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vfs_vnops.c: Use va_bytes >= va_size hint to avoid SEEK_DATA/SEEKHOLE

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vn_generic_copy_file_range() tries to maintain holes
in file ranges being copied, using SEEK_DATA/SEEK_HOLE
where possible,

Unfortunately SEEK_DATA/SEEK_HOLE operations can take
a long time under certain circumstances.
Although it is not currently possible to know if a file has
unallocated data regions, the case where va_bytes >= va_size
is a strong hint that there are no unallocated data regions.
This hint does not work well for file systems doing compression,
but since it is only a hint, it is still useful.

For the case of va_bytes >= va_size, avoid doing SEEK_DATA/SEEK_HOLE.

Reviewed by:	kib
MFC after:	2 weeks
Differential Revision:	https://reviews.freebsd.org/D44509
This commit is contained in:
Rick Macklem 2024-03-14 17:35:32 -07:00
parent 6a6ec90681
commit 89f1dcb3eb
1 changed files with 26 additions and 8 deletions
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34
sys/kern/vfs_vnops.c
View file

@ -3334,14 +3334,15 @@ vn_generic_copy_file_range(struct vnode *invp, off_t *inoffp,
struct vnode *outvp, off_t *outoffp, size_t *lenp, unsigned int flags,
struct ucred *incred, struct ucred *outcred, struct thread *fsize_td)
{
struct vattr inva;
struct mount *mp;
off_t startoff, endoff, xfer, xfer2;
u_long blksize;
int error, interrupted;
bool cantseek, readzeros, eof, lastblock, holetoeof;
bool cantseek, readzeros, eof, lastblock, holetoeof, sparse;
ssize_t aresid, r = 0;
size_t copylen, len, savlen;
off_t insize, outsize;
off_t outsize;
char *dat;
long holein, holeout;
struct timespec curts, endts;
@ -3357,11 +3358,26 @@ vn_generic_copy_file_range(struct vnode *invp, off_t *inoffp,
goto out;
if (VOP_PATHCONF(invp, _PC_MIN_HOLE_SIZE, &holein) != 0)
holein = 0;
error = vn_getsize_locked(invp, &insize, incred);
error = VOP_GETATTR(invp, &inva, incred);
if (error == 0 && inva.va_size > OFF_MAX)
error = EFBIG;
VOP_UNLOCK(invp);
if (error != 0)
goto out;
/*
* Use va_bytes >= va_size as a hint that the file does not have
* sufficient holes to justify the overhead of doing FIOSEEKHOLE.
* This hint does not work well for file systems doing compression
* and may fail when allocations for extended attributes increases
* the value of va_bytes to >= va_size.
*/
sparse = true;
if (holein != 0 && inva.va_bytes >= inva.va_size) {
holein = 0;
sparse = false;
}
mp = NULL;
error = vn_start_write(outvp, &mp, V_WAIT);
if (error == 0)
@ -3395,9 +3411,9 @@ vn_generic_copy_file_range(struct vnode *invp, off_t *inoffp,
error = vn_getsize_locked(outvp, &outsize, outcred);
if (error == 0 && outsize > *outoffp &&
*outoffp <= OFF_MAX - len && outsize <= *outoffp + len &&
*inoffp < insize &&
*outoffp <= OFF_MAX - (insize - *inoffp) &&
outsize <= *outoffp + (insize - *inoffp)) {
*inoffp < inva.va_size &&
*outoffp <= OFF_MAX - (inva.va_size - *inoffp) &&
outsize <= *outoffp + (inva.va_size - *inoffp)) {
#ifdef MAC
error = mac_vnode_check_write(curthread->td_ucred,
outcred, outvp);
@ -3415,7 +3431,7 @@ vn_generic_copy_file_range(struct vnode *invp, off_t *inoffp,
if (error != 0)
goto out;
if (holein == 0 && holeout > 0) {
if (sparse && holein == 0 && holeout > 0) {
/*
* For this special case, the input data will be scanned
* for blocks of all 0 bytes. For these blocks, the
@ -3486,7 +3502,7 @@ vn_generic_copy_file_range(struct vnode *invp, off_t *inoffp,
error = VOP_IOCTL(invp, FIOSEEKDATA, &startoff, 0,
incred, curthread);
if (error == ENXIO) {
startoff = endoff = insize;
startoff = endoff = inva.va_size;
eof = holetoeof = true;
error = 0;
}
@ -3549,6 +3565,8 @@ vn_generic_copy_file_range(struct vnode *invp, off_t *inoffp,
cantseek = false;
} else {
cantseek = true;
if (!sparse)
cantseek = false;
startoff = *inoffp;
copylen = len;
error = 0;