* Handle partial allocation scenario */
>> - loff_t newsize;
>> -
>> - newsize = (nblocks << blkbits) + i_size_read(inode);
>> - i_size_write(inode, EXT4_BLOCK_ALIGN(newsize, blkbits));
>> - EXT4_I(inode)->i_disksize = i_size_read(inode);
>> - }
>> }
>>
>> mutex_unlock(&inode->i_mutex);
>
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