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Sat, 12 Oct 2024 07:18:42 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id a3dfD9IiCmcbIQAAD6G6ig (envelope-from ); Sat, 12 Oct 2024 07:18:42 +0000 From: Qu Wenruo To: linux-btrfs@vger.kernel.org, fstests@vger.kernel.org Subject: [PATCH] fstests: btrfs/002: fix the OOM caused by too large block size Date: Sat, 12 Oct 2024 17:48:24 +1030 Message-ID: <20241012071824.124468-1-wqu@suse.com> X-Mailer: git-send-email 2.47.0 Precedence: bulk X-Mailing-List: linux-btrfs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Rspamd-Queue-Id: 7A4FF1FF1E X-Spam-Score: -3.01 X-Rspamd-Action: no action X-Spamd-Result: default: False [-3.01 / 50.00]; BAYES_HAM(-3.00)[100.00%]; MID_CONTAINS_FROM(1.00)[]; NEURAL_HAM_LONG(-1.00)[-1.000]; R_MISSING_CHARSET(0.50)[]; R_DKIM_ALLOW(-0.20)[suse.com:s=susede1]; NEURAL_HAM_SHORT(-0.20)[-1.000]; MIME_GOOD(-0.10)[text/plain]; MX_GOOD(-0.01)[]; RECEIVED_SPAMHAUS_BLOCKED_OPENRESOLVER(0.00)[2a07:de40:b281:106:10:150:64:167:received]; ARC_NA(0.00)[]; RCVD_VIA_SMTP_AUTH(0.00)[]; FUZZY_BLOCKED(0.00)[rspamd.com]; MIME_TRACE(0.00)[0:+]; RBL_SPAMHAUS_BLOCKED_OPENRESOLVER(0.00)[2a07:de40:b281:104:10:150:64:97:from]; DBL_BLOCKED_OPENRESOLVER(0.00)[suse.com:dkim,suse.com:mid,suse.com:email,imap1.dmz-prg2.suse.org:rdns,imap1.dmz-prg2.suse.org:helo]; RCPT_COUNT_TWO(0.00)[2]; DKIM_SIGNED(0.00)[suse.com:s=susede1]; FROM_EQ_ENVFROM(0.00)[]; FROM_HAS_DN(0.00)[]; SPAMHAUS_XBL(0.00)[2a07:de40:b281:104:10:150:64:97:from]; RCVD_TLS_ALL(0.00)[]; TO_DN_NONE(0.00)[]; RCVD_COUNT_TWO(0.00)[2]; TO_MATCH_ENVRCPT_ALL(0.00)[]; DKIM_TRACE(0.00)[suse.com:+] X-Rspamd-Server: rspamd1.dmz-prg2.suse.org X-Spam-Flag: NO X-Spam-Level: [BUG] When running the test case btrfs/002, with 64K page size and 64K sector size, and the VM doesn't have much memory (in my case 4G Vram), the test case will trigger OOM and fail: btrfs/002 4s ... [failed, exit status 1]- output mismatch (see /home/adam/xfstests-dev/results//btrfs/002.out.bad) --- tests/btrfs/002.out 2024-04-25 18:13:45.035555469 +0930 +++ /home/adam/xfstests-dev/results//btrfs/002.out.bad 2024-10-12 17:19:48.785156223 +1030 @@ -1,2 +1 @@ QA output created by 002 -Silence is golden ... The OOM is triggered by the dd process, and a lot of dd processes are using too much memory: dd invoked oom-killer: gfp_mask=0x140dca(GFP_HIGHUSER_MOVABLE|__GFP_COMP|__GFP_ZERO), order=0, oom_score_adj=250 CPU: 0 UID: 0 PID: 185764 Comm: dd Not tainted 6.12.0-rc2-custom+ #76 Hardware name: QEMU KVM Virtual Machine, BIOS unknown 2/2/2022 Tasks state (memory values in pages): [ pid ] uid tgid total_vm rss rss_anon rss_file rss_shmem pgtables_bytes swapents oom_score_adj name [ 185665] 0 185665 8688 3840 3840 0 0 458752 4832 250 dd [ 185672] 0 185672 8688 2432 2432 0 0 393216 5312 250 dd [ 185680] 0 185680 8688 2016 2016 0 0 458752 4960 250 dd [ 185686] 0 185686 8688 2080 2080 0 0 458752 3584 250 dd [ 185693] 0 185693 8688 2144 2144 0 0 458752 4384 250 dd [ 185700] 0 185700 8688 2176 2176 0 0 458752 3584 250 dd [ 185707] 0 185707 8688 1792 1792 0 0 524288 3616 250 dd [ 185714] 0 185714 8688 2304 2304 0 0 458752 3488 250 dd [ 185721] 0 185721 8688 1920 1920 0 0 458752 2624 250 dd [ 185728] 0 185728 8688 2272 2272 0 0 393216 2528 250 dd [ 185735] 0 185735 8688 2048 2048 0 0 393216 3552 250 dd [ 185742] 0 185742 8688 1984 1984 0 0 458752 2816 250 dd [ 185751] 0 185751 8688 1600 1600 0 0 458752 2784 250 dd [ 185756] 0 185756 8688 1120 1120 0 0 458752 2400 250 dd [ 185764] 0 185764 8688 1504 1504 0 0 393216 2240 250 dd [ 185772] 0 185772 8688 1504 1504 0 0 458752 1984 250 dd [ 185777] 0 185777 8688 1280 1280 0 0 393216 2336 250 dd [ 185784] 0 185784 8688 2144 2144 0 0 393216 2272 250 dd [ 185791] 0 185791 8688 2176 2176 0 0 458752 576 250 dd [ 185798] 0 185798 8688 1696 1696 0 0 458752 1536 250 dd [ 185806] 0 185806 8688 1728 1728 0 0 393216 544 250 dd [ 185815] 0 185815 8688 2240 2240 0 0 458752 0 250 dd [ 185819] 0 185819 8688 1504 1504 0 0 458752 384 250 dd [ 185826] 0 185826 8688 1536 1536 0 0 458752 160 250 dd [ 185833] 0 185833 8688 2944 2944 0 0 458752 64 250 dd [ 185838] 0 185838 8688 2400 2400 0 0 458752 0 250 dd [ 185847] 0 185847 8688 864 864 0 0 458752 0 250 dd [ 185853] 0 185853 8688 1088 1088 0 0 393216 0 250 dd [ 185860] 0 185860 8688 416 416 0 0 393216 0 250 dd [ 185867] 0 185867 8688 352 352 0 0 458752 0 250 dd [CAUSE] The test case workload _fill_blk() is going to fill the file to its block boundary. But the implementation is not taking larger blocks into consideration. FSIZE=`stat -t $i | cut -d" " -f2` BLKS=`stat -c "%B" $i` NBLK=`stat -c "%b" $i` FALLOC=$(($BLKS * $NBLK)) WS=$(($FALLOC - $FSIZE)) $FSIZE is the file size, $BLKS is the size of each reported block, $NBLK is the number of blocks the file takes, thus $FALLOC is the rounded up block size. For 64K sector size, the BLKS is 512, and BLKS is 128 (one 64K sector). $FALLOC is the correct value of 64K (10K rounded up to 64K). Then the problem comes to how the write is done: _ddt of=$i oseek=$FSIZE obs=$WS count=1 status=noxfer 2>/dev/null & Unfrotunately the above command is using output block size of 54K, and need to skip 10K * 54K bytes, resulting a file size of 540M. So far although it's not the correct intention, it's not yet causing problem. But during _append_file(), we further enlarge the file by: FSIZE=`stat -t $i | cut -d" " -f2` dd if=$X of=$i seek=1 bs=$FSIZE obs=$FSIZE count=1 status=noxfer 2>/dev/null & In above case, since the previous file is 540M size, the output block size will also be 540M, taking a lot of memory. Furthermore since the workload is run in background, we can have many dd processes taking up at least 540M, causing huge memory usage and trigger OOM. [FIX] The original code is already not doing what it should do, just get rid of the cursed dd command usage inside _fill_blk(), and use pwrite from xfs_io instead. Signed-off-by: Qu Wenruo --- tests/btrfs/002 | 14 +++++--------- 1 file changed, 5 insertions(+), 9 deletions(-) diff --git a/tests/btrfs/002 b/tests/btrfs/002 index f223cc60..0c231b89 100755 --- a/tests/btrfs/002 +++ b/tests/btrfs/002 @@ -70,19 +70,14 @@ _read_modify_write() _fill_blk() { local FSIZE - local BLKS - local NBLK - local FALLOC - local WS + local NEWSIZE for i in `find /$1 -type f` do FSIZE=`stat -t $i | cut -d" " -f2` - BLKS=`stat -c "%B" $i` - NBLK=`stat -c "%b" $i` - FALLOC=$(($BLKS * $NBLK)) - WS=$(($FALLOC - $FSIZE)) - _ddt of=$i oseek=$FSIZE obs=$WS count=1 status=noxfer 2>/dev/null & + NEWSIZE=$(( ($FSIZE + $blksize -1 ) / $blksize * $blksize )) + + $XFS_IO_PROG -c "pwrite -i /dev/urandom $FSIZE $(( $NEWSIZE - $FSIZE ))" $i > /dev/null & done wait $! } @@ -118,6 +113,7 @@ $BTRFS_UTIL_PROG subvolume create $firstvol > /dev/null || _fail "btrfs subvolum dirp=`mktemp -duq $firstvol/dir.XXXXXX` _populate_fs -n 1 -f 20 -d 10 -r $dirp -s 10 -c SNAPNAME=0 +blksize=$(_get_block_size $SCRATCH_MNT) _create_snap $firstvol _save_checksum $firstvol $tmp.sv1.sum _verify_checksum $SNAPNAME $tmp.sv1.sum