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Use fallocate even if hole-punching unsupported (#5023)

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Summary:
The compiler flag `-DROCKSDB_FALLOCATE_PRESENT` was only set when
`fallocate`, `FALLOC_FL_KEEP_SIZE`, and `FALLOC_FL_PUNCH_HOLE` were all
present. However, the last of the three is not really necessary for the
primary `fallocate` use case; furthermore, it was introduced only in later
Linux kernel versions (2.6.38+).

This PR changes the flag `-DROCKSDB_FALLOCATE_PRESENT` to only require
`fallocate` and `FALLOC_FL_KEEP_SIZE` to be present. There is a separate
check for `FALLOC_FL_PUNCH_HOLE` only in the place where it is used.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5023

Differential Revision: D14248487

Pulled By: siying

fbshipit-source-id: a10ed0b902fa755988e957bd2dcec9081ec0502e
This commit is contained in:
Andrew Kryczka 2019-03-04 15:40:26 -08:00 committed by Facebook Github Bot
parent a283800616
commit 186b3afaa8
3 changed files with 4 additions and 3 deletions
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2
CMakeLists.txt
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@ -416,7 +416,7 @@ if(WITH_FALLOCATE)
#include <linux/falloc.h>
int main() {
int fd = open(\"/dev/null\", 0);
fallocate(fd, FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE, 0, 1024);
fallocate(fd, FALLOC_FL_KEEP_SIZE, 0, 1024);
}
" HAVE_FALLOCATE)
if(HAVE_FALLOCATE)

2
build_tools/build_detect_platform
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@ -234,7 +234,7 @@ else
#include <linux/falloc.h>
int main() {
int fd = open("/dev/null", 0);
fallocate(fd, FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE, 0, 1024);
fallocate(fd, FALLOC_FL_KEEP_SIZE, 0, 1024);
}
EOF
if [ "$?" = 0 ]; then

3
env/io_posix.cc vendored
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@ -825,7 +825,8 @@ Status PosixWritableFile::Close() {
// but it will be nice to log these errors.
int dummy __attribute__((__unused__));
dummy = ftruncate(fd_, filesize_);
#if defined(ROCKSDB_FALLOCATE_PRESENT) && !defined(TRAVIS)
#if defined(ROCKSDB_FALLOCATE_PRESENT) && defined(FALLOC_FL_PUNCH_HOLE) && \
!defined(TRAVIS)
// in some file systems, ftruncate only trims trailing space if the
// new file size is smaller than the current size. Calling fallocate
// with FALLOC_FL_PUNCH_HOLE flag to explicitly release these unused