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authorShehjar Tikoo <shehjart@gluster.com>2010-05-05 00:27:45 +0000
committerAnand V. Avati <avati@dev.gluster.com>2010-05-05 04:36:05 -0700
commitb0ed997cda2195e9178cbaa96d26976aa6dd2acf (patch)
tree49df25d9ef9af923cb1ef18d62bf3bf7dccc3002 /xlators/cluster/dht/src/dht-rename.c
parent716f4dc26097811161cbd59c919df11593cb46af (diff)
posix: Support thread-safe vectored writes/reads
..by maintaining internal offsets and using pwrite/pread instead of writev/read. The recent io-threads change is causing concurrent writes to a file from different io-threads. This results in a race between two threads both of which are trying to call lseek-writev. The lseek-writev sequence should be a critical section. This is where pwrite syscall helps. pwrite also requires an offset to be given so for supporting pwrites for multiple iovecs we maintain an offset within posix for the duration of the write fop and pass this internal offset to pwrite. The same logic also applies to read, only difference is that we do not need to read multiple iovecs but only provide an atomic lseek-read sequence. Signed-off-by: Shehjar Tikoo <shehjart@gluster.com> Signed-off-by: Anand V. Avati <avati@dev.gluster.com> BUG: 883 (Data corruption due to thread unsafe reads and writes) URL: http://bugs.gluster.com/cgi-bin/bugzilla3/show_bug.cgi?id=883
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