On 2011-05-13, at 12:34 AM, Lukas Czerner wrote: > On Wed, 11 May 2011, Kazuya Mio wrote: >> We hit BUG_ON in ext4_ext_put_gap_in_cache() while creating a file >> whose size is the max file size of extent format. Because the extent cache >> length is 0 when we allocate two blocks to the file offset 2^32-2, and then >> the offset 2^32-1. To fix it, we decrease the max file size to >> (2^32-2)*blocksize. In this way, we would be able to allocate a block up to >> the offset 2^32-2. I think there is no data loss because we can read all files >> created before applying this patch. >> >> How to reproduce: >> I'm running 2.6.39-rc6. Note that i386 architecture and 4KB blocksize cannot >> reproduce this problem. >> >> # dd if=/dev/zero of=/mnt/mp1/file bs=<blocksize> count=1 seek=$((2**32-2)) >> # sync >> # dd if=/dev/zero of=/mnt/mp1/file bs=<blocksize> count=1 seek=$((2**32-1)) > > Hi Kazuya, > > Thanks for the patch, however I think that there is a better solution > than lowering the max file size, which is not necessary. I would rather > fix ext4_ext_put_gap_in_cache() and allow to invalidate the cache by > setting the length to zero. > > Please see the following patch, if it works for you. This thread has stalled. Until we can come up with a better fix, I think we should land Kazuya's patch for the current merge window and then worry about allocating that last 4kB at the end of the 16TB file later (2.3e-6% of the file :-). >> Signed-off-by: Kazuya Mio <k-mio@xxxxxxxxxxxxx> >> --- >> fs/ext4/super.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> diff --git a/fs/ext4/super.c b/fs/ext4/super.c >> index 8553dfb..fce0249 100644 >> --- a/fs/ext4/super.c >> +++ b/fs/ext4/super.c >> @@ -2248,8 +2248,8 @@ static loff_t ext4_max_size(int blkbits, int has_huge_files) >> >> /* 32-bit extent-start container, ee_block */ >> res = 1LL << 32; >> - res <<= blkbits; >> res -= 1; >> + res <<= blkbits; >> >> /* Sanity check against vm- & vfs- imposed limits */ >> if (res > upper_limit) >> >> -- >> To unsubscribe from this list: send the line "unsubscribe linux-ext4" in >> the body of a message to majordomo@xxxxxxxxxxxxxxx >> More majordomo info at http://vger.kernel.org/majordomo-info.html >> > -- > To unsubscribe from this list: send the line "unsubscribe linux-ext4" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html Cheers, Andreas -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
