Ashish Samant
2016-Aug-30 04:11 UTC
[Ocfs2-devel] [PATCH v2] ocfs2: Fix start offset to ocfs2_zero_range_for_truncate()
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 |................| * 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) { >>>> /* >>> >>> >> >
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) { >>>>> /* >>>> >>>> >>> >> > >