Hi:
I was surprised to see a few write operations called into ext4_dax_huge_fault
with FAULT_FLAG_WRITE set on vmf->flags
Are those writes expected at all?
static int ext4_dax_huge_fault(struct vm_fault *vmf,
enum page_entry_size pe_size)
{
...
bool write = vmf->flags & FAULT_FLAG_WRITE;
Based on the following Mount documentation below, I did mount this ext fs with
ro and noloadAre there any other options that I could use to totally eliminate
those unexpected writes?
- -r, --read-only
- Mount the filesystem read-only. A synonym is -o ro.Note that, depending
on the filesystem type, state and kernel behavior, the system may still write
to the device. For example, Ext3 or ext4 will replay itsjournal if the
filesystem is dirty. To prevent this kind of write access, you may want to
mount ext3 or ext4 filesystem with "ro,noload" mount options or setthe block
device to read-only mode, see command blockdev(8).
-
Related DMESG output...
[ 0.891653] EXT4-fs (pmem0): DAX enabled. Warning: EXPERIMENTAL, use at your
own risk
[ 0.892736] EXT4-fs (pmem0): mounted filesystem without journal. Opts:
noload,dax
[ 0.898293] EXT4-fs (sda): mounted filesystem without journal. Opts: (null)
[ 0.902574] random: fast init done
[ 0.926157] IPVS: ftp: loaded support on port[0] = 21
// My private debug messages
[ 0.997224] EXT4-fs (pmem0): write is 1 handle = 0xffffffffffffffe2
<--read-only device
[ 0.998052] EXT4-fs (pmem0): write is 1 handle = 0xffffffffffffffe2
[ 0.998787] EXT4-fs (pmem0): write is 1 handle = 0xffffffffffffffe2
[ 0.999720] EXT4-fs (pmem0): write is 0 handle = 0x0
[ 1.004626] EXT4-fs (pmem0): write is 0 handle = 0x0
[ 1.005359] EXT4-fs (pmem0): write is 0 handle = 0x0
[ 1.006128] EXT4-fs (pmem0): write is 0 handle = 0x0
[ 1.006824] EXT4-fs (pmem0): write is 0 handle = 0x0
[ 1.007499] EXT4-fs (pmem0): write is 0 handle = 0x0
[ 1.008149] EXT4-fs (pmem0): write is 0 handle = 0x0
[ 7.320626] random: crng init done
[ 18.780447] EXT4-fs: 53 callbacks suppressed
[ 18.781900] EXT4-fs (pmem0): write is 0 handle = 0x0
[ 18.783392] EXT4-fs (pmem0): write is 0 handle = 0x0
[ 18.790661] EXT4-fs (pmem0): write is 0 handle = 0x0
[ 18.792042] EXT4-fs (pmem0): write is 0 handle = 0x0
[ 18.793321] EXT4-fs (pmem0): write is 0 handle = 0x0
[ 18.795005] EXT4-fs (pmem0): write is 0 handle = 0x0
[ 18.795204] EXT4-fs (pmem0): write is 1 handle = 0xffffffffffffffe2
[ 18.795209] EXT4-fs (pmem0): write is 1 handle = 0xffffffffffffffe2
[ 18.795213] EXT4-fs (pmem0): write is 1 handle = 0xffffffffffffffe2
[ 18.795257] EXT4-fs (pmem0): write is 0 handle = 0x0
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