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Message-Id: <1216401767.6869.19.camel@mingming-laptop>
Date: Fri, 18 Jul 2008 10:22:47 -0700
From: Mingming Cao <cmm@...ibm.com>
To: "Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
Cc: tytso@....edu, sandeen@...hat.com, linux-ext4@...r.kernel.org,
Shehjar Tikoo <shehjart@....unsw.edu.au>
Subject: Re: [PATCH] ext4: Fix data corruption when writing to prealloc area
在 2008-07-18五的 10:02 -0700，Mingming Cao写道：
> I tried this patch, with nodelalloc, the kernel did not crash! Previous
> it crashes in a few minutes.
>
> but the test did not stop after fill the file by specified 2G size
>
>
> I noticed the write() to write to the last fallocate extent(up to 2G)
> returns junk value.
>
>
> The testcase I got from Shehjart (who originally reported the problem)
> is
>
> http://www.gelato.unsw.edu.au/~shehjart/writefallocate.c
>
I forget to mention that I modify the test slight to call fallocate()
with default mode (expnd size) instead of keep size.
> command I use to reproduce the problem is
>
> ./writefallocate --filesize 2147483648 --wrblksize 65536 --fallocate
> 1048576 --filename /mnt/ext4/a --nounlink
>
> .............
> offset: 2147024896, written: 65536^M
> offset: 2147090432, written: 65536^M
> offset: 2147155968, written: 65536^M
> offset: 2147221504, written: 65536^M
> offset: 2147287040, written: 65536^M
> offset: 2147352576, written: 65536^M
> offset: 2147418112, written: 65535^M
> offset: 2147483647, written: 18446744073709551615^M
> fallocate offset: 2147483647^M
> offset: 2147483646, written: 18446744073709551615^M
> offset: 2147483645, written: 18446744073709551615^M
> offset: 2147483644, written: 18446744073709551615^M
> offset: 2147483643, written: 18446744073709551615^M
> offset: 2147483642, written: 18446744073709551615^M
> offset: 2147483641, written: 18446744073709551615^M
> offset: 2147483640, written: 18446744073709551615^M
>
>
> Appearently the test has fallocate/fill the 2G file, but since the last
> write() returns 18446744073709551615, the offset is decreased, cause the
> test continue with a break, and writes to wrong offset
>
>
>
>
> 在 2008-07-18五的 18:47 +0530，Aneesh Kumar K.V写道：
> > We need to recalucate the path information on extent insert
> > even if depth doesn't change.
> >
> > Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@...ux.vnet.ibm.com>
> > ---
> > fs/ext4/extents.c | 41 +++++++++++++++++++++++------------------
> > 1 files changed, 23 insertions(+), 18 deletions(-)
> >
> > diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
> > index 7bdaeec..9c8541e 100644
> > --- a/fs/ext4/extents.c
> > +++ b/fs/ext4/extents.c
> > @@ -2462,7 +2462,10 @@ static int ext4_ext_convert_to_initialized(handle_t *handle,
> > unsigned int newdepth;
> > /* If extent has less than EXT4_EXT_ZERO_LEN zerout directly */
> > if (allocated <= EXT4_EXT_ZERO_LEN) {
> > - /* Mark first half uninitialized.
> > + /*
> > + * iblock == ee_block is handled by the zerouout
> > + * at the beginning.
> > + * Mark first half uninitialized.
> > * Mark second half initialized and zero out the
> > * initialized extent
> > */
> > @@ -2485,7 +2488,7 @@ static int ext4_ext_convert_to_initialized(handle_t *handle,
> > 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)
> > @@ -2513,6 +2516,7 @@ static int ext4_ext_convert_to_initialized(handle_t *handle,
> > err = PTR_ERR(path);
> > return err;
> > }
> > + /* get the second half extent details */
> > ex = path[depth].p_ext;
> > err = ext4_ext_get_access(handle, inode,
> > path + depth);
> > @@ -2542,6 +2546,7 @@ static int ext4_ext_convert_to_initialized(handle_t *handle,
> > 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)
> > @@ -2557,23 +2562,22 @@ static int ext4_ext_convert_to_initialized(handle_t *handle,
> > */
> > orig_ex.ee_len = cpu_to_le16(ee_len -
> > ext4_ext_get_actual_len(ex3));
> > - if (newdepth != depth) {
> > - 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;
> > + 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 extent has less than EXT4_EXT_ZERO_LEN and we are trying
> > @@ -2591,6 +2595,7 @@ static int ext4_ext_convert_to_initialized(handle_t *handle,
> > ext4_ext_store_pblock(ex, ext_pblock(&orig_ex));
> > ext4_ext_dirty(handle, inode, path + depth);
> > /* zero out the first half */
> > + /* blocks available from iblock */
> > return allocated;
> > }
> > }
>
> --
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