bug in block cache open call #1580
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…cate the file to zero. This is incorrect behaviour. We don't see it in the normal scenario as write-back cache is on by default. Hence all the open calls with O_WRONLY will be redirected O_RDWR. To simulate this turn of the write-back cache and then open file in O_WRONLY.
syeleti-msft
requested review from
vibhansa-msft,
souravgupta-msft,
ashruti-msft and
jainakanksha-msft
as code owners
| @@ -397,7 +397,7 @@ func (bc *BlockCache) OpenFile(options internal.OpenFileOptions) (*handlemap.Han | |||
| log.Debug("BlockCache::OpenFile : Size of file handle.Size %v", handle.Size) | |||
| bc.prepareHandleForBlockCache(handle) | |||
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| if options.Flags&os.O_TRUNC != 0 || (options.Flags&os.O_WRONLY != 0 && options.Flags&os.O_APPEND == 0) { | |||
| if options.Flags&os.O_TRUNC != 0 { | |||
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Earlier we were not changing the open flags in libfuse later due to some other issues we encountered we started doing that (opening all files in RDWR mode). Hence this check is independent and not relying on what libfuse does. Tomorow if we change that logic we need to remember to correct this flag here. Also, this is just in open and one time call, so it does not have any impact on the system. I suggest we leave this here as is as some day we might correct the libfuse behavior of overriding the flags.
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✅ What
current implementation of open file when opened in O_WRONLY will truncate the file to zero. This is incorrect behaviour.
👩🔬 How to validate if applicable
We don't see it in the normal scenario as write-back cache is on by default. Hence all the open calls with O_WRONLY will be redirected O_RDWR. To simulate this turn of the write-back cache while mounting with --disable-writeback-cache=true and then open file in O_WRONLY.