Eric Ren
2016-Aug-30 07:38 UTC
[Ocfs2-devel] [PATCH v2] ocfs2: Fix start offset to ocfs2_zero_range_for_truncate()
Hi, I'm on 4.8.0-rc3 kernel. Hope someone else can double-confirm this;-) On 08/30/2016 12:11 PM, Ashish Samant wrote:> Hmm, thats weird. I see this on 4.7 kernel without the patch: > > # xfs_io -c 'pwrite -b 4k 0 10M' -f 10MBfile > wrote 10485760/10485760 bytes at offset 0 > 10 MiB, 2560 ops; 0.0000 sec (683.995 MiB/sec and 175102.5992 ops/sec) > # reflink -f 10MBfile reflnktest > # fallocate -p -o 0 -l 1048615 reflnktest > # dd if=10MBfile iflag=direct bs=1048576 count=1 | hexdump -C > 00000000 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................| > * > 1+0 records in > 1+0 records out > 1048576 bytes (1.0 MB) copied, 0.0321517 s, 32.6 MB/s > 00100000 > > and with patch > ---- > # dd if=10MBfile iflag=direct bs=1M count=1 | hexdump -C > 00000000 cd cd cd cd cd cd cd cd cd cd cd cd cd cd cd cd |................|I'm not familiar with this code. So why is the output "cd ..."? because we didn't write anything into "10MBfile". Is it a magic number when reading from a hole? Eric> * > 1+0 records in > 1+0 records out > 00100000> > Thanks, > Ashish > > > On 08/29/2016 08:33 PM, Eric Ren wrote: >> Hello, >> >> On 08/30/2016 03:23 AM, Ashish Samant wrote: >>> Hi Eric, >>> >>> The easiest way to reproduce this is : >>> >>> 1. Create a random file of say 10 MB >>> xfs_io -c 'pwrite -b 4k 0 10M' -f 10MBfile >>> 2. Reflink it >>> reflink -f 10MBfile reflnktest >>> 3. Punch a hole at starting at cluster boundary with range greater that 1MB. You can >>> also use a range that will put the end offset in another extent. >>> fallocate -p -o 0 -l 1048615 reflnktest >>> 4. sync >>> 5. Check the first cluster in the source file. (It will be zeroed out). >>> dd if=10MBfile iflag=direct bs=<cluster size> count=1 | hexdump -C >> >> Thanks! I have a try myself, but I'm not sure what is our expected output and if the test >> result meet >> it: >> >> 1. After applying this patch: >> ocfs2dev1:/mnt/ocfs2 # rm 10MBfile reflnktest >> ocfs2dev1:/mnt/ocfs2 # xfs_io -c 'pwrite -b 4k 0 10M' -f 10MBfile >> wrote 10485760/10485760 bytes at offset 0 >> 10 MiB, 2560 ops; 0.0000 sec (1.089 GiB/sec and 285427.5839 ops/sec) >> ocfs2dev1:/mnt/ocfs2 # reflink -f 10MBfile reflnktest >> ocfs2dev1:/mnt/ocfs2 # fallocate -p -o 0 -l 1048615 reflnktest >> ocfs2dev1:/mnt/ocfs2 # dd if=10MBfile iflag=direct bs=1048576 count=1 | hexdump -C >> 00000000 cd cd cd cd cd cd cd cd cd cd cd cd cd cd cd cd |................| >> * >> 1+0 records in >> 1+0 records out >> 1048576 bytes (1.0 MB, 1.0 MiB) copied, 0.0952464 s, 11.0 MB/s >> 00100000 >> >> 2. Before this patch: >> .... >> ocfs2dev1:/mnt/ocfs2 # dd if=10MBfile iflag=direct bs=1048576 count=1 | hexdump -C >> 00000000 cd cd cd cd cd cd cd cd cd cd cd cd cd cd cd cd |................| >> * >> 1+0 records in >> 1+0 records out >> 1048576 bytes (1.0 MB, 1.0 MiB) copied, 0.0954648 s, 11.0 MB/s >> 00100000 >> >> 3. debugfs.ocfs2 -R stats /dev/sdb >> ... >> Block Size Bits: 12 Cluster Size Bits: 20 >> ... >> >> Eric >>> >>> Thanks, >>> Ashish >>> >>> On 08/28/2016 10:39 PM, Eric Ren wrote: >>>> Hi, >>>> >>>> Thanks for this fix. I'd like to reproduce this issue locally and test this patch, >>>> could you elaborate the detailed steps of reproduction? >>>> >>>> Thanks, >>>> Eric >>>> >>>> On 08/27/2016 07:04 AM, Ashish Samant wrote: >>>>> If we punch a hole on a reflink such that following conditions are met: >>>>> >>>>> 1. start offset is on a cluster boundary >>>>> 2. end offset is not on a cluster boundary >>>>> 3. (end offset is somewhere in another extent) or >>>>> (hole range > MAX_CONTIG_BYTES(1MB)), >>>>> >>>>> we dont COW the first cluster starting at the start offset. But in this >>>>> case, we were wrongly passing this cluster to >>>>> ocfs2_zero_range_for_truncate() to zero out. This will modify the cluster >>>>> in place and zero it in the source too. >>>>> >>>>> Fix this by skipping this cluster in such a scenario. >>>>> >>>>> Reported-by: Saar Maoz <saar.maoz at oracle.com> >>>>> Signed-off-by: Ashish Samant <ashish.samant at oracle.com> >>>>> Reviewed-by: Srinivas Eeda <srinivas.eeda at oracle.com> >>>>> --- >>>>> v1->v2: >>>>> -Changed the commit msg to include a better and generic description of >>>>> the problem, for all cluster sizes. >>>>> -Added Reported-by and Reviewed-by tags. >>>>> fs/ocfs2/file.c | 34 ++++++++++++++++++++++++---------- >>>>> 1 file changed, 24 insertions(+), 10 deletions(-) >>>>> >>>>> diff --git a/fs/ocfs2/file.c b/fs/ocfs2/file.c >>>>> index 4e7b0dc..0b055bf 100644 >>>>> --- a/fs/ocfs2/file.c >>>>> +++ b/fs/ocfs2/file.c >>>>> @@ -1506,7 +1506,8 @@ static int ocfs2_zero_partial_clusters(struct inode *inode, >>>>> u64 start, u64 len) >>>>> { >>>>> int ret = 0; >>>>> - u64 tmpend, end = start + len; >>>>> + u64 tmpend = 0; >>>>> + u64 end = start + len; >>>>> struct ocfs2_super *osb = OCFS2_SB(inode->i_sb); >>>>> unsigned int csize = osb->s_clustersize; >>>>> handle_t *handle; >>>>> @@ -1538,18 +1539,31 @@ static int ocfs2_zero_partial_clusters(struct inode *inode, >>>>> } >>>>> /* >>>>> - * We want to get the byte offset of the end of the 1st cluster. >>>>> + * If start is on a cluster boundary and end is somewhere in another >>>>> + * cluster, we have not COWed the cluster starting at start, unless >>>>> + * end is also within the same cluster. So, in this case, we skip this >>>>> + * first call to ocfs2_zero_range_for_truncate() truncate and move on >>>>> + * to the next one. >>>>> */ >>>>> - tmpend = (u64)osb->s_clustersize + (start & ~(osb->s_clustersize - 1)); >>>>> - if (tmpend > end) >>>>> - tmpend = end; >>>>> + if ((start & (csize - 1)) != 0) { >>>>> + /* >>>>> + * We want to get the byte offset of the end of the 1st >>>>> + * cluster. >>>>> + */ >>>>> + tmpend = (u64)osb->s_clustersize + >>>>> + (start & ~(osb->s_clustersize - 1)); >>>>> + if (tmpend > end) >>>>> + tmpend = end; >>>>> - trace_ocfs2_zero_partial_clusters_range1((unsigned long long)start, >>>>> - (unsigned long long)tmpend); >>>>> + trace_ocfs2_zero_partial_clusters_range1( >>>>> + (unsigned long long)start, >>>>> + (unsigned long long)tmpend); >>>>> - ret = ocfs2_zero_range_for_truncate(inode, handle, start, tmpend); >>>>> - if (ret) >>>>> - mlog_errno(ret); >>>>> + ret = ocfs2_zero_range_for_truncate(inode, handle, start, >>>>> + tmpend); >>>>> + if (ret) >>>>> + mlog_errno(ret); >>>>> + } >>>>> if (tmpend < end) { >>>>> /* >>>> >>>> >>> >> > >
Ashish Samant
2016-Aug-30 23:17 UTC
[Ocfs2-devel] [PATCH v2] ocfs2: Fix start offset to ocfs2_zero_range_for_truncate()
Hi Eric, I am able to reproduce this on 4.8.0-rc3 as well. Can you try again and issue a sync between fallocate and dd? On 08/30/2016 12:38 AM, Eric Ren wrote:> Hi, > > I'm on 4.8.0-rc3 kernel. Hope someone else can double-confirm this;-) > > On 08/30/2016 12:11 PM, Ashish Samant wrote: >> Hmm, thats weird. I see this on 4.7 kernel without the patch: >> >> # xfs_io -c 'pwrite -b 4k 0 10M' -f 10MBfile >> wrote 10485760/10485760 bytes at offset 0 >> 10 MiB, 2560 ops; 0.0000 sec (683.995 MiB/sec and 175102.5992 ops/sec) >> # reflink -f 10MBfile reflnktest >> # fallocate -p -o 0 -l 1048615 reflnktest >> # dd if=10MBfile iflag=direct bs=1048576 count=1 | hexdump -C >> 00000000 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 >> |................| >> * >> 1+0 records in >> 1+0 records out >> 1048576 bytes (1.0 MB) copied, 0.0321517 s, 32.6 MB/s >> 00100000 >> >> and with patch >> ---- >> # dd if=10MBfile iflag=direct bs=1M count=1 | hexdump -C >> 00000000 cd cd cd cd cd cd cd cd cd cd cd cd cd cd cd cd >> |................| > > I'm not familiar with this code. So why is the output "cd ..."? > because we didn't write anything > into "10MBfile". Is it a magic number when reading from a hole?No, "cd" is what xfs_io wrote into the file. Those are the original contents of the file which are overwritten by 0 in the first cluster because of this bug. Thanks, Ashish> > Eric > >> * >> 1+0 records in >> 1+0 records out >> 00100000 > > > >> >> Thanks, >> Ashish >> >> >> On 08/29/2016 08:33 PM, Eric Ren wrote: >>> Hello, >>> >>> On 08/30/2016 03:23 AM, Ashish Samant wrote: >>>> Hi Eric, >>>> >>>> The easiest way to reproduce this is : >>>> >>>> 1. Create a random file of say 10 MB >>>> xfs_io -c 'pwrite -b 4k 0 10M' -f 10MBfile >>>> 2. Reflink it >>>> reflink -f 10MBfile reflnktest >>>> 3. Punch a hole at starting at cluster boundary with range greater >>>> that 1MB. You can also use a range that will put the end offset in >>>> another extent. >>>> fallocate -p -o 0 -l 1048615 reflnktest >>>> 4. sync >>>> 5. Check the first cluster in the source file. (It will be zeroed >>>> out). >>>> dd if=10MBfile iflag=direct bs=<cluster size> count=1 | hexdump -C >>> >>> Thanks! I have a try myself, but I'm not sure what is our expected >>> output and if the test result meet >>> it: >>> >>> 1. After applying this patch: >>> ocfs2dev1:/mnt/ocfs2 # rm 10MBfile reflnktest >>> ocfs2dev1:/mnt/ocfs2 # xfs_io -c 'pwrite -b 4k 0 10M' -f 10MBfile >>> wrote 10485760/10485760 bytes at offset 0 >>> 10 MiB, 2560 ops; 0.0000 sec (1.089 GiB/sec and 285427.5839 ops/sec) >>> ocfs2dev1:/mnt/ocfs2 # reflink -f 10MBfile reflnktest >>> ocfs2dev1:/mnt/ocfs2 # fallocate -p -o 0 -l 1048615 reflnktest >>> ocfs2dev1:/mnt/ocfs2 # dd if=10MBfile iflag=direct bs=1048576 >>> count=1 | hexdump -C >>> 00000000 cd cd cd cd cd cd cd cd cd cd cd cd cd cd cd cd >>> |................| >>> * >>> 1+0 records in >>> 1+0 records out >>> 1048576 bytes (1.0 MB, 1.0 MiB) copied, 0.0952464 s, 11.0 MB/s >>> 00100000 >>> >>> 2. Before this patch: >>> .... >>> ocfs2dev1:/mnt/ocfs2 # dd if=10MBfile iflag=direct bs=1048576 >>> count=1 | hexdump -C >>> 00000000 cd cd cd cd cd cd cd cd cd cd cd cd cd cd cd cd >>> |................| >>> * >>> 1+0 records in >>> 1+0 records out >>> 1048576 bytes (1.0 MB, 1.0 MiB) copied, 0.0954648 s, 11.0 MB/s >>> 00100000 >>> >>> 3. debugfs.ocfs2 -R stats /dev/sdb >>> ... >>> Block Size Bits: 12 Cluster Size Bits: 20 >>> ... >>> >>> Eric >>>> >>>> Thanks, >>>> Ashish >>>> >>>> On 08/28/2016 10:39 PM, Eric Ren wrote: >>>>> Hi, >>>>> >>>>> Thanks for this fix. I'd like to reproduce this issue locally and >>>>> test this patch, >>>>> could you elaborate the detailed steps of reproduction? >>>>> >>>>> Thanks, >>>>> Eric >>>>> >>>>> On 08/27/2016 07:04 AM, Ashish Samant wrote: >>>>>> If we punch a hole on a reflink such that following conditions >>>>>> are met: >>>>>> >>>>>> 1. start offset is on a cluster boundary >>>>>> 2. end offset is not on a cluster boundary >>>>>> 3. (end offset is somewhere in another extent) or >>>>>> (hole range > MAX_CONTIG_BYTES(1MB)), >>>>>> >>>>>> we dont COW the first cluster starting at the start offset. But >>>>>> in this >>>>>> case, we were wrongly passing this cluster to >>>>>> ocfs2_zero_range_for_truncate() to zero out. This will modify the >>>>>> cluster >>>>>> in place and zero it in the source too. >>>>>> >>>>>> Fix this by skipping this cluster in such a scenario. >>>>>> >>>>>> Reported-by: Saar Maoz <saar.maoz at oracle.com> >>>>>> Signed-off-by: Ashish Samant <ashish.samant at oracle.com> >>>>>> Reviewed-by: Srinivas Eeda <srinivas.eeda at oracle.com> >>>>>> --- >>>>>> v1->v2: >>>>>> -Changed the commit msg to include a better and generic >>>>>> description of >>>>>> the problem, for all cluster sizes. >>>>>> -Added Reported-by and Reviewed-by tags. >>>>>> fs/ocfs2/file.c | 34 ++++++++++++++++++++++++---------- >>>>>> 1 file changed, 24 insertions(+), 10 deletions(-) >>>>>> >>>>>> diff --git a/fs/ocfs2/file.c b/fs/ocfs2/file.c >>>>>> index 4e7b0dc..0b055bf 100644 >>>>>> --- a/fs/ocfs2/file.c >>>>>> +++ b/fs/ocfs2/file.c >>>>>> @@ -1506,7 +1506,8 @@ static int >>>>>> ocfs2_zero_partial_clusters(struct inode *inode, >>>>>> u64 start, u64 len) >>>>>> { >>>>>> int ret = 0; >>>>>> - u64 tmpend, end = start + len; >>>>>> + u64 tmpend = 0; >>>>>> + u64 end = start + len; >>>>>> struct ocfs2_super *osb = OCFS2_SB(inode->i_sb); >>>>>> unsigned int csize = osb->s_clustersize; >>>>>> handle_t *handle; >>>>>> @@ -1538,18 +1539,31 @@ static int >>>>>> ocfs2_zero_partial_clusters(struct inode *inode, >>>>>> } >>>>>> /* >>>>>> - * We want to get the byte offset of the end of the 1st >>>>>> cluster. >>>>>> + * If start is on a cluster boundary and end is somewhere in >>>>>> another >>>>>> + * cluster, we have not COWed the cluster starting at start, >>>>>> unless >>>>>> + * end is also within the same cluster. So, in this case, we >>>>>> skip this >>>>>> + * first call to ocfs2_zero_range_for_truncate() truncate >>>>>> and move on >>>>>> + * to the next one. >>>>>> */ >>>>>> - tmpend = (u64)osb->s_clustersize + (start & >>>>>> ~(osb->s_clustersize - 1)); >>>>>> - if (tmpend > end) >>>>>> - tmpend = end; >>>>>> + if ((start & (csize - 1)) != 0) { >>>>>> + /* >>>>>> + * We want to get the byte offset of the end of the 1st >>>>>> + * cluster. >>>>>> + */ >>>>>> + tmpend = (u64)osb->s_clustersize + >>>>>> + (start & ~(osb->s_clustersize - 1)); >>>>>> + if (tmpend > end) >>>>>> + tmpend = end; >>>>>> - trace_ocfs2_zero_partial_clusters_range1((unsigned long >>>>>> long)start, >>>>>> - (unsigned long long)tmpend); >>>>>> + trace_ocfs2_zero_partial_clusters_range1( >>>>>> + (unsigned long long)start, >>>>>> + (unsigned long long)tmpend); >>>>>> - ret = ocfs2_zero_range_for_truncate(inode, handle, start, >>>>>> tmpend); >>>>>> - if (ret) >>>>>> - mlog_errno(ret); >>>>>> + ret = ocfs2_zero_range_for_truncate(inode, handle, start, >>>>>> + tmpend); >>>>>> + if (ret) >>>>>> + mlog_errno(ret); >>>>>> + } >>>>>> if (tmpend < end) { >>>>>> /* >>>>> >>>>> >>>> >>> >> >> >