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Add documentation for --ghost-fiemap

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The --ghost-fiemap option was introduced with #1963.

It enables an optimized algorithm based on fiemap ioctl that can reduce
the number of syscalls used to checkpoint highly sparse ghost files. This
option is enabled by default. It can be disabled with --no-ghost-fiemap
when using SEEK_HOLE/SEEK_DATA is preferred. In addition, an automatic
fallback to SEEK_HOLE/SEEK_DATA is used for filesystems that do not
supporting fiemap.

Co-authored-by: Pavel Tikhomirov <ptikhomirov@virtuozzo.com>
Signed-off-by: Radostin Stoyanov <rstoyanov@fedoraproject.org>
This commit is contained in:
Radostin Stoyanov 2023-02-23 12:55:01 +00:00 committed by Andrei Vagin
parent 4a8c02d636
commit 50e42c9ddc
2 changed files with 8 additions and 0 deletions
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7
Documentation/criu.txt
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@ -384,6 +384,13 @@ mount -t cgroup -o devices,freezer none devices,freezer
'size' may be postfixed with a *K*, *M* or *G*, which stands for kilo-, 'size' may be postfixed with a *K*, *M* or *G*, which stands for kilo-,
mega, and gigabytes, accordingly. mega, and gigabytes, accordingly.
*--ghost-fiemap*::
Enable an optimization based on fiemap ioctl that can reduce the
number of system calls used when checkpointing highly sparse ghost
files. This option is enabled by default, and it can be disabled
with *--no-ghost-fiemap*. An automatic fallback to SEEK_HOLE/SEEK_DATA
is used when fiemap is not supported.
*-j*, *--shell-job*:: *-j*, *--shell-job*::
Allow one to dump shell jobs. This implies the restored task will Allow one to dump shell jobs. This implies the restored task will
inherit session and process group ID from the *criu* itself. inherit session and process group ID from the *criu* itself.

1
criu/crtools.c
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@ -445,6 +445,7 @@ usage:
" is inaccessible\n" " is inaccessible\n"
" --link-remap allow one to link unlinked files back when possible\n" " --link-remap allow one to link unlinked files back when possible\n"
" --ghost-limit size limit max size of deleted file contents inside image\n" " --ghost-limit size limit max size of deleted file contents inside image\n"
" --ghost-fiemap enable dumping of deleted files using fiemap\n"
" --action-script FILE add an external action script\n" " --action-script FILE add an external action script\n"
" -j|--" OPT_SHELL_JOB " allow one to dump and restore shell jobs\n" " -j|--" OPT_SHELL_JOB " allow one to dump and restore shell jobs\n"
" -l|--" OPT_FILE_LOCKS " handle file locks, for safety, only used for container\n" " -l|--" OPT_FILE_LOCKS " handle file locks, for safety, only used for container\n"