lecture 2 - file systems under linux

8/9/2019 Lecture 2 - File Systems Under Linux

http://slidepdf.com/reader/full/lecture-2-file-systems-under-linux 1/30

!"#$%&' )"#*+,-./0+%"1#"234&% 56%7-86% 5-6% 9:;'%2

<%&'*"% =>

5-6% ;:;'%2; *4?%" <-4*7

@4?"A B"-4C2344



D*'6-4%

• 5-6% ;:;'%2; *4?%" <-4*7 – 5-6% ;:;'%2; -4 E4-7 F <-4*7 – 9:28#6-& 6-4C; – G#*4H4. #1 I6% ;:;'%2;

• J-"'*36 I6% ;:;'%2 – 9*+%"86#&C – K4#?% – L%4'": #8$%&' – 5-6% #8$%&'

•

M732+6% -2+6%2%4'3H#4 #1 3 I6% ;:;'%2 -4 <-4*783;%? #4 %7'=



E4-7 I6% ;:;'%2;

• !"#$%$&'"&%(

– N"%% ;'"*&'*"% – 5-6% &3'36#.*%; 3; -4'%"436 4#?%; – 5-6%; 3; 6%3O%; – P# "%;'"-&H#4; "%.3"?-4. Q-?'/ 34? ?%+'/

• *+,-"-.#,. – P%3"6: 366 ;:;'%2 #8$%&'; 3"% "%+"%;%4'%? 3; I6%; 34? &34 8% *;%? O-3 '/% I6%

-4'%"13&% RI6%;S &3'36#.*%;S &#22*4-&3H#4 #8$%&';S ?%O-&%;S TTTU – 9:4'3&H&366: %V*36 '"%3'2%4' #1 366 ':+%;S ;%234H&366: 3; 13" 3; +#;;-86% – ,%4&%> @++6-&3H#4; 3"% -4?%+%4?%4' 1"#2 '/% #8$%&' ':+%

• /"01(# – D46: 3 1%QS 8*' W%7-86% I6% #+%"3H#4; – 9-2+6% I6% ;'"*&'*"%

Slide based on Lecture Operating Systems by Prof. Dr. U. Heiss



5-6%; -4 E4-7

•

B:'% ;'"-4.• @"8-'"3"-6: 3??"%;;386%• X#4'%4' /3; 4# +"%?%I4%? +"#+%"H%;• 5#"2 34? &#4'%4' &"%3'%? 8: *;%"• Y%;'"-&'%? '# 3 ;-4.6% 6#.-&36 2%?-*2• !"#'%&'%? 8: 3&&%;; "-./';

– " R"%3?U – Q RQ"-'%U – 7 R%7%&*'%U

• ?%I4%? 1#" *;%"S ."#*+S #'/%";




L-"%&'#"-%; RI6% &3'36#.*%;U

•

L-"%&'#"-%; 3"% /34?6%? 3; 4#"236 I6%;S 8*' 3"% 23"C%? -4 K4#?%0':+% 3; ?-"%&'#":• @ ?-"%&'#": %4'": &#4'3-4;

– <%4.'/ #1 '/% %4'": – P32% RO3"-386% 6%4.'/ *+ '# =\\ &/3"3&'%";U – K4#?% 4*28%"

• G*6H+6% ?-"%&'#": %4'"-%; 23: "%1%"%4&% '/% ;32% K4#?%4*28%" R/3"? 6-4CU

• E;%"; -?%4H1: I6%; O-3 +3'/432%; R]F+3'/F'#FI6%]U '/3' 3"%23++%? '# K4#?% 4*28%"; 8: '/% D9

• K1 '/% +3'/ ;'3"'; Q-'/ ]F]S -' -; 38;#6*'% 34? -; "%;#6O%? *+ 1"#2

'/% "##' ?-"%&'#":• D'/%"Q-;% '/% +3'/ -; "%;#6O%? "%63HO% '# '/% &*""%4' ?-"%&'#":




L-"%&'#"-%;

• M3&/ ?-"%&'#": &#4'3-4; 34 %4'": ]T] '/3'"%+"%;%4'; '/% K4#?% #1 '/% &*""%4' ?-"%&'#":

• N/% ;%&#4? %4'": ]TT^ "%1%"%4&%; +3"%4' ?-"%&'#":

• N/% +3'/ -; "%;#6O%? 1"#2 6%_ '# "-./' 34? '/%"%;+%&HO% 432% -; 6##C%? *+ -4 '/% ?-"%&'#":

• @; 6#4. 3; '/% &*""%4' 432% -; 4#' '/% 63;' -4 '/%+3'/S -' /3; '# 8% 3 ?-"%&'#":T D'/%"Q-;%S '/%

6##C*+ '%"2-43'%; Q-'/ 34 %""#"




9:28#6-& <-4C;• N# -2+"#O% ;/3"%? 3&&%;; '# I6%;S EPK` 366#Q; *;% #1 ;:28#6-& 6-4C; '# "%1%"%4&%

;-4.6% I6%; 34? ?-"%&'#"-%; O-3 2*6H+6% ?-a%"%4' +3'/;• symlink(bisheriger_name, neuer_name) &"%3'%; 34 3??-H#436 +3'/ '# '/%

"%;#*"&%

• M732+6%

3_%" ;:26-4CR]F*;"F;"&F*';F;:;]S]F*;"F-4&6*?%F;:;]U

34? ;:26-4CR]F*;"F-4&6*?%F"%36I6%T/]S]F*;"F;"&F*';F;:;F'%;b-6%T/]U'/%"% %7-;' '/"%% +3'/; '# '/% ;32% I6%

sys

usr

src include

uts

sys

inode.h testfile.h

realfile.h




,3"? 34? 9:28#6-& <-4C;• @'%$2 (",3 -; 34 3??-H#436 I6% 432%

– N/%"% %7-;'; 34#'/%" ?-"%&'#": %4'": '/3' +#-4'; '# '/% ;32% I6% – @66 /3"? 6-4C; +#-4' '# '/% ;32% K4#?% – M3&/ 4%Q /3"? 6-4C -4&"%2%4'; '/% 6-4C &#*4'%" #1 '/% K4#?% – @; 6#4. 3; '/% 6-4C &#*4'%" c dS '/% I6% ];*"O-O%;] 3 "%2#O%RU 34? #46: '/% 6-4C

&#*4'%" -; ?%&"%2%4'%? – K1 '/% 63;' 6-4C -; "%2#O%?S '/% I6% -; ?%6%'%? 34? '/% K4#?% &34 8% "%*;%?

– ,3"? 6-4C; &34 #46: 8% &"%3'%? 1#" I6%; -4 '/% ;32% I6% 6#.-&36 I6% ;:;'%2• @-405+("& (",3 R;#_ 6-4CU -; 3 I6% '/3' &#4'3-4; '/% +3'/ #1 34#'/%" I6% #"

?-"%&'#": – 9:28#6-& 6-4C; 3"% -4'%"+"%'%? 34? "%;#6O%? #4 %O%": 3&&%;; – K1 '/% '3".%' #1 3 ;:28#6-& 6-4C -; ?%6%'%?S '/% 6-4C 8%&#2%; -4O36-? 8*'

"%23-4; %7-;'%4'

– 9:28#6-& 6-4C; '# I6%; 34? ?-"%&'#"-%; &34 8% &"%3'%? 1#" I6%; '/3' ?# 4#' %7-;'R:%'U




<#.-&36 34? !/:;-&36 5-6% 9:;'%2

• @ 6#.-&36 I6% ;:;'%2 23: -;' #1 2*6H+6% +/:;-&36 I6% ;:;'%2;• @ I6% ;:;'%2 &34 8% /##C%? -4'# 34: +3'/ #1 '/% O-"'*36 I6% ;:;'%2 '"%% Q-'/ '/% ]2#*4']

&#2234?

• G#*4'%? I6% ;:;'%2; 3"% 2343.%? 8: '/% D9 -4 3 ]2#*4' '386%] '/3' &#44%&'; +3'/; '#2#*4' +#-4';

• N/-; 366#Q; '# -?%4H1: '/% "##' K4#?%; #1 2#*4'%? I6% ;:;'%2;

bin etc usr

cc sh getty passwd

/

/

bin include src

awk yacc stdio.h uts

mount-point




J-"'*36 5-6% 9:;'%2• N/% J-"'*36 5-6% 9:;'%2 RJ59U -2+6%2%4'; 3 .%4%"-& I6% ;:;'%2 -4'%"13&%

8%'Q%%4 '/% 3&'*36 I6% ;:;'%2 -2+6%2%4'3H#4 R-4 C%"4%6U 34?3&&%;;-4. 3++6-&3H#4; '# +"#O-?% -4'%"#+%"38-6-':

! @++6-&3H#4; &34 3&&%;; ?-a%"%4' I6% ;:;'%2; #4 ?-a%"%4' 2%?-3 O-3 3/#2#.%4%#*; ;%' #1 EPK` ;:;'%2 &366;

Slide based on R. Love: Linux Kernel Development

VFS cpHDD with ext4

DVD with UDF



J-"'*36 5-6% 9:;'%2M732+6%> write(f, &buf, len); • e"-'% #1 len B:'%; -4 I6% Q-'/ ?%;&"-+'#" f 1"#2 B*a%" buf -;

'"34;63'%? -4'# ;:;'%2 &366

• N/% ;:;'%2 &366 -; 1#"Q3"?%? '# '/% 3&'*36 I6% ;:;'%2 -2+6%2%4'3H#4• N/% I6% ;:;'%2 %7%&*'%; '/% Q"-'% &#2234?

sys_write()write() file systemwrite method

User-space VFS File system Disk drive




J59 D8$%&'; 34? L3'3 9'"*&'*"%;

•

J59 -; #8$%&' #"-%4'%?• 5#*" 83;% #8$%&'; – 9*+%" 86#&C> Y%+"%;%4'; ;+%&-I& +"#+%"H%; #1 3 I6% ;:;'%2 – K4#?%> 5-6% ?%;&"-+H#4 – L%4'":> N/% ?-"%&'#": %4'": "%+"%;%4'; 3 ;-4.6% &#2+#4%4' #1 3

+3'/ – 5-6%> Y%+"%;%4'3H#4 #1 34 #+%4 I6% '/3' -; 3;;#&-3'%? Q-'/ 3

+"#&%;;• J59 /34?6%; ?-"%&'#"-%; 6-C% I6%;

– L%4'": #8$%&' "%+"%;%4'; &#2+#4%4' #1 3 +3'/ '/3' 23: 8% 3 I6% – L-"%&'#"-%; 3"% /34?6%? 6-C% I6%; 3; K4#?%;

• M3&/ #8$%&' +"#O-?%; 3 ;%' #1 #+%"3H#4;




9*+%"86#&C

• M3&/ I6% ;:;'%2 2*;'+"#O-?% 3 ;*+%"86#&C• X#4'3-4; +"#+%"H%; #1

'/% I6% ;:;'%2

• K; ;'#"%? #4 ;+%&-36;%&'#"; #1 ?-;C #" -;&"%3'%? ?:432-&366: R-T%T8: ;:;1;U

• 9'"*&'*"% -; &"%3'%? 8:alloc_super() Q/%4'/% I6% ;:;'%2 -;2#*4'%?




K4#?% D8$%&'• X#4'3-4; -41#"23H#4 ;+%&-I& '# 3 I6%

• 5#" ':+-&36 E4-7 I6% ;:;'%2;S 34 K4#?% &34?-"%&'6: 8% "%3? 1"#2 ?-;C

• D'/%" I6% ;:;'%2; /#6? '/-; -41#"23H#4 3; +3"'#1 3 I6% #" -4 3 ?3'383;%! K4#?% /3; '# 8% &"%3'%? 8: '/% I6% ;:;'%2

•

9+%&-36 M4'"-%; 1#" 4#40?3'3 I6%; – -T%Ti_pipe, i_bdev, #" i_cdev 3"%

"%;%"O%? 1#" +-+%;S 86#&C 34? &/3"3&'%" ?%O-&%;

• 9#2% %4'"-%; 3"% 4#' ;*++#"'%? 8: 366 I6%;:;'%2; 34? 23: '/%"%1#"% 8% ;%' '# Null




K4#?% D+%"3H#4;

• K4#?% D+%"3H#4; ?%;&"-8% '/% ;%' #1 #+%"3H#4; '/3' 3"% -2+6%2%4'%?8: '/% I6% ;:;'%2 34? 3"% 3&&%;;%? O-3 J59




L%4'": D8$%&';• E4-7 ?-"%&'#"-%; 3"% /34?6%? 6-C% I6%;

• N/% +3'/ /bin/vi &#4'3-4; '/%?-"%&'#"-%;/ 34? bin 3; Q%66 3; '/%I6%vi

• Y%;#6*H#4 #1 +3'/; "%V*-"%;-4'"#?*&H#4 #1 dentry #8$%&';

• M3&/ +3"' #1 3 +3'/ -; dentry#8$%&'

• J59 &"%3'%;dentry #8$%&'; #4 '/%W:

• P# %V*-O36%4' #4 ?-;C ?"-O%

• @"% ;'#"%? -4 ?%4'": &3&/% R/34?6%?

8: D9U – 5"#4'%4? #1 K4#?% &3&/%




5-6% D8$%&'• 5-6% #8$%&' "%+"%;%4'; #+%4 I6%

• K4'%"13&% '# 3++6-&3H#4;• K; &"%3'%? 3; "%+6: '#open() ;:;'%2 &366

• K; "%2#O%? #4close()

• L-a%"%4' +"#&%;;%; &34 #+%4 3 I6%2*6H+6% H2%; ! ?-a%"%4' I6% #8$%&';

• N/% I6% #8$%&' -; 34 -402%2#":?3'3 ;'"*&'*"% #1 '/% D9




5-6% #+%"3H#4;



,#Q ?#%; D9 I4? 34 K4#?%f

Is it a valid Inode address?

In which group resides Inode

Information about the group

Offset within the group

Read data from disk / from Cache



,#Q ?#%; '/% #; I4? 3 I6%fM732+6%> D+%4-4. '/% I6%/home/user/.profile >

• / -; 36Q3:; ;'#"%? -4 K4#?% = #1 '/% "##' I6% ;:;'%2 – RM7&%+H#4> !"#&%;; Q3;chroot'ed U

• D+%4 K4#?% =S "%3? ?3'3 #1 K4#?%S 6##C*+ %4'":home 34? "%3? -'; -4#?% 4*28%"

• D+%4 K4#?% 1#"home S "%3? -'; ?3'3S 6##C*+ %4'": 1#" user 34? "%3? -'; -4#?%4*28%"

• D+%4 K4#?% 1#"user S "%3? -'; ?3'3S 6##C*+ %4'": 1#" .profile 34? "%3? -'; -4#?%4*28%"

• D+%4 K4#?% 1#".profile S "%3? -'; ?3'3S &"%3'% 3struct file

• @ +#-4'%" '# '/% I6% -; 3??%? '# '/% I6% +#-4'%" '386% #1 '/% D9

! N/% I6% ?%;&"-+'#" '386% #1 '/% &366-4. +"#&%;; -; *+?3'%? Q-'/ '/% 4%Q +#-4'%"

Slide based on presentation from M. J. Dominus



g#*"436-4. 5-6% 9:;'%2;

•

h@ $#*"436-4. I6% ;:;'%2 -; 3 I6% ;:;'%2 '/3' 6#.; &/34.%; '# 3 $#*"436 R*;*366: 3 &-"&*63" 6#. -4 3 ;+%&-366:0366#&3'%? 3"%3U 8%1#"%3&'*366: Q"-H4. '/%2 '# '/% 23-4 I6% ;:;'%2^

• !"#86%2 ?%;&"-+H#4 Q-'/#*' g#*"436-4.> – @ &"3;/%? &#2+*'%" #" I6% ;:;'%2 2-./' 6%3? '# -4-;'%4' ?3'3 #4 3 I6%

;:;'%2

– 5*66 I6% ;:;'%2 4%%?; '# 8% &/%&C%? 34? "%+3-"%?! N/-; +"#&%;; 2-./' '3C% 2*6H+6% /#*";i

! K?%3> – e"-'% 366 ?3'3 '# 3 $#*"436 I";'S '/%4 '# -'; I436 ?%;H43H#4 #4 ?-;C

– D4 3 &"3;/S #46: '/% $#*"436 /3; '# 8% &/%&C%? 1#" *4I4-;/%? '"34;3&H#4;

– D+%"3H#4; &34 8% %7%&*'%? 3'#2-&366:

Slide based on Wikipedia



g#*"436-4. 5-6% 9:;'%2;

•

j 5*66 g#*"436-4.h Q"-'%; 366 ?3'3 'Q-&%! ?%."3?%? +%"1#"234&% • K?%3 #1 jG%'3?3'3 g#*"436-4.h>

– D46: Q"-'% 2%'3?3'3 #1 3 I6% '# '/% $#*"436S 3&'*36 I6% ?3'3 -; ?-"%&'6:Q"-k%4 '# ?-;C

• 5-6% ?3'3 ;/#*6? 8% Q"-k%4 8%1#"% '/% 2%'3?3'3 -; &#22-k%? '#'/% $#*"436 '# +"%O%4' I6% -4-;'%4&-%;

• M732+6%lT Y%;-Z% I6% -4 K4#?%

=T @66#&3'% ;+3&% 1#" I6% %7'%4;-#4 -4 '/% 1"%% ;+3&% 23+

mT e"-'% ?3'3 '# '/% 4%Q6: 366#&3'%? 3"%3 What happens if the computercrashes after step 2?

Slide based on Wikipedia



M`N m g#*"436-4. 5-6% 9:;'%2• M`N m %7'%4?; M`N = 8: $#*"436-4.

• g#*"436 -; ;'#"%? 3; 3 I6% #4 '/% I6% ;:;'%2 8*' 23: 36;# 8% ;'#"%? #4 3 ;%+3"3'% +3"HH#4• g#*"436 -; -2+6%2%4'%? 3; 3 "-4. 8*a%"T K1 '/% #+%"3H#4; 3"% &#22-k%? '# ?-;CS '/% $#*"436 -;

"%*;%?

• g#*"436 ;*+%"86#&C ;'#"%; -41#"23H#4 6-C% 86#&C ;-Z% 34? +#-4'%"; '# '/% 8%.-44-4.34? '/% %4? #1 '/% $#*"436

• g#*"436 ?%;&"-+'#" 86#&C 23"C; '/% 8%.-44-4. #1 3 '"34;3&H#4 34? &#4'3-4;-41#"23H#4 38#*' 1#66#Q-4. 86#&C;S -T%T '/%-" ;'#"3.% 6#&3H#4

• g#*"436 &#22-' 86#&C -; Q"-k%4 '# '/% %4? #1 3 '"34;3&H#4T K1 '/% gXB Q3; Q"-k%4S '/%

'"34;3&H#4 &34 8% "%&#O%"%? Q-'/#*' ?3'3 6#;;

Slide based on V. Prabhakaran et al.: Analysis and Evolution of Journaling File Systems



M`N m g#*"436-4. G#?%;

M`N m +"#O-?%; '/"%% ?-a%"%4' $#*"436-4. 2#?%;• e"-'%083&C

– D46: '/% 2%'3?3'3 -; Q"-k%4 '# '/% $#*"436

– L3'3 86#&C; 3"% ?-"%&'6: Q"-k%4 '# ?-;C – P# &6%3" #"?%"-4. #1 Q"-'%; #1 ?3'3 86#&C; #" '/% $#*"436

–

@ &"3;/ 23: 6%3? '# 34 -4-;'%4' ;'3'%• D"?%"%?

– D46: 2%'3?3'3 -; Q"-k%4 '# '/% $#*"436 – L3'3 86#&C; 3"% Q"-k%4 '# ?-;CS 8%1#"% 2%'3?3'3 -; Q"-k%4 '# '/% $#*"436

– K1 2%'3?3'3 Q"-'% &#22-';S '/%4 '/% ?3'3 -; -;'%4' 3_%" &"3;/

• L3'3 – L3'3 34? 2%'3?3'3 3"% Q"-k%4 '# '/% $#*"436

Slide based on V. Prabhakaran et al.: Analysis and Evolution of Journaling File Systems



M`N m g#*"436-4. G#?%;



M`N m N"34;3&H#4;

• N"34;3&H#4; – M`N m ."#*+; 2*6H+6% I6% ;:;'%2 *+?3'%; -4'# 3 ;-4.6%

'"34;3&H#4 – )#36> !%"1#"234&% -2+"#O%2%4' -1 3 ;'"*&'*"% -; *+?3'%?

2*6H+6% H2%;

– M732+6%> 5"%% ;+3&% 8-'23+ -; *+?3'%? "%.*63"6:

• X/%&C+#-4H4. – 56*;/%; $#*"436-4. -41#"23H#4 '# 8% Q"-k%4 '# '/%-" ?%;H43H#4

86#&C;

– N"-..%"%? 8: 3 H2%"S -1 I6% ;:;'%2 8*a%"; 8%&#2% '# ;2366S #"'/% $#*"436 "%3&/%; -'; 237-2*2 ;-Z%



Y%;%"O3H#4 #1 B6#&C; -4 M`Nm• !"%0366#&3H#4 #1 86#&C; /%6+; '#

"%?*&% 1"3.2%4'3H#4 #1 I6%;• M`Nm ;*++#"'; "%;%"O3H#4 #1

3"%3; -4 '/% 23-4 2%2#":• M3&/ K4#?% /3; -'; #Q4

"%;%"O3H#4 Q-4?#Q – e-4?#Q; ?# 4#' #O%"63+

– e-4?#Q; &34 ."#Q 34? ;/"-4C?:432-&366:

– e-4?#Q; 3"% "%2#O%? -1 '/% I6% -;&6#;%?

! K2+"#O%? '/"#*./+*'



Y%;%"O3H#4 #1 B6#&C; -4 M`Nm

lecture 2 - file systems under linux

Documents