On Oct 2, 2014, at 9:28 AM, Eric Sandeen <sandeen@xxxxxxxxxx> wrote:
> Delalloc write journal reservations only reserve 1 credit,
> to update the inode if necessary. However, it may happen
> once in a filesystem's lifetime that a file will cross
> the 2G threshold, and require the LARGE_FILE feature to
> be set in the superblock as well, if it was not set already.
>
> This overruns the transaction reservation, and can be
> demonstrated simply on any ext4 filesystem without the LARGE_FILE
> feature already set:
>
> dd if=/dev/zero of=testfile bs=1 seek=2147483646 count=1 \
> conv=notrunc of=testfile
> sync
> dd if=/dev/zero of=testfile bs=1 seek=2147483647 count=1 \
> conv=notrunc of=testfile
>
> leads to:
>
> EXT4-fs: ext4_do_update_inode:4296: aborting transaction: error 28 in __ext4_handle_dirty_super
> EXT4-fs error (device loop0) in ext4_do_update_inode:4301: error 28
> EXT4-fs error (device loop0) in ext4_reserve_inode_write:4757: Readonly filesystem
> EXT4-fs error (device loop0) in ext4_dirty_inode:4876: error 28
> EXT4-fs error (device loop0) in ext4_da_write_end:2685: error 28
>
> Adjust the number of credits based on whether the flag is
> already set, and whether the current write may extend past the
> LARGE_FILE limit.
>
> Signed-off-by: Eric Sandeen <sandeen@xxxxxxxxxx>
Reviewed-by: Andreas Dilger <adilger@xxxxxxxxx>
> ---
>
> Ok, how's this ... I do like this a lot better than the set-flag-on-
> mount-or-remount, which started to get a bit icky.
>
>
> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index 3aa26e9..8d362c2 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -2515,6 +2515,20 @@ static int ext4_nonda_switch(struct super_block *sb)
> return 0;
> }
>
> +/* We always reserve for an inode update; the superblock could be there too */
> +static int ext4_da_write_credits(struct inode *inode, loff_t pos, unsigned len)
> +{
> + if (EXT4_HAS_RO_COMPAT_FEATURE(inode->i_sb,
This could be marked "likely()" I suspect, but not critical.
> + EXT4_FEATURE_RO_COMPAT_LARGE_FILE))
> + return 1;
> +
> + if (pos + len <= 0x7fffffffULL)
> + return 1;
> +
> + /* We might need to update the superblock to set LARGE_FILE */
> + return 2;
> +}
> +
> static int ext4_da_write_begin(struct file *file, struct address_space *mapping,
> loff_t pos, unsigned len, unsigned flags,
> struct page **pagep, void **fsdata)
> @@ -2565,7 +2579,8 @@ retry_grab:
> * of file which has an already mapped buffer.
> */
> retry_journal:
> - handle = ext4_journal_start(inode, EXT4_HT_WRITE_PAGE, 1);
> + handle = ext4_journal_start(inode, EXT4_HT_WRITE_PAGE,
> + ext4_da_write_credits(inode, pos, len));
> if (IS_ERR(handle)) {
> page_cache_release(page);
> return PTR_ERR(handle);
>
> --
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Cheers, Andreas
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